Norovirus outbreak reported in three Sacramento County schools

William T. Gerson, MD

As general pediatricians, we are quite familiar with viral gastroenteritis in all its diverse presentations and wide-ranging complications; practicing in a resource-rich country, we are generally able to recommend effective supportive measures for these usually self-limited illnesses with no available effective antiviral agents.

We see in the office far less cases than we hear about over the phone. The utilization of reasonably clear guidelines for telephone triage allows the identification of those infants, children and young adults with underlying medical conditions that place patients at increased risk of complications and those with evidence of volume depletion – of course, identification of those with other diagnoses but similar symptoms as viral gastroenteritis can be challenging.

Perhaps one disadvantage of practicing in a resource-rich country is the overutilization of intravenous rehydration despite decades of evidence of the superiority of oral rehydration in all except those with the most severe dehydration; additionally, continuation of breastfeeding during diarrhea and the resumption of an age-appropriate diet, excluding high fats and simple sugars once patients are rehydrated are encouraged.

The use of a single oral dose of odansetron has been shown to stop the vomiting associated with viral gastroenteritis in children and decrease the progression to the need for intravenous fluids; however, its use should not be considered a routine component of management of the vomiting associated with these illnesses. The use of probiotics/prebiotics for management of the diarrheal component of viral gastroenteritis is common, but data on the superiority of specific agents in cases of gastroenteritis in which the specific viral agent is unknown are limited.

 Norovirus is the most common viral etiology in epidemic gastroenteritis worldwide and, since the introduction of the rotavirus vaccine, it is the most common cause of gastroenteritis in adults and children in the United States. In pediatric offices, we can help identify noroviral infection since it is distinctly characterized by occurrence in outbreaks with short incubation times (24-48 hours), abrupt onset, a majority of affected cases with vomiting, and an average duration of illness of 12-60 hours. Public health colleagues should be involved early in the investigation of these situations and to add their particular expertise in epidemic management and control.

As the closing of Sacramento schools demonstrate it is not just cruise ships that can be crippled by such outbreaks. General pediatricians are likely to be involved in many – if not all – aspects of a norovirus outbreak. Closing a school dramatically affects a community: While ensuring the well-being of students and staff, closures can confuse, disrupt, alienate, and in some ways, increase anxiety over school safety if not done in a professional and compassionate manner. Attention to issues of health information privacy is required. Resource allocation to school districts and best practice implementation for classrooms, health offices and cafeterias are also critical. It is humbling to remember that proper hand washing, though critical in halting the spread of many diseases, is very difficult to achieve, particularly in most school settings.

Pediatricians are likely to be asked not only about specifics of management of affected individuals in norovirus outbreaks, but also about control of spread and return to school recommendations. Norovirus spread is primarily via the fecal-oral route, although airborne droplet spread from vomitus, fomite contamination, and contaminated food and water also can be involved.

Prevention is challenging as limiting exposure to infected persons in the community setting is extremely difficult given asymptomatic transmission particularly in children: the difficulties involved in assuring good handwashing (soap and water, as alcohol-based hand sanitizers have little effect on norovirus); the association with food services (a universal feature of schools), and; the fact that norovirus is extremely stable in the environment, able to resist freezing and heating as well as disinfection with alcohol or standard cleaning agents. Transmission also requires a small inoculum size (<100 particles) thus making outbreak control even more arduous.

Reasonable guidelines for return to school are important to reinforce. Prolonged shedding of virus in stool is common although it is maximal in the first 24-48 hours. Obviously the more restrictive the return to school recommendations are the less risk to other children. However, the real-world implications of prolonged school absence are complex. Resolution of diarrhea and vomiting are the minimal criteria.

AAP recommendations define resolution of diarrhea as less than two stools greater than the child’s normal stool frequency and vomiting resolution as less than twice in the preceding 24 hours. Additionally, children in diapers should be excluded if the stool cannot be contained in their diapers, or, in older children, if they are having stool accidents using the toilet. Reminding families to use soap and water to wash hands after using the toilet, as well as after changing diapers or contaminated clothing, is also essential.