Trundling through the suburban streets of the Bronx last week, the truck looked like any other New York city council vehicle. Only the fine spray pouring from the back gave a clue to its real purpose: saving lives.
It was on the track of the killer West Nile virus, an infection that first appeared in the US four years ago and will this year spread to the entire country. Experts are predicting that 2003 will see the worst-ever American outbreak of the disease, which is carried by mosquitoes.
New York has begun preparing for the worst. Squads of vans have sprayed the city's outskirts to kill the insects and destroy any larvae they may have laid in the swampy land around the metropolis. The trucks work through the night and people with respiratory problems have been warned to stay indoors as they pass.
Last year the virus appeared in 44 states, infected 4,156 people and killed almost 284. This year, as the peak season begins, the signs are not encouraging. Experts at the Centres for Disease Control believe the disease is being detected at three times the rate of last year. It has been found in states where it did not appear last year and there have been 446 cases and 10 deaths. 'We could be in for a very serious affliction this summer,' said CDC director Julie Gerberding.
Experts warn that the disease is spreading so fast and adapting so well to local conditions that it may become present 12 months a year in some areas.
The disease is usually harmless to humans and goes unnoticed. But in some cases, especially among the elderly, it can trigger a serious reaction, leading to coma and death, caused by a rapid swelling of the brain. There is no treatment - a vaccine is believed to be at least a decade away.
Another killer virus, Eastern Equine Encephalitis, is adding to the threat. Usually there are fewer than five cases a year in the US, but this year there have already been seven. While West Nile kills about 15 per cent of those who fall seriously ill, EEE has a fatality rate of up to 70 per cent.
The epidemic is being caused by unusually warm and wet weather on the East Coast that has seen mosquitoes breeding in huge numbers. It has even spurred some calls to bring back mass spraying with DDT, which helped to eradicate malaria-carrying mosquitoes in America in the 1970s.
Many say that current official advice - to use mild sprays and encourage people in infected areas to slather on insect repellent - is not enough. However, environmental concerns about the effect of DDT and fears that it carries a cancer risk - the chemical is banned in Britain - has made its use politically difficult. The CDC said it would be up to local communities to make the decision depending on how serious the West Nile threat was in their area.
