Medical Matters: After two years in which the number of people with mild influenza has been noticeably low, the National Disease Surveillance Centre has confirmed we are in the grip of a serious flu outbreak, writes Dr Muiris Houston.
It is also unusually early in the annual flu season, which runs from November to March, for the virus to have got a hold in the community. The earliest cases were picked up more than a month ago at a Dublin school.
Based partly on specimens from affected pupils, the National Virus Reference Laboratory has identified the strain of flu: A/Fujian/41/2002. So the virus is of the A type first identified a year ago in Europe. It then began to circulate in Australia and New Zealand during their winter, in July and August this year.
Of the three main types of flu, influenza A has always caused the greatest trouble. In different forms, it has been responsible for the world's greatest pandemics, including the infamous Spanish flu of 1918. The influenza virus can change its characteristics with relative ease. Minor changes in the surface of the virus, involving proteins called haemagglutinin (H) and neuraminidase (N), occur between each flu season. Referred to as antigenic drift, they are why it is necessary to reformulate the flu vaccine each year. Major alterations are referred to as antigenic shift. A completely new virus then emerges, along with the likelihood of an influenza pandemic. Luckily, such major changes rarely occur.
The Fujian-like flu causing the present illness is classified as an H3N2 strain. It is slightly different from the H3N2 Panama-like virus that is one of the components of the World Health Organisation-approved vaccine available from your GP. But because both have the same principal surface proteins, the Panama-like influenza A vaccine should help fight the sub-type circulating here.
Those for whom vaccination against flu is advised will therefore still benefit from the current vaccine. It should, at the very least, reduce the severity of the infection. Uptake among the over-65s, those with chronic heart and lung disease and people with diabetes is quite good. The Department of Health and Children is concerned, however, about a low uptake among healthcare workers. They are about 10 times more likely than the general population to contract flu. They may also infect older people and others for whom flu is potentially fatal.
For the majority of us without the vaccine, what can we do if the flu strikes? Probably most important is to take yourself out of circulation; this will be an easy decision for those with full-blown flu, as they will be unable to lift their heads from their pillows, so poleaxed will they feel. Plenty of fluid is important to counteract the initial high temperature. And paracetamol will help reduce severe aches and pains.
This is as much as can be done for the otherwise healthy person with influenza, certainly for the first five days or so. As long as your symptoms are beginning to ease by then, a visit to your doctor is probably unnecessary. In some circumstances help may be necessary, however.
If you are getting worse rather than better after a week, a visit to your family doctor is in order. If you develop unusual symptoms, such as coughing up blood or feeling a pain in part of your lungs, you should seek immediate medical advice.
Coughing up yellow or green phlegm suggests a secondary bacterial chest infection. Unlike flu, this requires antibiotics and is another reason to seek medical assistance. Children with flu have a higher risk of febrile convulsions because of the high temperature associated with infection. Such complications occur in one in five children hospitalised with flu.
Finally, a word of caution about paracetamol. Never exceed the dose indicated on the packet. Be vigilant about inadvertently taking additional paracetamol. Many preparatory flu remedies contain paracetamol as part of a cocktail of symptom-relieving drugs. It is quite easy to exceed the recommended daily dose of painkillers without meaning to. If you have taken paracetamol for 10 days in a row, then as a general rule it is advisable to contact your doctor before continuing for longer than this. There is some evidence that paracetamol residues accumulate in the liver. As the commonest cause of acute liver failure, paracetamol can be a dangerous drug. So be careful not to exceed the maximum daily dose - and, if in doubt, contact your doctor.
Let's hope most of us escape the flu this winter. It's a nasty infection that leaves victims below par for a good month after getting it. And if you are in one of the at-risk categories, it's not too late to be vaccinated.
You can e-mail Dr Muiris Houston at mhouston@irish-times.ie. He regrets he cannot answer individual queries.