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Rate of Crypto Outbreaks Doubles from 2014 to 2016

MAY 23, 2017 | EINAV KEET
The Centers for Disease Control and Prevention (CDC) is observing Healthy and Safe Swimming Week from May 22 to 28 this year, emphasizing ways to prevent outbreaks of the parasitic infection Cryptosporidium, in swimmers.

The microscopic parasite Cryptosporidium, commonly known as “crypto,” can infect animals, and some Cryptosporidium species can also infect humans. This is the leading cause of water-borne disease in humans in the United States. Due to the parasite’s protective outer shell, Cryptosporidium can live outside of a host for a prolonged period time and even persist in chlorinated pools when an infected person or animal sheds the parasite through their stool; therefore, contaminated pools and other recreational water locations are a common source of the parasite.

Symptoms related to a Cryptosporidium infection include watery diarrhea, stomach cramps, nausea, dehydration, vomiting, fever, and weight loss, and usually begin within 2 to 10 days after infection. While symptoms can continue for up to 30 days, infected individuals shed the parasite once their symptoms begin and can continue to do so for weeks after the symptoms have subsided.

A recent study published in the Morbidity and Mortality Weekly Report detailed CDC surveillance data and noted that the United States had experienced at least 32 aquatic facility–associated Cryptosporidiosis outbreaks in 2016, which is double the number of outbreaks reported in 2014. The report focused on outbreaks in Alabama, Arizona, and Ohio, with each state experiencing Cryptosporidiosis outbreaks last year, and highlight the recent surge in Cryptosporidiosis. Last year, Ohio saw 1,940 infections after reporting a median of 399 cases each year from 2011 to 2015. Arizona’s 2016 rate of 352 laboratory-confirmed cases, which occurred between July 1 and October 31, far outnumbers the median 46 cases the state has reported annually from 2011 to 2015. Using molecular diagnostic methods to detect the species and subtypes of the parasite responsible for the outbreaks, Alabama and Arizona health officials reported that the outbreaks were caused by the C. hominis IfA12G1R5 subtype of the parasite, while tests on specimens collected in the Ohio revealed that the the C. hominis IdA19 subtype – which has been rarely detected in the United States – is the culprit behind the outbreaks.

Due to the high chlorine tolerance of Cryptosporidium, the CDC recommends that officials in charge of pools and other facilities found to carry the parasite follow hyperchlorination water treatment guidelines in the event of fecal contamination or an outbreak. The CDC also urges anyone infected to avoid pools and other water facilities. “To help protect your family and friends from Crypto and other diarrhea-causing germs, do not swim or let your kids swim if sick with diarrhea,” said the Chief of the CDC’s Healthy Swimming Program, Michele Hlavsa, RN, MPH, in a recent press release.  She also noted that Cryptosporidium can live for up to 10 days in properly treated water and that drinking even a mouthful of contaminated water can lead to illness. “Protect yourself from getting sick by not swallowing the water in which you swim,” she stressed.

In addition to pools, Cryptosporidium can be found in soil, food, water, or surfaces contaminated with infected animal or human feces. To protection oneself from infection, the CDC recommends the public avoid potentially contaminated pools and water sources among other infection prevention practices, especially for those with weakened immune systems, as they are most susceptible to serious illness if exposed to Cryptosporidium.
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