Norovirus - the global hitchhiker

Norovirus image

Vomiting, often in projectile form, diarrhoea, muscle and head aches and a churning stomach which lasts a day or two - the symptoms of Norovirus, arguably one of the most common human pathogens on the planet and for which there is no known treatment or vaccine. Norovirus is particularly prevalent during Winter months and highly infectious as exposure to as few as 17 virus particles can lead to infection in comparison to almost 1,000 which are needed for influenza to take hold.

For an RNA virus, Norovirus is very resilient being able to withstand most chemical detergents, freezing and heating up to 600C. It can also survive for up to 2 weeks on hard surfaces such as doorknobs and  tablecloths. There are around 40 identified strains. One study in 2009 the Netherlands which examined a jamboree which had been over-run by Norovirus found that for every person who fell sick, fourteen others were infected. These are startling rates of transmission and account for the speed at which Norovirus epidemics can quickly move to pandemics. Norovirus has two main groups (termed genogroups) which afflict humans - GI and GII - within each of these are viral variants with GII.4 currently having the greatest mutation capacity.  The mutation capability of Norovirus is what makes it hard for the immune system to identify the pathogen  and attack it.

With the Winter season now in full swing in the Southern Hemisphere, the global hitchhiker is bound to make its appearance. In 2012, Novovirus GII.4 Sydney progressed to world -wide infection with a substanial impact on the United Kingdom.