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Crypto Outbreaks in Aquatic Facilities

Left to right: Cryptosporidium in the oocyst stage; emerging from its resistant shell; fully emerged
Photo courtesy of the Centers for Disease Control & Prevention

 

Over 250 people in central Ohio and over 100 in Arizona have been sickened in summer outbreaks of cryptosporidiosis, a diarrheal illness caused by the microscopic parasite Cryptosporidium, or “Crypto.” These parasites are found throughout the US and abroad, and settle in the intestines of infected humans and animals, making Crypto one of the most well-known zoonotic diseases. According to the Centers for Disease Control & Prevention (CDC), millions can be released in the feces of an infected person. Only 10 to 30 are needed, however, to cause infection in a healthy person, according to Yoder and Beach (2010).1

Crypto spreads in aquatic facilities when people inadvertently swallow water contaminated with the feces of infected individuals. Understanding Crypto and how to avoid infection can help your family enjoy the fun and health benefits of swimming pools and other aquatic facilities.

Chlorine Resistance

Crypto is the leading cause of recreational water outbreaks in the US. You may be wondering why chlorine, a mainstay of swimming pool treatment, doesn’t destroy Crypto. The gold standard for disinfectants, chlorine helps reduce the public’s exposure to a wide array of waterborne bacteria, viruses and parasites. Crypto, however, is chlorine-resistant as a result of the protective shell of the parasite’s “oocyst” stage, the stage at which it is shed in the feces of those infected (see photo above). Crypto can survive in water at CDC-recommended chlorine levels (1–3 mg/L) and pH (7.2–7.8) for over 10 days, according to Shields et al. (2008)2 . The protective shell also allows Crypto to survive outside the body for long periods of time.

Temporarily elevating chlorine levels in Crypto-contaminated swimming pools—a process known as super-chlorination—can destroy the parasite, but it must be done when the facility is closed to swimmers.3 Crypto infections may spread regionally when infected swimmers who are unwilling to wait for a pool to reopen following super-chlorination visit neighboring pools. Pool water filtration is another strategy for removing Crypto. The factors affecting the efficiency of removal of Crypto and other parasites by filtration is an important subject of ongoing study. According to CDC’s Model Aquatic Health Code, UV (ultraviolet) radiation (light sanitization) following filtration may be the most cost-effective disinfection strategy (see the Code’s Annex, p. 131). UV inactivates Crypto so that it can no longer reproduce.

Cryptosporidiosis Symptoms

Symptoms of cryptosporidiosis include: watery diarrhea, stomach cramps or pain, dehydration, nausea, vomiting, fever and weight loss. Some people with cryptosporidiosis have no symptoms at all, and may unknowingly spread the illness in aquatic facilities. Symptoms are likely to last from one to two weeks, but can persist sporadically for up to 30 days. Immunocompromised persons may develop “serious, chronic, and sometimes fatal illness,” according to CDC. Such people include people with AIDS, those with inherited diseases that affect the immune system, and cancer and transplant patients who are taking certain immunosuppressive drugs.

Most people with healthy immune systems recover from cryptosporidiosis without treatment. CDC reports Nitazoxanide may be prescribed for treatment of diarrhea caused by Crypto in people with healthy immune systems. Nitazoxanide is not approved for treatment of immunodeficient individuals because it has not been shown to be effective for that population.

Tips for Reducing Your Risk of Cryptosporidiosis at Aquatic Facilities

Remember the saying, “When Swimming, Don’t Discount Sanitary Conditions”

  • Wash hands thoroughly after using the bathroom, and instruct children to do the same.
  • Shower with soap and water (especially the perianal area) before entering the aquatic facility.
  • Diarrhea: Do not use aquatic facilities if you are experiencing diarrhea; if you were diagnosed with cryptosporidiosis, do not use aquatic facilities until two weeks after diarrhea has stopped.
  • Diaper Changing: Do not change diapers poolside; use designated facilities, and wash hands thoroughly afterwards.
  • Swallowing water: Avoid swallowing water while in the aquatic facility.
  • Children: Take young children on frequent bathroom breaks (every hour); check diapers frequently (every 30–60 minutes).

The tips above are important, not only for the residents of Ohio and Arizona who are experiencing Crypto outbreaks currently, but for everyone who frequents aquatic facilities. Don’t wait for an outbreak—help avoid one!

Chris Wiant, M.P.H., Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council.

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1 Yoder, J.S. and Beach, M.J. (2010). Cryptosporidium surveillance and risk factors in the United States. Experimental Parasitology 124:31–39.

