dispatches from the frontlines of Shanghai medicine

Dr. Colin Walsh MB ChB MSc
New Pioneer
6407 3898

Influenza - More Than Just a Cold

An Underestimated Illness
Most people have experienced an attack of influenza but tend to forget how ill they felt at the time. The main symptoms of malaise, fever, aches and pains, headache, sore throat and cough caused by the flu virus commonly last about seven days, but it may take weeks to make a full recovery. Most people find they have to rest in bed or in a chair for several days and be off work for a week or longer. The cough may last up to three weeks (often longer in smokers). Attacks tend to happen in the winter. Healthy adults are unlikely to get serious complications such as pneumonia. Influenza is more of a danger for infants and the very old. In the United States influenza causes an average of around 20,000 deaths every year. As the virus is constantly changing (unlike cold viruses, which are stable) people have little or no immunity when a new strain of flu virus appears, even if they have had influenza several times before.

A Moving Target

Small changes in the virus occur almost every year, but at regular intervals there is a major mutational change and this causes a worldwide epidemic of influenza. These mutations may cause increased virulence and a large increase in flu-related deaths. During the past century we have been fortunate that only once did such a mutation produce a highly virulent killer strain. This happened in 1918 when there was a deadly pandemic that killed several million people worldwide - in the United States alone more than half a million people died. The unique feature of this epidemic was that many of those who died were healthy young adults. The strain of flu involved has not reappeared since then.

Influenza can be prevented. Safe and effective vaccines have been available for years and many large companies carry out annual mass immunization of employees in order to prevent disruption of their business from epidemics of flu. Most of the available vaccines are suitable for children and infants over 6 months old. The vaccines change each year to cover new strains of influenza as they appear. Annual immunization is strongly recommended for those of all ages with chronic respiratory disease (including asthma), chronic heart disease, kidney disease, diabetes, and anyone with an impaired immune system.

Amantadine can be used for the treatment or prevention of influenza in the above 'at risk' groups during epidemics, or for health care workers and other key personnel. Side effects can be a problem and so the drug is not recommended for everyone. Also it works for type A influenza but not types B or C, which limits its usefulness (though type C causes a milder illness than A or B).

Recently a new class of antiviral drugs has been developed which halts replication of types A and B of the influenza virus. Glaxo's Relenza, an inhaled powder, is already on the market and Tamiflu developed by Roche will be launched soon. These said to be effective if taken within the first 24 hours or so of the start of symptoms. Relanza got off to a poor start recently when the National Institute for Clinical Excellence (NICE) recommended that the drug not be made available on the NHS. The committee felt that the drug made too little impact on the illness to make its high cost worthwhile. However, Relanza does have a product licence and GPs can prescribe it - although the financial constraints under which they operate mean that they are unlikely to use it much.

These expensive new drugs need to be targeted properly, but unfortunately a confident diagnosis of influenza is impossible on symptoms alone. New diagnostic tests can give a result in 15 minutes. The new tests are Flu OIA (made by Biostar) and QuickVue Influenza Test (Quidel Corporation). Though progress is being made in the treatment of influenza, prevention is still better than a cure - and influenza vaccine is relatively cheap, effective and widely available.

New Pioneer has stocks of influenza vaccine at all its main centres. It is contraindicated in people who are allergic to eggs.