Norovirus

Introduction

When someone is infected with norovirus, the virus mainly affects the small intestine. The disease is usually self-limiting, with symptoms including: nausea, vomiting, diarrhea, and abdominal pain. Lethargy, weakness, headaches and muscle aches, and fevers may occur. 

Hosts

Humans and Animals.

Transmission / Exposure Route

Noroviruses are transmitted directly from person to person and indirectly by contaminated water and food. They are extremely contagious, so when the infected vomit, it can be aerosolized. 

Case Fatality Ratio

Severe illness is rare; although there have been instances of hospitalization. In the United States, there have been around 300 deaths a year. These deaths occurred mainly in the very young, the elderly, and immunocompromised individuals. In developing countries, it is associated with 1.1 million hospitalizations, with an estimated 218,000 deaths. 

Incubation Period

The average incubation period for norovirus infections are 12 to 48 hours, with a median period of approximately 33 hours.

Microbiology

Norovirus is a single stranded RNA, non-enveloped viruses. There are many genogroups of noroviruses, the most prevalent in humans are: G I, II, and IV. The diameters of the capsid vary, from 23-40 nm. 

Enviromental Survival

They are relatively stable in the environment and can survive freezing and heating to 60 degrees Celsius.