2 Shields, J.M., Hill, V.R., Arrowood, M.J., and Beach, M.J. (2008). Inactivation of Cryptosporidium parvum under chlorinated recreational water conditions. Journal of Water and Health 6:513–520.

3 A recent update to the Model Aquatic Health Code recommends that for Crypto inactivation in pools (that use cyanuric acid stabilizer), a dosage of 20 ppm free chlorine is needed for 28 hours, representing a doubling of the previous concentration x time, or “CxT” recommendation.

Your Guide to Removing Swimming Pool Stains

The swimmers at the summer games inspired awe in all who viewed those exciting events, including the littlest backyard pool athlete who has dreams of winning gold.  Recently, the sparkling blue of the dive pool in Rio was transformed into a deep green, sparking fears of algae.  In fact, the color change was blamed on a decline in alkalinity, caused by insufficient levels of chemicals that buffer pool water pH.  A significant drop in pH can make the water corrosive to metal fixtures and equipment, which could cause metal leaching and discoloration of the water.

If you are maintaining a backyard pool for your family, you may be wondering about the appearance of stains in your pool – not only in the water, but on pool surfaces.  What causes them and how should they be treated?  A recent article1 by Terry Arko in The IPSSAN (The Independent Pool & Spa Service Association, Inc., July, 2016) newsletter provides many helpful answers.

As Arko notes, “Not all stains are the same, so it’s important to diagnose the stain before providing a broad-spectrum treatment.”  Arko also makes the point that when addressing a pool stain, the first thing to do is to ensure the water chemistry is balanced.  He notes, “A lot of staining in pools is from the pH dropping down and aggressively dissolving the metals into solution.”  Regarding pool surfaces, vinyl and fiberglass pools usually respond better to stain treatment than plaster pools, which are more porous.  The quality of paint on plaster, concrete or cement plastered pools also affects how easily stains are removed.  Arko recommends brushing pool walls regularly and adding a sequestering agent (to prevent metal staining) at a frequency (e.g., weekly, biweekly, or monthly) that fits your needs.

The table below is based on Arko’s recommendations for specific pool stain removal:

Stain Color Likely Source Treatment Notes
Blue-green stain on pool surfaces or in water (but water is not cloudy) Copper from algaecides, heat exchangers, fill water, older copper plumbing Granular treatments, such as citric acid and ascorbic acid used directly on the stain; an additional sequestering agent can help the filtration system trap removed metals.  If treatment includes phosphoric and/or phosphonic acid, these must be removed at a later time.  Generally, non-phosphate treatments are only effective on stains that have not yet set into the surface. If water is blue-green and also cloudy, the likely source of the stain is algae, in which case an algaecide is needed; algae will also be evident by slimy walls and floor.

In the Rio dive pool example, the alkalinity of the pool water had to be restored with chemicals such as sodium bicarbonate and sodium carbonate.

Purple precipitate on pool water surface, tile line, skimmers and pool cleaner Copper cyanurate when the cyanuric acid level is over 100 ppm Reduce cyanuric acid level to about 50 ppm by draining water. Draining water also addresses copper in the water, but it is important to test the water for any remaining copper.
Brown stain on pool surfaces or in water The most common source is well water that contains dissolved iron or manganese; other potential sources are pool heater headers or lawn fertilizers Same as for copper; if the source of iron is well water, begin a maintenance program of adding a sequestering agent weekly; use a non-phosphate sequestering agent to preclude elevating phosphate levels.
Brown stains, some of which may be shaped like leaves and other organic debris Leaves and other natural materials that settle to the pool bottom; often found after uncovering the pool at the start of pool season Stains may disappear as pool chlorine levels are established or shock treatment is applied; alternatively, citric acid or ascorbic acid work well to lift these stains.
Metal corrosion Salt generators corrode metals, such as pool ladders and light rings Add a sacrificial anode, such as zinc; use a non-phosphate sequestering agent.

 

Bruce Bernard, PhD, is President of SRA Consulting, Inc., and Associate Editor of the International Journal of Toxicology, and lives in Cambridge, MD.


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1 “Pool staining—identify before you treat,” by Terry Arko, The IPSSAN, July, 2016, p. 9, 13, and 17.

 

 

How to Interpret Pool Chlorine Readings

Pool chlorine levels are easily measured by dipping a test strip in the pool for a few seconds and then matching the resulting color of the strip to a chart linked to “parts per million” chlorine levels. Here’s the rub: Some pool test kits measure “free chlorine,” whereas others measure both “free chlorine” and “total chlorine.” There is a difference between “free” and “total” chlorine. That may be breaking news to an investigative reporter who recently confused the two in a news segment about possible contaminants in swimming pools.

