Winter is probably the only time people will forgive you for talking in hyperbole. Such quips as "struck down by flu", "a fate worse than death" and "lying on their deathbed" are only really tolerated with sympathy at this time of year. Some of you may even be reading this from your very own sickbed: as the news about oysters reminds us, 'tis the season to be sick. More specifically, to catch norovirus – and you don't have to eat seafood to fall ill. The commonly known "winter vomiting bug" is the leading cause of food-borne disease outbreaks and non-bacterial gastroenteritis worldwide. It accounts for 3m cases and 130,000 GP consultations annually.
The norovirus, or norwalk virus, named after the first place the virus was discovered (Norwalk, Ohio) – an RNA virus whose genome undergoes continual change – is a persistent problem at this time of year. With a genome 400,000 times smaller than your own, the virus will incapacitate you for the better part of your long weekend. As with all bugs of this nature it can cause significant morbidity and mortality among the most vulnerable, namely, children, the elderly, and the immuno-compromised. They can experience a more persistent and severe set of symptoms, including dehydration, weight loss, renal failure, chronic diarrhoea for years, malnutrition and even death.
The good news is that, for most, it doesn't last long – no more than 60 hours in the majority of cases. The bad news is the nausea, vomiting, watery diarrhoea, abdominal pain or cramps, loss of appetite, malaise and low-grade fever. Always a good thing at this time of year.
In reality, the virus isn't restricted to winter. It can turn up any time, anywhere. Oh, let me count the ways: outbreaks occur among those who visit restaurants, military personnel, travellers to developing countries, passengers of cruise ships and residents of healthcare facilities, nursing homes, hospitals and other close-quartered populations. In 2005, there was a large outbreak of norovirus among Hurricane Katrina refugees housed in the Reliant stadium in Houston, Texas. The chef and restauranteur Heston Blumenthal knows the cruel fate of norovirus all too well. In 2009, his Fat Duck restaurant was forced to close in fear of the virus after 40 people complained of diarrhoea and vomiting.
If you are unfortunate enough to get struck down with norovirus gastroenteritis because you double-dipped the salsa at the office Christmas party, have no fear – despite there being no specific therapy, the usual symptomatic interventions will suffice. Oral rehydration, "feed a fever, starve a cold" and other mother-knows-best remedies will get you back on your feet. Although, once you have no more symptoms, you may still be infectious. Infected individuals may continue to "shed" norovirus up to eight weeks after symptoms subside.
If you're lucky enough, you can avoid it simply by being full of blood from a specific group. It seems human histo-blood group antigens may influence susceptibility to the virus. In a study by researchers at the Baylor College of Medicine, Houston, Texas, individuals with an O phenotype were more likely to be infected while those with a B and AB phenotype had decreased risk of infection and symptomatic disease. This revelation also mirrors findings in blood groups susceptibility to cholera.
So this winter, exercise good behaviour, wrap up warm and practise good hygiene (alcohol-based gels are useless as the virus is insensitive to alcohol, so stick to good old soap and water).
Avoid touching things. Fomite, a word recently made famous by Steven Soderbergh's film Contagion, refers to the inanimate objects of everyday life that can act as the transmission vehicle for such infectious organisms. So, avoid touching people, things, places, food and water. A list for your inner hypochondriac, long enough to send you into hibernation this winter.