The tiny highly contagious norovirus is beginning to wreak havoc again as Wexford General Hospital succumbs to its germs. Claire O'Connellreports
Last week Wexford General Hospital closed its doors to visitors. The culprit? The tiny but highly contagious norovirus or winter vomiting bug.
It wreaks annual havoc on hospitals around Ireland, where high bed occupancy rates do little to help contain the spread of the virus.
Norovirus infects an estimated 1-5 per cent of the population each winter, according to Dr Paul McKeown, a consultant in public health and medicine with the Health Protection Surveillance Centre (HPSC).
So far, this winter has been relatively quiet, with around five-eight outbreaks recorded per month across the State, according to provisional HPSC figures, although McKeown notes that official notifications are probably a "gross underestimate" of actual numbers.
"In general it has been pretty uniform across the country," he says, adding that the HPSC monitors norovirus outbreaks at home and abroad. "Things are becoming busy, but we don't know yet if this is a blip or an upsurge. We are just saying to be prepared."
When the virus strikes, symptoms such as vomiting and diarrhoea can come on suddenly. And while for most people, the illness merely means an unpleasant couple of days, for the very young or elderly or for those with pre-existing conditions, dehydration can potentially cause additional problems.
Hospitals are particularly vulnerable to norovirus infections and host around 40 per cent of recorded outbreaks, explains McKeown.
"There's a common misperception that this means places are dirty. What it means is it's an extremely infectious bug and it concentrates where people are concentrated," he says.
"Where people are in closer congregation it's much more likely to spread. Hospitals are particularly prone to it."
Official diagnosis of norovirus from stool samples can take around two-four days, so hospitals also watch for familiar patterns of infection to identify potential outbreaks as early as possible, says consultant microbiologist Martin Cormican, professor of medical microbiology at NUI Galway.
"If a group of patients develops projectile vomiting or diarrhoeal disease without another, obvious explanation, then that's usually a signal.
"Probably most of the hospitals in the country have been through this so many times, you get this sinking feeling of 'here we go again'."
The virus can spread through the air, but the main route of infection is via contaminated surfaces such as hands and food. In addition, an infected person may spread the virus even before they know they have it.
"You are shedding virus before you feel unwell at all, and you continue to shed the virus after you get better," says Cormican, who adds that following an episode of vomiting or diarrhoea, the virus can persist in the environment for days and possibly weeks.
Rigorous cleaning of infected surfaces is central to managing an outbreak, and limiting entry of the virus into hospitals is also important. Norovirus circulates in the community each winter, and employees, patients and visitors can bring it into the hospital setting.
"One of the things you can do to close off those avenues of introduction is to try to get people to be more reasonable about visiting," says Cormican.
Closing wards to visitors can protect patients, staff and visitors themselves from the misery of the condition and gives the staff more space and time to deal with the crisis, he adds.
"We want the staff to be looking after the patients and paying as much attention as they can to strengthening infection-control practice."
Cormican notes that to prevent and contain outbreaks, patients with suspected norovirus should be isolated, but high bed occupancy rates in Ireland pose a problem.
"Most of the beds are full most of the time in most of the hospitals, and when you have an acute problem with norovirus, trying to cohort people and contain the spread of the infection is a lot more difficult.
"It's really very challenging, because you are trying to balance the control of the outbreak with trying to ensure that the service continues to run."
At the moment there are no drugs to kill the winter vomiting bug and the virus changes slightly every few years, which makes it difficult to develop a vaccine, explains Cormican. "As far as I'm aware there's no immediate prospect of a norovirus vaccine, so for some time to come we are going to be looking at infection control and limiting the damage," he says.