Why Measure Chlorine?

This summer, the Centers for Disease Control and Prevention (CDC) is recommending the public check the chlorine level and pH of pool water before enjoying a refreshing swim. Why? A new CDC report finds that one in five pools in five states in 2013 had to be closed due to serious safety violations, including improper pH or chlorine readings. That prompted an investigative reporter for NBC News and the Today show, to measure pathogen and chlorine levels at several public aquatic facilities. At one pool, the reporter described a “sky-high” total chlorine reading of 10 parts per million. He compared the reading to the appropriate range of free chlorine levels (1-3 parts per million), saying, “Three is ideal, so it is way over.” Needless to say, that created consternation in the news room, not to mention fear and confusion among the viewing public.

There’s Chlorine, and Then, There’s Chlorine!

Without getting too technical, the reading that is a measure of how much chlorine is available in pool water to destroy germs is known as the free chlorine level. But not all chlorine in the pool is available to destroy germs. As the Water Quality and Health Council discussed in its article of May 27, 2016, some chlorine may be unavailable because it has chemically reacted with impurities brought into the pool on the bodies of swimmers. Chlorine that reacts with swimmer perspiration, urine, body oils and cosmetics produces “combined chlorine,” which is mostly unavailable to destroy germs.

The total chlorine level is the sum of the free chlorine and combined chlorine levels in the pool. Reporting a total chlorine level of 10 parts per million, as the reporter did, only tells us that the free chlorine level is likely less than that.

Total Chlorine = Free Chlorine + Combined Chlorine.

I hope this explanation helps you interpret chlorine level reports! This summer, you can order a free pool test kit—that measures pool water free chlorine and pH—at www.healthypools.org.

Linda F. Golodner is President Emeritus of the National Consumers League and Vice Chair of the Water Quality & Health Council.

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Maximizing Healthy Fun in the Kiddie Pool

Each summer, parents of toddlers and young children delight in introducing their offspring to the kiddie pool.  With its shallow water, plastic pails and inflatable toys, the kiddie pool is a haven of fun, discovery and social interaction for the youngest pool patrons.  Spending time in the kiddie pool to acclimate a toddler to the water could be the first step in cultivating a life-long swimmer. All terrific!

Now for the disturbing news:  According to a new report from the Centers for Disease Control and Prevention (CDC), of all the aquatic venues that were closed because of serious health and safety violations in 2013, kiddie and wading pools lead the pack.  Specifically, in the five US states with the most public pools, one in five wading pools (20 percent) had to be closed immediately upon inspection due to serious health and safety violations.

The Diaper Set

It probably comes as no surprise that the diaper set provides specific challenges to pool water quality.  CDC reports, “Young children are more likely to experience acute gastrointestinal illnesses…and are more likely to contaminate the water because they either are incontinent or have inadequate toileting and hygiene skills.” Unfortunately, there is no such thing as a leak-proof diaper, and they do leak. CDC also notes that “as much as 10 grams of fecal material can rinse off a young child’s perianal surface and into the water.”  Add to this the fact that discovery for toddlers is often linked to tasting, or in this case, drinking pool water, and we have a potentially risky combination of factors.

Better Water Quality in the Kiddie Pool

The most frequently reported violations in wading pools in 2013 involved disinfectant level, pH and automated chemical feeder violations.  Given the water quality challenges associated with kiddie pools, this is a significant finding that can help inform solutions.  Here’s our best advice to parents and care-givers of young children at the kiddie pool:

  • Don’t allow your child into the pool unless you have checked the pool water quality. Some pools post inspection results online.  Alternatively, you can be your own pool inspector and obtain instant readings. Use a pool test kit to ensure the pH and free chlorine level of the water are within acceptable ranges. If readings are outside of the acceptable range, lose no time in approaching the pool manager.  This summer you can order a free pool test kit at healthypools.org.
  • Keep sick children and those experiencing diarrhea out of the pool.
  • Change swim diapers frequently in the restroom, and take children who are newly potty-trained to the restroom at frequent intervals.
  • Teach children not to drink pool water.

Water play in the kiddie pool is a fun, social activity for very young children.  Rather than discouraging parents and care-givers from visiting these venues, we recommend reaping the benefits of the kiddie pool by actively managing the risks.

Chris Wiant, M.P.H., Ph.D., is president and CEO of the Caring for Colorado Foundation. He is also chair of the Water Quality & Health Council.

