NEW YORK (Reuters) - New York City on Monday will launch a major assault on the West Nile virus in an attempt to stop a second U.S. outbreak of the mosquito-born, brain-swelling disease that killed seven people last summer.

In a statement released on Thursday, the city's health department said it will only spray insecticides as a last resort, and omitted malathion from the list of insecticides it will use to fight the disease, carried by birds and spread by mosquito bites.

In the summber of 1999 seven people died and more than 60 became infected by the virus, which can cause lethal brain diseases like encephalitis or meningitis. The virus, more commonly seen in Africa and Asia, was unknown in the Americas before the 1999 outbreak.

Environmentalists, community activists and many residents fear a repeat of the 1999 widespread aerial and ground spraying of malathion that took place in the city and its suburbs.

Experts have described malathion as being relatively harmless to humans, but it can metabolize in the body to maloxin, a toxin that causes effects similar to nerve agents.

The city plans an aggressive campaign that begins on Monday to help prevent mosquito larvae from maturing into adults. The plan includes larviciding, mosquito, bird and human surveillance activities, and a public education campaign.

``Our expectation is that, with an early and aggressive campaign against mosquitoes that includes the city's larviciding efforts and the public's contributions through eliminating areas of standing water where mosquitoes can breed, the need to spray adult mosquitoes will be greatly reduced,'' New York City Health Commissioner Neal Cohen said in a statement released Thursday.

The health department said that if spraying is needed, it will use resmethrin, sumethrin and permethrin. They would be sprayed by truck at first, but also by air, if necessary.

The city also said it will step up the use of a larvae-eating fish, Gambusia affinis or ``mosquito fish,'' in waste water treatment plants where it finds evidence of mosquito larvae.

In March the Centers for Disease Control said traces of the West Nile encephalitis virus were found in mosquitoes wintering in the New York area, confirming fears the city again would have to battle the disease.

On Thursday Secretary of Health and Human Services Donna Shalala said she had appointed a national coordinator to oversee the campaign against the virus. It is not known how the virus got to the United States.