Fun, Friends, and Norovirus Down at the Good Old Swimming Hole

Paul G. Auwaerter, MD


August 18, 2015

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I am Paul Auwaerter, with the Division of Infectious Diseases at Johns Hopkins University School of Medicine.

I was asked to evaluate a young man recently who had a rather severe gastrointestinal illness without fever but lots of nausea and vomiting. It also affected a couple of his friends and family. None required hospitalization.

Most people view winter as the time when people are most susceptible to infection, but many potential infectious agents are more common during the summer, and these need consideration.

Gastrointestinal illness would make you think of a certain flavor of illness, but there are many summertime infections. Historically, poliovirus is what our parents' generation and earlier feared most; but it is no longer an issue due to the vaccine. Enteroviral infections remain common and can cause fever with rashes (such as hand, foot, and mouth disease), especially in children. Summer can also bring aseptic meningitis, gastroenteritis, arboviruses, mosquito-borne infections (with West Nile virus being in the lead), and other, more sporadic infections. We see tickborne illnesses (Lyme disease, Rocky Mountain spotted fever, and others) and respiratory pathogens, which can spread in such communal settings as summer camp (parainfluenza virus type 3, adenovirus, or mycoplasma). Swimmer's ear is a rather pedestrian problem, but there are also rare but serious and devastating infections, such as amebic meningoencephalitis.

Concerns for gastrointestinal illness include such causes as Vibrio, Aeromonas, and Plesiomonas, which are more common during the summer compared with more traditional foodborne infections; however, the Centers for Disease Control and Prevention[1] reminds us that foodborne infections generally are about two times more common during the summer, perhaps because of inadequate food handling practices at picnics and fairs. They affect 1 in 6 Americans annually, so it is a significant problem.

A newer issue has been norovirus, a leading cause of foodborne illness and known for many years to be a cause of infection through water exposure (going back to the 1980s).[2] A report from Oregon last summer[3] described more than 70 people with a sudden gastrointestinal illness, and a small number of these were confirmed to be norovirus infections. The common risk factor was swimming in a certain recreational lake. We would not normally think of norovirus from a swimming exposure. Going down to the swimming hole has to join the list of potential exposures to not only the traditional coliforms (such as E coli and others) but also norovirus.

There is no way for public health authorities currently to assess risks for norovirus in public (fresh) waters. The presence of E coli is used as the surrogate. Of interest, public health officials didn't know how long to keep this lake closed after detection of norovirus because the virus can live for days, weeks, or even months and be fairly durable. Of course, changes in the water, exposure, and dissipation may be variables. The thought was that either fecal matter or vomit contaminated the water in this case.

Unfortunately, summertime "innocence at the swimming hole" may not be quite what it was in the past. Clinicians have to ask about swimming exposures, church picnics, and so on. Our patient had gone on a picnic with family and friends and they also went swimming. We were unable to uncover the illness by any diagnostic methods, but it seemed compatible with the kind of illness that would be caused by norovirus, and it made me think of these other cases. It might prompt polymerase chain reaction testing for norovirus in stool specimens, especially because several other people were ill as well.

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