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Swimming Pool Water: When Clarity Counts

A new Centers for Disease Control and Prevention (CDC) report states that one in eight swimming pool inspections in five states in 2013 resulted in immediate closure due to serious health and safety violations. Is it any wonder that officials with CDC are asking swimmers to be their own pool inspectors this summer?  The agency adds that only 68 percent of US local public health agencies regulate, inspect, or license public aquatic facilities. CDC’s response is to turn swimmers into their own pool inspectors by providing them with an inspection checklist:

  • Is the pool chemistry correct?  Use a simple pool test kit to check the water’s pH and free chlorine level. (Get a free pool test kit at www.healthypools.org.)
  • Is the drain at the bottom of the deep end visible?
  • Do the drain covers at the bottom appear to be secured and in good repair?
  • Is a lifeguard on duty?  If not, is safety equipment available (e.g., rescue ring or pole)?

The near-drowning incident was written up in the local newspaper.

Getting the pool chemistry right (the first item on the checklist) contributes to a healthy and comfortable swim.  Confirming the next three items on the checklist can be a matter of life and death.  I speak from experience, the memory of which came flooding back to me while reading the checklist.

Saved in the Deep End of the Pool

Following my high school graduation in 1966, I worked as a lifeguard at a local community pool in Texas. One late afternoon in August I was seated in a lifeguard chair near the deep end of the pool, when I glanced down into the water and saw a girl lying on the bottom. Instantly considering and dismissing the possibility of a prank, I plunged in and pulled out the unconscious 15-year old from a depth of about eight feet.  After boosting the girl’s limp form onto the pool deck, I heard someone yell, “There’s another one down there.” Back I went into the water and brought up a 12-year old girl.

Once on the pool deck, I administered mouth-to-mouth resucitation to the younger girl.  She was revived quickly, but the 15-year old was turning blue despite the life-saving efforts of my fellow lifeguards. Finally, the older girl was revived by a fire department unit that was called. Both girls survived the ordeal, and as I indicated to a newspaper reporter who later interviewed me, at the end of the day, I was grateful that I had been trained in Red Cross senior life-saving.  This near double drowning also points out the importance of learning how to swim to prevent drowning.

I am convinced that my story might have had a diffent ending if the pool water had been murky.  Being able to see to the floor drain at the deep end of the pool is the ultimate test of pool clarity—clear vision through the greatest depth of water in the pool.  Remember:  If swimmers in trouble can’t be seen, they can’t be saved.  CDC’s swimmer checklist is a significant tool that can help save lives this summer.

Ralph Morris, MD, MPH, is a Physician and Preventive Medicine and Public Health official living in Bemidji, MN.

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The Truth about Chlorine in Swimming Pools

This summer when you don your bathing suit and walk out onto the pool deck, you may be in for a sensory experience that conjures up happy memories of summers past—warm sunshine, sparkling pool water and the smell of chlorine.  If the chlorine smell is very strong, however, you may soon spot “red-eyed” swimmers emerging from the pool.  That’s when the pool water is assumed to have “too much chlorine” in it.  Ironically, a strong chemical smell around the pool and “swimmer red eye” may be signs that there is not enough chlorine in the water.  Sound confusing?  It’s time to set the record straight about chlorine and swimming pools.

Chlorine helps protect swimmers from waterborne germs

Most swimmers understand that chlorine is added to pools to kill germs that can make swimmers sick.  Chlorine-based pool sanitizers help reduce swimmers’ risk of waterborne illnesses, such as diarrhea, swimmer’s ear, and various skin infections.  The great advantage of chlorine over other sanitizers, such as ozone and UV is that it keeps working long after it is added to pool water; chlorine provides a “residual” level of protection against germs in the water.  Chlorine is not the only “game in town” when it comes to pool sanitizers, but of the common products, only chlorine- and bromine-based disinfectants provide significant residual protection.  Salt-water pools, by the way, are chlorinated pools in which the chlorine is generated on site from sodium chloride.

It’s important to get the pool chemistry right

Pool managers strive to keep the “free chlorine” level of pool water between about one and three parts per million.  Maintaining the chlorine level in that range depends on several factors, including the pH of the water (it should be between 7.2 and 7.8), and the presence of unwanted substances in the pool, such as urine, perspiration, body oils and lotions, which compete with chlorine and react with it.  These substances add to what is known as the “chlorine demand.”

