The virus causing our latest flu outbreak was first identified several months ago in Johannesburg, says Liz Hunt
Last week, as increasing numbers became victims of the latest flu outbreak, the word "epidemic" was uttered for the first time. The word has fearful associations, calling to mind the Great Plague, disaster and sudden death. In fact, although it is too early to be certain, most experts think it unlikely that the current outbreak will reach epidemic proportions.

That may be scant consolation for the general public, however, as we sit at home, either nursing runny noses and chesty coughs or waiting for them to arrive.

Specialists are continuing their global quest to identify this year's virus. "We are always on the lookout for the one [strain] that is different, the one that fewer people will have some immunity to," says Professor John Oxford, of the Royal London Hospital, who is one of the country's leading virologists.

The virus that is now being isolated with some regularity from flu victims is the A/Johannesburg/Strain, first identified in Johannesburg, South Africa, last year. Exactly what route this A/Johannesburg/ Strain took from its origin, possibly somewhere in southern Africa, through the southern hemisphere during the winter period there, is difficult to establish, according to Karin Esteves of the Division of Emerging Communicable Diseases at the World Health Organisation in Geneva.

"There were cases reported throughout southern Africa and New Zealand initially, and since then it has been isolated in Australia, Singapore, Thailand and Hong Kong," says Ms Esteves. "In South America, we have recorded isolates in Brazil and Chile."

Every spring, a team of virologists and public health officials meet at WHO's headquarters in Geneva to agree the cocktail of influenza strains to be included in the vaccine, which is changed every year. "Acting on the basis of the early reports of A/Johannesburg/Strain, the world's flu watchers decided that it was a must for inclusion in the 1995-96 influenza vaccine," says Ms Esteves. This year's combination also includes A/Singapore/Strain - responsible for an outbreak in 1987 after the flu watchers failed to spot its potential for havoc - and B/Beijing/Strain.

So far the virologists have been proved right in their isolation of the A/Johannesburg/Strain. During the autumn and early winter, it has claimed victims throughout western Europe, including Scandinavia. Here in Britain, WHO says A/Johannesburg/Strain appears to have hit Scotland hardest first, although RCOGP figures now show that central and southern England have borne the brunt of illness so far.

As the flu season develops and more data is gathered by epidemiologists, it may be possible to track the spread of A/Johannesburg with greater accuracy, according to Professor Oxford, and even determine where the first cases ocurred in the northern hemisphere. In November/December of 1993, there was a mini-epidemic of influenza, nicknamed by virologists as the "showboat flu". This was because the first case was linked to a passenger on a showboat on the Mississippi River who fell ill in August that year.

Tomorrow: Consuming, page 11, looks at treatments on offer for flu and the common cold.