MEDICAL MATTERSDriving along with little or no traffic about, it was one of those pleasant winter Sunday mornings. The trees and fields glistened in the low winter sunshine; all was well with the world, writes Dr Muiris Houston
That is until the initial unsettled feeling in may stomach started. No pain, but a rising sense of nausea. What had I eaten yesterday? Nothing out of the ordinary; we had dinner with friends on the Saturday night which, due to our hostesses' superlative cooking skill, had gone down a treat.
By the time I arrived home 40 minutes later, the nausea was full blown. Now, it was at a level where it is not a question of if, but rather when, you will vomit.
As it happened, however, the diarrhoea started first. With little warning the first of the explosive watery diarrhoea entered the toilet bowl. Soon afterwards, the retching started. The rest of the Sunday took on a less pleasant outlook.
In the best traditions of "physician heal thyself", I tried to ameliorate the symptoms of the now obvious gastroenteritis.
At the same time the medical detective in me tried to figure out what the cause might be. A quick check with our friends confirmed that no one else had been affected, which put food poisoning down the list of possibilities. That and the fact that by Sunday evening I was shivering and had developed a headache and muscle pains.
Viruses are the commonest cause of acute gastroenteritis. With the more generalised flu-like symptoms now superimposed on the diarrhoea and vomiting, a bug was the most likely source of my discomfort.
Then the penny finally dropped; one of the dinner guests, a woman sitting next to me, had been telling us how her "acid reflux" was bothering her. Some way through the meal, she had disappeared for almost 10 minutes, before returning and whispering her apologies to the effect that the "acid" was so bad it had caused her to vomit.
Between the whispering in my ear and a subsequent goodnight peck on the cheek, I had obviously shared enough airspace with the real cause of her discomfort - a virus - for it to have entered my system.
And there is only one gastric virus that likes to enter the body by inhalation rather than by the faecal or oral route - the Norwalk virus, commonly known as the winter vomiting virus.
Also known as the small round structured virus (SRSV), the Norwalk virus was first identified after a 1968 outbreak of gastroenteritis at a school in Norwalk, Ohio.
According to the US Centre for Disease Control and Prevention, it causes about 23 million cases of acute gastroenteritis in the US every year.
The winter vomiting virus is actually something of a misnomer. It occurs year round and had been the source of repeated outbreaks of gastroenteritis on cruise ships in 2002.
Here, it regularly causes the closure of hospital wards as management try to contain its spread among already sick patients. Infants, older people and those with weakened immune systems are less able to cope with the frequent vomiting and diarrhoea that typically last for 48 hours.
The incubation period of the Norwalk virus is 12-48 hours after infection. The vomiting is both copious and projectile and diarrhoea is watery; both last for up to two days. Abdominal cramps, headache, fever and a general feeling of malaise complete the unpleasant set of symptoms.
The classic method of person-to-person spread is by droplets generated by the projectile vomiting. There is no cure or treatment for the bug. All you can do is lie low, take plenty of fluids and wait for your immune system to overcome the infection. If possible, you should avoid close contact with other people for at least 72 hours.
Certainly, it is not a good idea to visit hospitals or nursing homes for at least four days after your symptoms have settled. As I write, there are over 150 cases of Norwalk virus in hospitals in the Republic. St Vincent's Hospital, Dublin, had 15 wards closed with 76 patients and 43 staff affected by the bug, as of last Friday. When a hospital is affected like this, it stops elective admissions and puts serious back-pressure on the accident and emergency department.
Last week, it was announced that the Norwalk virus had been grown for the first time in a laboratory.
Scientists at the Washington University School of Medicine in St Louis said the technique may lead to the development of a vaccine for the infectious disease.
"By looking at the virus we've grown in the lab, we were able to identify a part of the capsid, the virus's protein shell, that is essential to the ability to cause disease," Prof Herbert Virgin, professor of pathology and immunology, said. Altering or disabling the virus capsid could be a route to developing a workable vaccine in humans.
Meanwhile, I am back at work. A few pounds lighter and with my appetite yet to recover its full vigour, I should have enough antibodies in my system to ward off the Norwalk virus for the next few months at least.
Dr Muiris Houston is pleased to hear from readers at mhouston@irish-times.ie but regrets he cannot answer individual queries.