Products of chemical reactions between chlorine and substances added by swimmers are irritants known as chloramines.  It is chloramines, not chlorine, that are responsible for swimmer red eye.  Unshowered and unhygienic swimmers (read:  those who pee in the pool), add to the “chlorine demand” and are often the real cause of swimmer red eye.  Unfortunately, as chlorine reacts with impurities brought into the pool by swimmers, there is less of it available to kill germs.  So, not only do unhygienic swimmers promote irritants forming in swimming pools, they may also inadvertently raise the risk of waterborne illnesses.  More chlorine may be needed to chemically destroy the chloramines formed and restore a free chlorine residual.

Swimmers can help keep swimming healthy

This comes as a surprise to many swimmers.  The fact is that swimmer hygiene affects the chemistry of the pool and the comfort of swimmers.  Last summer we made the point that swimmer “red eye” is an indicator that someone might have peed in the pool.  That raised awareness and quite a few eyebrows.  This year, we join our efforts to those of the Centers for Disease Control and Prevention and ask swimmers to shower before swimming and never pee in the pool.  When you walk out to the pool this summer, sniff the air and decide whether or not you are about to jump into a healthy pool!

Want to know if you have adequate chlorine in the pool?  Order a free pool test kit at www.healthypools.org today!

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That “Chemical Smell” at the Pool Isn’t What You Think It Is

For America’s Most Fun Form of Summer Exercise, Experts Urge Swimmers to Use Senses to Stay Healthy at the Pool

As Americans jump into another fun-filled summer of swimming, a new survey finds that most don’t know the real reason why some pools have a strong chemical smell. A survey conducted on behalf of the Water Quality and Health Council found that three-quarters of Americans incorrectly believe that the chemical odor they smell at pools is a sign that there’s too much chlorine in the water.

Experts at the Water Quality and Health Council, U.S. Centers for Disease Control and Prevention (CDC), and the National Swimming Pool Foundation® (NSPF®) said properly treated swimming pools do not have a strong chemical smell. However, when chlorine in pool water combines with pee, poop, sweat, and dirt from swimmers’ bodies, chemical irritants called chloramines1 are produced. These chloramines give off a chemical odor, cause eyes to get red and sting, and use up the chlorine, meaning there is less to kill germs.

“It’s understandable why most people think that a chemical smell means there is too much chlorine in the pool, but the truth could be the opposite,” said Chris Wiant, Chair of the Water Quality and Health Council. “To help prevent chloramines from forming where you swim, shower before swimming and take little swimmers on regular bathroom breaks.”

Experts from the Water Quality and Health Council, CDC, and the NSPF are advising swimmers to use a “Sensible Checklist” to ensure a fun and healthy swimming experience:

  • Are the pH and chlorine level correct? Use a test strip to check.
  • Standing at the edge of the pool, can you see the drain in the bottom of the deep end?
  • Do drain covers on the bottom of the pool appear to be secure and in good repair?
  • Is a lifeguard on duty? If a lifeguard is not on duty, is safety equipment (for example, a rescue ring or pole) available?
  • Is the area around the pool free of strong chemical odors?

“Swimming is proof that exercise can be fun if you just add water,” said Thomas M. Lachocki, Ph. D., CEO of NSPF. “It’s not just a form of fun exercise though. Swimming is a lifetime survival skill. Learning to swim should become a priority for all parents and adults, not only could their children become healthier for it, but they could also save someone’s life someday.”

Getting the Word Out

The Water Quality and Health Council is once again making free test kits available this summer through their Healthy Pools campaign. Swimmers can test their backyard or community pool to ensure it has proper pH and chlorine level. To order a free test kit offered as part of the Water Quality and Health Council’s award winning summer Healthy Pools campaign, please go to www.healthypools.org.

The National Swimming Pool Foundation would like to encourage adults to find swimming classes for themselves and their children through swimtoday.org. Learning to swim today, can improve your health and save a life tomorrow.

To learn more about healthy and safe swimming, check out CDC’s new Healthy Swimming website at www.cdc.gov/healthyswimming.

The survey was conducted online by Survata, an independent research firm in San Francisco. Survata interviewed 1,500 adults May 12-13, 2016 and has a margin of error of 2.5%.


1 These chloramines are different from the type of chloramine that is sometimes used to treat drinking water.

2 The survey was conducted by Survata, an independent research firm in San Francisco. Survata interviewed 1,500 online respondents between (TBD) and (TBD). The margin of error for the survey is 2.53%.

