The winter vomiting bug has been circulating throughout the Republic since early this year. Dr Muiris Houston, Medical Correspondent, explains.
Small round structured viruses or Norwalk-like virus (NLVs) are a recognised cause of gastroenteritis in both the community and institutions such as hospitals and nursing homes.
Despite being commonly referred to as the "winter vomiting virus", the bug has been circulating since early this year.
It first surfaced in a Co Louth hospital in January and has affected hospitals throughout the State, sometimes causing a severe interruption to routine services as is the case in Beaumont hospital, Dublin, at present.
NLVs are particularly resistant microbes and, unusually for a bug, which affects the gastrointestinal tract it is spread by both the airborne route as well as the more usual person-to-person contact. This is undoubtedly a factor in the spread of the illness through hospitals and hotels in the State.
Most people will be able to cope without medical help with what is a short but very sharp illness. The vomiting is severe - often projectile in nature - and the diarrhoea unpleasant, but most of those affected will be clear of symptoms in 48 to 72 hours. Other symptoms include abdominal pain and a low-grade fever.
For the elderly and those whose immune systems are compromised by other diseases, NLV can be more serious. While there is no specific treatment for the virus, these patients may require more intensive treatment in the form of intravenous fluids and special nursing. There have been no reported fatalities to date and the illness does not have long-term health effects.
The virus is known to cause in the region of one million cases of gastroenteritis in the UK each year, representing a recent rise of 60 per cent in the incidence of the disease.
Contaminated oysters and water have been identified as potential sources for the infection; however, because it is such a hardy virus, it is able to survive in the air and is usually transmitted from person to person.
There is a number of reasons for this year's prolonged outbreak: one is that NLV is not as common historically as other tummy bugs and so we have not had a chance to develop an immunity to the virus; secondly, viruses mutate rapidly and so it is virtually impossible to maintain immunity to these bugs, even for those previously infected, from year to year. And because NLV can be transmitted in the air as well as by the more usual hand-to-hand route, it is highly infectious.
Treatment consists of taking plenty of clear fluids. Antibiotics are not necessary and the disease is self-limiting without the need for specific medical treatment in the majority of cases.