This story started as one of those many news articles that come across a feed. About 40 students and staff sick with gastroenteritis at three neighboring schools in Sacramento, California at the beginning of May. Most of the cases were at one school, and it wasn’t a very large outbreak, compared to other events we have covered here (28, or 1 out of every 6 of our blog posts has been about a school or university norovirus outbreak). There were also reports of possible cases at the University of California Davis, and another 40 students sick in neighboring Yolo County.
Things quieted down in the news for a while, yet twelve days ago on May 13th, suddenly the case count in Yolo was almost 1000. Two days later, when the number hit 2000, forty of the 65 public schools in Yolo County had been affected, and about 200 students and staff were also ill in Sacramento County schools. Two days ago, there were reports of 3,200 cases in Yolo County, with some elementary districts having 25 to 30% of their students out sick.
The Yolo County Health and Human Services Agency, as well as the Sacramento County Health Department have been working with the schools since the early days to prevent the spread of illness. The focus has been on students staying home for 48 hours after their symptoms resolve, increased handwashing, and thoroughly disinfecting surfaces. Compounding the issue are end-of-school-year activities, such as final exams and graduation ceremonies, which may prompt kids going back to school while they are still quite contagious.
While impressive, the numbers shouldn’t have been all that surprising, considering how good norovirus is causing a fast and expansive swath of misery. The incubation period is about 12-48 hours, and so if an infected person spreads the virus to even a couple of other people, the numbers can go up quickly. And while grouped by location, it has been unclear in the articles whether the different sets of outbreaks are related (i.e., being caused by the exact same virus). That is the sort of question to be answered by genetic testing and epidemiological sleuthing, which can take a little time.
For example, in mid-May, ten schools and about 200 students in the San Jose Unified School District, 100 miles from the Yolo and Sacramento Cases, were also affected by norovirus. At about the same time as the first students were falling ill in Yolo County, a private boarding school outside of Los Angeles, almost 400 miles away in Ventura County, had to close for cleaning after over 70 students and 15 staff were sick. Were these related to a larger whole?
Again, it will be interesting to learn more about the epidemiology of this event, and hopefully as the academic year comes to a close and prevention measures are implemented, the case numbers will fall.