Lifecycle of the Zika-transmitting Mosquito

Mosquito borne illnesses have played a significant role the course of human history and continue to have repercussions on human health. The World Health Organization (WHO) calls the mosquito the “greatest menace” of all disease-transmitting insects, responsible for several million deaths and hundreds of millions of cases every year.  Malaria alone, transmitted by Anopheles mosquitoes, caused 438,000 deaths in 2015 and sickened 214 million people globally, according to the World Malaria Report (2015).  Historically, it was “a leading obstacle to Africa’s colonization,” note the authors of a National Academies Press book on the

Four stages in the life cycle of mosquitoes Image courtesy of the US Centers for Disease Control & Prevention website

economics of malaria drugs.1 “It struck US presidents from Washington to Lincoln, weakened Civil War soldiers by the hundreds of thousands…traveled to California with the Gold Rush and claimed Native American lives across the continent.”2

The Aedes aegypti mosquito transmits a host of illnesses, from Zika virus and yellow fever to dengue and chikungunya.  The YouTube video and photo above clearly illustrate the four life stages of the Aedes aegypti mosquito, from eggs to adults.  Understanding the Aedes aegypti mosquito life cycle is key to understanding how to control it.

The “Container-breeding Mosquito”

Standing water is the perfect environment for mosquito breeding because it is where the larvae develop.  As summer approaches and Zika virus transmission risk rises, health officials are asking the public to remove even small amounts of standing water.  According to a US Centers for Disease Control and Prevention (CDC) blog, the Aedes aegypti mosquito “likes to lay eggs in water that collects or is stored in manmade containers.”

A Multi-front Defense
Besides removing standing water, shore up your defenses against mosquitoes this summer by using a CDC-approved insecticide, such as DEET, picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol. Lightweight, long-sleeved shirts and long pants also can help protect you from mosquito bites, particularly while spending extended periods of time outdoors. Finally, be sure that window and door screens are in good repair.

We recommend dumping standing water after no more than two days from 3:

Vases

Pet Water Bowls

Flowerpots/Saucers

Buckets

Pool and Boat Covers

Birdbaths

Uncovered Trash Cans/Indented Lids

Rain Barrels

Toys

Garden Ornaments that Collect Water

 

Other Mosquito Control Strategies

The Mosquito Control Association recommends changing the water in birdbaths and wading pools at least once per week, and stocking ornamental pools with “top feeding predacious minnows,” which eat mosquito larvae.  Alternatively, ornamental pools may be treated with biorational larvicides (active against a given target, but relatively innocuous to non-target organisms), or S-methoprene-containing (insect growth regulators) products.  Chlorine solutions are also known to inhibit mosquito larvae development, probably through an insect growth regulator mechanism.  Research is being conducted to determine effective solution concentrations.

Discarded tires can be a mosquito breeding paradise.  Avoid storing these outdoors, but if no other options are available, these can be treated with a larvicide.

****

Additional Tips for backyard swimming pool owners:

  • Empty the water from small inflatable and molded plastic kiddie pools immediately after use.
  • Keep larger pools properly chlorinated to inhibit mosquito breeding. Leaving to go on vacation?  See to it that the pool is treated while you are away, or cover the pool.

 

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1 Institute of Medicine (US) Committee on the Economics of Antimalarial Drugs; Arrow KJ, Panosian C, Gelband H, editors. Washington (DC): National Academies Press (US); 2004. On line, available:  http://www.ncbi.nlm.nih.gov/books/NBK215638/

2 Ibid.

3 Based on the CDC blog, “Zika Virus:  Zika, Mosquitoes, and Standing Water,” posted March 22, 2016.  Online, available:  http://blogs.cdc.gov/publichealthmatters/2016/03/zikaandwater/

Preparing for the Summer of Zika Virus

Fig. 1. U.S. map showing 1) Ae. aegypti potential abundance for Jan/July (colored circles), 2) approximate maximum known range of Ae. aegypti (shaded regions) and Ae. albopictus (gray dashed lines), and 3) monthly average number arrivals to the U.S. by air and land from countries on the CDC Zika travel advisory. Additional details can be found in the text. Figure reproduced with permission of PLOS Currents Outbreaks.

 

Are you curious about your risk of contracting Zika virus this summer?  The figure above is from a brand new study1 on the projected spread of the Aedes aegypti mosquito, the main Zika virus “vector”2. Based on meteorological models, mosquito-breeding patterns, air travel and socioeconomic status, the study compares the January, 2016 abundance of the mosquito (upper hemisphere of each circle) in each geographical location with its projected abundance this July (lower hemisphere of each circle).  The area of each circle is proportional to the estimated monthly average arrivals of people to the US from countries on the Centers for Disease Control and Prevention (CDC) travel advisory list.

The researchers project the greatest concentration of the Aedes aegypti mosquito in the US this summer will be throughout the Gulf Coast states and along the eastern seaboard as far north as New York City, a destination of many arrivals from countries on the CDC Zika travel advisory.  In fact, the circle for New York City is approximately the same size as the one for Miami.

