In a summer already characterized by extreme heat and a surplus of ticks, we didn’t need an outbreak of a nightmare stomach bug. But here we are, with the highest ever count of cyclosporiasis cases in a season.
It’s an illness caused by consuming the eggs of the microscopic Cyclospora parasite, usually as a result of contaminated produce or water.
This surge in cases has gotten a lot of attention, in part because infection with the parasite causes terrible bouts of diarrhea. Google searches for “cyclospora” have spiked more than 5,000 percent over the past month. Fellow parents keep asking me if they should stop feeding their children raspberries or lettuce.
That’s understandable, because no one wants these symptoms. But a look at the numbers suggests that you can probably chill out a bit.
Our collective freakout about the parasite tells us something important about how we process information and evaluate risk about disease.
The number of documented cases — even with this highest number ever — is really quite small.
The Centers for Disease Control and Prevention has reported 1,645 confirmed cases since May 1 and is aware of an additional 5,100 suspected cases that need more analysis. By contrast, the agency this year has reported nearly 35,000 cases of Campylobacter infection, which is another serious diarrheal illness.
Both of these pale in comparison to the likely number of norovirus cases. While the CDC doesn’t track norovirus cases individually (because they are so numerous), it estimates that up to 21 million Americans a year get sick from the virus, more than 100,000 are hospitalized, and nearly 1,000 die.
Cyclospora can last a lot longer than norovirus or Campylobacter — sometimes a month or longer. But it also usually resolves on its own and is treatable with antibiotics. Deaths are very rare, and it’s not contagious from person to person.
Cases are much higher than usual in a handful of states, with Michigan and Ohio appearing to be the biggest outliers.
But in much of the rest of the country, cases appear to be flat or only modestly elevated relative to a typical year.
Summer always brings some isolated cases of Cyclospora. In California, the Department of Health has reported 41 cases, versus 80 during the same period last year. In Connecticut, cases are higher than usual, but that means 35 cases as of earlier this week, versus 19 last year at this time. That’s roughly one case for every 100,000 people.
To be clear: The case counts could go up, and it’s appropriate to pay attention. The data is woefully incomplete, which is the first big obstacle to understanding the scope of the problem.
Already, Michigan is reporting far more cases within the state than the CDC has confirmed for the whole country — a result of the lag time it takes for the federal agency to collect state numbers.
Every year, this illness is likely undercounted. Watery diarrhea is a very common problem. It can be caused by all kinds of things, and people mostly suffer at home.
In a typical year, many of the people with Cyclospora infection will never get tested or learn they had it.
