Oh Noro!

"Food poisoning." "Stomach flu." The go-to reason for calling in "sick". Unfortunately, there are those that really should call out of work that aren't. Norovirus is the #1 leading cause of disease outbreaks from contaminated food in the U.S., 70% of which is caused by infected food workers.

Not all food poisoning is caused by norovirus (other germs and chemicals share the honor), and it's not related to the Haemophilus influenza (the long name for the flu). It does cause the inflammation of the stomach and intestines (acute gastroenteritis), leading to stomach pain, nausea, non-bloody, watery diarrhea, and acute-onset vomiting lasting for 24-72 hours. Some people present with a low-grade fever, headaches, and myalgias (body aches), and dehydration is the most common complication. It can be caught again and again, and can be serious for young children and older adults.

Transmission electron micrograph of norovirus virions
Image courtesy of CDC

Noroviruses, previously called Norwalk-like viruses, are a group of non-enveloped, single-stranded RNA viruses of the family Calciviridae. Three of the six currently recognized norovirus genogroups, GI, GII, and GIV, infect humans. The most common type causing infection since 2002 is the variants of the GII.4 genotype. The virus is shed through feces once symptoms begin, and continue to do so for 2 weeks or more after recovery (although this does not necessary mean they are contagious).

Norovirus can be spread by contact with an infected person, touching contaminated surfaces, or eating or drinking contaminated foods or water. It has a tendency to spread quickly in closed places like daycare centers, nursing homes, schools, and cruise ships. It is a hardy virus, able to stay on food at freezing temperatures and on kitchen surfaces and utensils for up to two weeks.  It's also resistant to many common disinfectants and hand sanitizers, and only requires 18 viral particles to make you sick.



There is currently no medicine that can treat norovirus, but is manageable with plenty of liquids (not cafffinated or alcoholic beverages) to replace fluid lost from vomiting and diarrhea.  It is preventable through sanitation techniques for both the general public and food service employees, outlined in the infographic below.