Zika Virus to Date

As of early spring, 2016, virtually all of the known Zika virus infections in the US have been acquired during travel to other countries. Many Zika-infected individuals travelled to Latin America and the Caribbean, where there are Zika virus pandemics.  In Florida, where I am an Environmental Administrator in the Florida Department of Health (FL DOH), we have documented 67 cases of travel-related Zika virus.  Texas has had 27 confirmed cases, including one believed to have been sexually transmitted.  With the northern migration of the Aedes aegypti mosquito carrier this summer, however, Zika virus could soon be transmitted in the US.

The FL DOH and other state and county health departments in Zika virus-vulnerable areas are in full response mode.  States of emergency have been declared in 12 Florida counties,3 and Florida has a mosquito control district operating in every county. Having worked at the FL DOH for over 30 years, I know we will harness the lessons learned in the past fighting other mosquito borne illnesses, such as Eastern Equine Encephalitis and Dengue Fever.  We will inevitably learn a few new tricks as we turn our attention to Zika.  We already have a robust communication plan around this public health threat.

What Florida is Doing to Fight Zika

Daily Zika Updates:  Each day at 2 pm EDT, the Florida DOH issues an online Zika update and press release, identifying new Zika cases, making recommendations, and providing links to additional information.

Tips for Residents:  The Florida DOH website “encourages Florida residents and visitors to protect themselves from all mosquito borne illnesses by draining standing water; covering their skin with repellent and clothing; and covering windows with screens.”  See our “Drain and Cover” web page for more information, including keeping pool chemistry maintained.  Appropriate pH and chlorine levels will help avoid swimming pools becoming breeding grounds for mosquitoes.

Tips for Travelers:  The Florida DOH website advises travelers to tropical and sub-tropical regions can protect themselves from Zika virus and other mosquito borne illnesses by using appropriate insect repellent, covering skin with long-sleeved shirts and long pants, and keeping mosquitoes out of hotel rooms by choosing a hotel with air conditioning or window screens or sleeping under a mosquito bed net.  Our website notes that pregnant women should consider postponing travel to areas of Zika virus transmission.

Basic Information on Zika virus:  Zika is transmitted through the bite of infected Aedes aegypti mosquitoes. Perinatal (mother to child in the weeks just before or just after birth) and sexual transmission have also been reported.

 As summer approaches, stay tuned to public health communications on Zika virus so that you can make decisions and take actions to help protect your family.

 

Bob G. Vincent is an Environmental Administrator in the Florida Department of Health. He manages Department of Health programs for Healthy Marine Beaches, Safe Drinking Water, Water Well Surveillance and Public Pools and Bathing Places.

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1 Monaghan AJ, Morin CW, Steinhoff DF, Wilhelmi O, Hayden M, Quattrochi DA, Reiskind M, Lloyd AL, Smith K, Schmidt CA, Scalf PE, Ernst K. “On the Seasonal Occurrence and Abundance of the Zika Virus Vector Mosquito Aedes Aegypti in the Contiguous United States,” PLOS Currents Outbreaks. 2016 Mar 16 . Edition 1. doi: 10.1371/currents.outbreaks.50dfc7f46798675fc63e7d7da563da76.

2Disease vectors, according to the World Health Organization, are “living organisms that can transmit infectious diseases between humans or from animals to humans.”  In addition to Zika virus, the Aedes aegypti is a vector for Chikungunya, Dengue fever, Rift Valley fever and Yellow fever.

3 Alachua, Brevard, Broward, Hillsborough, Lee, Miami-Dade, Orange, Osceola, Polk, Santa Rosa, Seminole and St. Johns Counties

Zika Virus: On the Move

Zika virus is being actively transmitted by mosquitoes in Brazil, Paraguay, Bolivia, Ecuador, Columbia, Venezuela, Curacao, Guyana, French Guyana, Suriname, Mexico, Guatemala, Honduras, El Salvador, Nicaragua, Panama, Haiti, Dominican Republic, US Virgin Islands, St. Martin, Puerto Rico, Guadeloupe, Martinique and Barbados.

