Norovirus

Norovirus is actually a collection of similar Small Round Structured Viruses (SRSVs) and was known as ‘gastric flu’ for years until the eponymous causative agent was isolated after an outbreak in Norwalk, Ohio. Advances in DNA analysis then showed that Toronto virus, Mexico virus, Hawaii virus and Snow Mountain virus were all from the same family of Calciviridae.]

There are several key differences between influenza virus and Norovirus:

  • Norovirus is generally transmitted via the faeco-oral route and not by sneeze droplets
  • Carriers can be asymptomatic and still infectious
  • The “48hrs symptom free and you are safe to return to work” etc rule is nonsense – having recovered you may still be stool positive for up to a fortnight
  • Normal cleaning products and protocols do not kill Norovirus – including bleach, disinfectants, alcohol gels etc

Referring to The Telegraph (29/03/10)

Record numbers hit by Norovirus – Record numbers of people are falling ill with the winter vomiting bug, official figures show.

Cases of norovirus are significantly higher than normal for the time of year – with the unusually cold weather and a highly infectious strain to blame.

Since Christmas, the rate of new cases has far outstripped that seen two years ago, described by experts as the worst outbreak ever seen. Experts believe the coldest winter for 30 years has encouraged people to spend more time indoors, where the bug is spread more readily to others. In parts of the country, hospital wards and schools have even been forced to close in a bid to contain the outbreak.

Family doctors are also warning that they are seeing large numbers of patients with symptoms of the bug, with some contagious strains believed to be circulating. Although not dangerous for most healthy people, the infection usually results in two to three days of violent vomiting and extended periods away from work. In the case of young children and the elderly it can cause them to become dangerously dehydrated and even die.

According to the HPA, the number of laboratory confirmed cases during the past eight months is now higher than during the winter of 2007/2008, which at that stage was the worst on record.

This month a primary school, the Willows in Newbury in Berkshire, was forced to close for two days after 67 pupils, almost a third of the entire school roll, showed symptoms of the bug.

Norovirus outbreaks have also caused the closure of 152 hospital wards across England in recent weeks.

Some hospitals have had to close more than one ward in a bid to control the infection.  First Care, the absence management group who monitor more than 100,000 staff across Britain, said since February sickness levels from the illness had been above that of last year.

There was also a significant increase in mid-March when there 23 per cent more people off sick with norovirus than earlier in the month, their database shows.

Those with the infection are warned to drink plenty of fluids and practise good hygiene to avoid spreading the virus to others.

Although the infection rate has fallen since its peak earlier in the winter, it is still around 50 per cent higher than at the same time last year, with around 500 new laboratory confirmed cases a week earlier this month.

The figures show that in total, there were 7,302 confirmed cases of norovirus between July and the end of February this year – higher than during the same period last year, when there were 5,976.

The figure is already higher than the whole of 2007/08 when there were 6,009. The HPA collects figures on the vomiting bug from July to the following June – so that it can include the whole of a winter season in one year’s figures. For every confirmed laboratory case of the virus it is thought that there are hundreds more in the community.

In total, the HPA estimat