NEWS & EVENTS

The profile of a pathogen - Norovirus

PROFILE - 15TH DECEMBER 2016

Norovirus first announced itself to the scientific community (and some unfortunate children) in 1968 through an outbreak of a severe stomach bug in a school which saw almost 40% of nine to 11-year-olds falling sick.

After investigating the outbreak in the Norwalk-Bronson elementary school in Norwalk, Ohio, the US Centers for Disease Control and Prevention announced that the cause was an unknown virus. After a further outbreak, it was officially identified in 1972 by Dr Albert Z Kapikian, who named it the ‘Norwalk virus’.

The virus in question turned out to be one of a group of connected viruses which were given the genus name norovirus, and this has become the most popular way of referring to it. Together they are a group of non-enveloped, single-stranded RNA viruses that cause acute gastroenteritis, and belong to the larger family called caliciviridae. There are six recognised norovirus genogroups, of which three—GI, GII, and GIV—can affect humans. More than 25 different genotypes have been identified within these three genogroups.

The virus causes inflammation of the lining in the stomach and large intestine and is the main cause of gastroenteritis illness in the world. The virus is frequently transmitted through contaminated food, but it can also infect people through contact with an infected object or surface. Because they can be spread through a simple handshake or other close contact, noroviruses thrive on cruise ships, in schools, restaurants, nursing homes—anywhere people exist in close proximity. One of the reasons for their widespread occurrence is that the viruses are extremely tough, as well as highly contagious.

A person usually develops symptoms between 12 to 48 hours of being exposed: sudden vomiting, which is sometimes quite violent (leading to it being known as the ‘winter vomiting bug’), accompanied by nausea, non-bloody diarrhea and abdominal cramps. Some people may have a low-grade fever, headaches and aches all over the body. This usually lasts from 24 to 72 hours, and the vast majority of sufferers recover completely. The exception is people with compromised immune systems, such as those with an existing illness, young children and the elderly. For these groups, severe dehydration can occur, leading to very serious illness and even death.

Since there are so many types of norovirus, a person cannot develop an effective immunity. It is possible to develop some immunity to a specific virus, but this does not last a lifetime. There is no known cure for norovirus, so you just have to let it run its course—rest, drink plenty of liquids to prevent dehydration and possibly take some medication to help with the aches and pains.

The best—and possibly worst—thing about norovirus is that in most cases, how awful it feels is disproportionate to how ill you actually are, and the effects can disappear just as swiftly as they arrived. You will, however, be left feeling wrung out, exhausted and, due to the wide variety of ways you can be infected, cheated of even the psychological satisfaction of pointing the somewhat shaky finger of blame with any great confidence.