The Zika virus, a flavivirus1, is spreading “explosively” through several Latin American and Caribbean countries, according to the World Health Organization (WHO), prompting that group to declare an international health emergency which, according to the BBC “…means research and aid will be fast-tracked to tackle the infection.”  The virus is transmitted through the bite of the Aedes aegypti and Aedes albopictus mosquitoes, the same mosquito that, according to WHO, transmits dengue, chikungunya and yellow fever.  The virus was identified in the Zika forest of Uganda in 1947 in rhesus monkeys, then in humans in Uganda and the United Republic of Tanzania in 1952.  Recently, Zika virus was reported in Chile in 2014, followed by Brazil in 2015.  Currently the virus is being transmitted actively in over 20 countries.  As of yet, there is no reported active transmission of the virus in the US, but some travelers have returned to the US infected with Zika virus.  As CDC notes, “Any travelers visiting or returning to parts of the United States with established populations of Aedes aegypti or Aedes albopictus mosquitoes could initiate local virus transmission.”

Health Effects of Zika Virus

The Zika virus is spread mainly by the Aedes Aegypti mosquito. Mosquitoes breed in stagnant water and, unchlorinated pools and water storage tanks.

The US Centers for Disease Control and Prevention (CDC) notes that one in every five people infected with Zika virus will become sick for up to one week with fever, rash, joint pain and “nonpurulent” conjunctivitis (“pink eye” without the pus).  That means that 80 percent of people infected have no symptoms, but are carriers of the virus.

Zika virus testing is not widely available.  It is performed only at the CDC Arbovirus Diagnostic Laboratory and a few state health departments, according to CDC.  Test results can be misleading (false positive) if the individual in question was previously infected with another flavivirus, such as dengue, or has been vaccinated against yellow fever or Japanese encephalitis.

Pregnant women who are infected with the virus can pass it on to their unborn children.  There is a question, based on preliminary data from countries such as Brazil , as to whether those children may be at risk for microcephaly, a condition of abnormally small heads that is associated with underdevelopment of the brain.  Studies are needed to clarify whether there is an association between Zika virus infection and microcephaly and Guillain-Barre syndrome.

Pregnant women or women who may become pregnant should not travel to outbreak areas.  Meanwhile, the virus continues to spread at an alarming rate, and there is neither a vaccine for its prevention nor anti-viral medications for treating symptoms.   Research on Zika virus is just beginning, and new information will likely be revealed in the weeks and months ahead.

Maintain Chlorine Levels in Swimming Pools and Water Storage Tanks to Help Prevent Mosquito Breeding

Mosquitoes breed in standing water, not just the puddles and pools remaining following a rainstorm, but any still water that is not intentionally made inhospitable to breeding. For that reason, it is important to maintain appropriate chlorine levels in swimming pools and water storage tanks.

Swimming pool water should be chlorinated in the range of 1-4 parts per million (ppm) and stored drinking water chlorine levels should be kept above 1 ppm free chlorine. This measure not only helps prevent mosquito-breeding, but also helps prevent a host of waterborne illnesses that can be contracted from bacteria and other pathogens in water.

Preventing Zika Virus TransmissionStrategies to prevent mosquito breeding and human exposure to mosquitoes are our best bet for preventing the virus transmission.  These include:

  • Eliminating standing water in flower pots, buckets, barrels, old tires, untreated kiddie pools and other containers that can serve as breeding grounds for mosquitoes.
  • Ensuring good drainage of water around homes.
  • Maintaining a chlorine residual of about 1 mg/l in stored treated drinking water; drinking water storage is common in developing countries that lack central water distribution.
  • Making sure backyard pools are appropriately chlorinated as mosquitoes will not breed in chlorinated water.
  • Inspecting and repairing window and door screens.
  • Applying an insect repellent to exposed skin and/or clothing when spending time outdoors. The Aedes aegypti mosquito bites during daytime hours. Products containing DEET, picaridin, IR3535, and some products containing oil of lemon eucalyptus and para-menthane-diol may provide long-lasting protection; follow label directions for use.2
  • Applying insect repellent to skin after applying sunscreen, if sunscreen is to be used.
  • When you are outdoors, air movement around your body (from fans or natural breezes) disrupts mosquito flight and reduces your risk of being bitten.

 

Ralph Morris, MD, MPH, is a Physician and Preventive Medicine and Public Health official living in Bemidji, MN.

Fred M. Reiff, P.E., is a retired official from both the U.S. Public Health Service and the Pan American Health Organization, and lives in the Reno, Nevada area.
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1 Flaviviruses, according to CDC, are a family of positive, single-stranded, enveloped RNA viruses that cause widespread illness and death.  They are found primarily in ticks and mosquitoes and can occasionally infect humans.  Flaviviruses include Yellow Fever, Dengue Fever, Japanese encephalitis, West Nile viruses and Zika virus.

2 For more information on insect repellents and their effectiveness, please see http://cfpub.epa.gov/oppref/insect/.