Panic in Central Park

New York is in the grip of the jitters. For once, it is not the summer heat pushing it over the edge - temperatures this summer have been unusually kind - nor has there been a new surge in violent crime. So why, then, is everyone so afraid that Central Park was sealed shut on Monday evening, mothers are keeping their children indoors, and overnight camping expeditions for inner-city kids are being cancelled?

New York is in the grip of the jitters. For once, it is not the summer heat pushing it over the edge - temperatures this summer have been unusually kind - nor has there been a new surge in violent crime. So why, then, is everyone so afraid that Central Park was sealed shut on Monday evening, mothers are keeping their children indoors, and overnight camping expeditions for inner-city kids are being cancelled?

They are afraid because of an invisible enemy that has been circling the city for months but now, suddenly, appears to be closing in. It sounds like the script to one of those sci-fi films about aliens abducting humans from the skyscrapers of Manhattan, but this menace is far from fictional. It is a mosquito-borne disease with a scary-sounding name, the West Nile Virus. Catch it and you may develop forms of encephalitis or meningitis. If you are old, infirm or very young, there is a chance you will die.

At least this time the city is more or less prepared, unlike last summer, when West Nile Virus appeared for the first time. Never before detected in the western hemisphere, it prompted near panic in New York. A massive pesticide spraying campaign was set in motion. Helicopters doused the entire metropolitan area with a chemical called malathion, considered carcinogenic by some scientists. Once autumn came and the mosquitoes vanished, seven people had died, and symptoms, which include swelling of the brain, had been found in 62 others.

The outbreak, however, had left many questions unanswered. How had a disease previously confined to eastern Africa, parts of the Middle East and southern Europe - it was first detected by virologists working in the northern province of West Nile in Uganda in 1937 - made it over here? Some observers even asked if it had been introduced to the city by bio-terrorists. More likely, we now know, it arrived by freighter, along with a cargo of exotic birds for American collectors.

More urgent, however, in the minds of most New Yorkers, was this: how had their carefully controlled environment of concrete, air-conditioning and hermetically sealed foods been invaded in this way? This is a metropolis of humans, run by humans. We don't have snakes here. Or malaria, earthquakes or volcanoes; nothing like that. The fact this disease was called West Nile and came from Africa seemed even more ludicrous. Africa? Where is that exactly?

What the leaders of the city did understand was that there was every chance the virus would be back this year. Infected mosquitoes pass the virus to their eggs. Come the spring, the eggs would hatch - and the virus would be out there all over again. Thus a new plan of action was developed to keep it at bay. Gallons of larvacide were poured down drains. Larva-eating fish were purchased in bulk and introduced to city reservoirs. Chickens were bought and deployed around the city as sentinels for any new onset of the virus - every week the chickens have blood drawn for tests. While mosquitoes are the host and can pass the virus to humans, birds are also carriers.

Meanwhile, battle plans were drawn up for spraying once more. At the urging of federal environmental agencies, Mayor Rudy Giuliani ordered that as far as possible the spraying should be done from the ground this year instead of from helicopters. Moreover, the use of malathion was scrapped in favour of two slightly less toxic substances, brand-named Anvil and Scourge. Their main active ingredient is sumithrin, a natural pesticide produced in nature by chrysanthemums.

In the end, the chickens weren't much help. Dead crows, including a few in Staten Island, the southernmost borough of New York, did that job. Found a few weeks ago, they tested positive for the virus and the alarm was sounded. Soon afterwards, city detection teams found infected mosquitoes in a handful of the some 120 traps that were placed all across the metropolitan area this spring. Spraying from pick-up trucks was initiated in Staten Island and in some of the city's suburbs last week.

Then came news on Monday that a trap near the southern edge of Central Park had also come up with some infected skeeters. Calling an immediate press conference, Mayor Giuliani had the air of a leader about to go to war. Grim faced, he presented journalists with maps and diagrams. He had two messages: don't panic, but this is serious. While, as of yesterday, no cases of West Nile had yet been detected in any humans, this was the first time infected bugs had been found in Manhattan itself.

Giuliani is caught between several forces. If the worst happens and the numbers of the deaths from West Nile equal or even outstrip those of last summer, the political punishment for him could be dramatic. But he is bound also to be accused of having overreacted when he ordered Central Park closed on Monday evening to allow crews to spray its entirety. He managed to wreck the night for some 30,000 music lovers who had already come to the Park for an annual open-air concert by the New York Philharmonic Orchestra. But the Mayor was unapologetic. "Having 30,000 people there really would have been risking the odds," he said.

Nor is the Central Park spraying the end of it. Yesterday evening, weather permitting, a fleet of pick-up trucks loaded with large tanks of the pesticides was due to cover every square foot of Manhattan, river to river, from 23rd St all the way up to 110th. All this sounds extreme when you consider that, according to some experts, you have only a one-in-300,000 chance of catching West Nile even if you are in the epicentre of an outbreak. Critics of Giuliani noted this week that 2,600 people died of the flu in New York last year, and yet he has not ordered an obligatory programme of flu shots.

Angriest of all, however, are several environmental and health groups who argue that the risks associated with West Nile are far outweighed by the dangers of dousing a city as densely populated as this one. (As the trucks prepared to pass through Manhattan last night, all residents were warned to keep themselves and their pets indoors, close windows and turn off air- conditioning). Even if there is no carcinogenic risk from these, less potent, pesticides, most health experts concur that they can choke asthmatics and the very old and cause skin problems.

"This city is proceeding with this irresponsible course of action without fully weighing the risks," complained Kimberly Flynn, a researcher for the New York Environmental Law and Justice Project, one of several groups suing to have the spraying stopped. Doubts were also expressed by Dr Cheryl Frydman, an assistant professor at Mount Sinai Hospital. "My concern is - especially if you have young children, developing neurologically - if it's on the picnic table, what should you do the next day after spraying? It doesn't seem like a chemical that you have to be hysterical over, but it's a chemical and it hangs around."

New Yorkers, in fact, are not prone to outright panic. When the police fanned out to evacuate Central Park, there was no stampede for the exits. And by Tuesday morning folk were back within its boundaries, perhaps in slightly reduced numbers, to indulge their start-the-day rituals - scooping up their dog's gifts to the turf, in-line skating to work or taking a stroll. The Philharmonic played its cancelled concert last night.

Without question, however, there is unease in Gotham now. Yesterday in a train, I heard a fellow passenger blurt, "Look, there, is that a mosquito? Is that a mosquito?" It was just a fly, but the collective blood pressure in our carriage had shot up a mile.