Real 'flu not to be sneezed at

People talk about getting a "touch" of 'flu but a touch of the real thing is like a "tap" with a sledge hammer. There is no mistaking an encounter with the influenza virus, says Dr Alan Shattock, a senior lecturer in medical microbiology at University College, Dublin. "With a genuine 'flu you are simply too weak to stay active. A real 'flu will hit you very suddenly. Within an hour or two you will feel dizzy, have a headache and often sever back pain."

Most of those complaining of 'flu are experiencing a common cold and true 'flu doesn't usually appear here until after the influx of holiday visitors and those home for Christmas. The Virus Reference Laboratory at UCD had not isolated any influenza up to late last week.

"It is spread around the world by people travelling. When a new strain breaks out, traditionally in the Far East, it spreads from east to west." It arrives here with the Christmas rush.

Our too-familiar use of this illness's name belies the dangers posed by a 'flu outbreak. The Spanish 'flu of 1918 killed over 20 million people worldwide. There were also many deaths, particularly among the very old and very young, when the Asian 'flu came to call in 1957, and the Hong Kong in 1968.

The punch delivered by a 'flu depends on how much exposure we have had to it. If it has passed through before then many people will be immune to it. The World Health Organisation monitors the strains of 'flu moving around the world so vaccines can be provided ahead of time for those who most need them. There are periodic small changes in 'flu types, known as antigenic drift, but there can also be major mutations to wholly new forms, known as antigenic shift.

The viral types are described by specifying the type of proteins found in the "coat" which surrounds the virus, haemagglutinins and neuraminidase. Recent 'flus have thus been coded as H3N2 and H2N2, familiar strains for which there are vaccines.

"If one of the proteins changes you will get an epidemic. If they both change you will get a pandemic," explained Dr Shattock.

Influenza specialists worldwide are nervously watching developments in the Far East, however, where a wholly new form, H5N1 and dubbed the "bird 'flu", has appeared. In common with most 'flu types, H5N1 mutated from an avian form, crossing the species barrier to affect humans.

This form killed a three-year-old boy in Hong Kong last May and there was a long gap before any other cases were reported, leading specialists to believe H5N1 was not very infective.

Now they are not so sure. There have been 11 more suspected or confirmed cases of H5N1 and a man of 54 and a woman of 60 have died after contracting it. There are real fears that the new form could cause a worldwide pandemic, with no vaccine available to protect those at greatest risk. While some specialists believe it is just a matter of time before H5N1 sparks worldwide illness, others argue that it might have low infectivity because there have been so few cases detected in Hong Kong since last May.