"There are lots of reasons why people should be interested in mosquitoes," said Spielman. "Now, perhaps there is some fear about them, but in this book I try to help allay those fears or at least put them in a context that makes those fears reasonable."

The West Nile encephalitis outbreak prompted Spielman to write the book with Pulitzer-Prize winning author Michael D’Antonio. Spielman said he was "amazed" when he heard two years ago that West Nile encephalitis, mainly a disease of the Middle East, Africa, and parts of Eastern Europe, had been found in a large American city.

For him, the questions came immediately and remain unanswered: How did the virus get here? How many people will become infected? How many will die?

"The advent of West Nile encephalitis in the US is an event that has changed urban life," said Spielman. "From now on, we will always wonder whether the mosquito that we hear flying around our ears at 2 a.m. is one that carries the virus."

Still, Spielman pointed out, West Nile encephalitis is not as nasty as other mosquito-borne viruses. While everyone should take precautions to avoid mosquito bites, he said, many people infected with West Nile virus have minor or no symptoms. Elderly people are most at risk while small children are more likely to become ill than healthy adults. In total, eight deaths from West Nile encephalitis were confirmed by the Centers for Disease Control and Prevention (CDC) in 1999 and 2000. None have been reported so far in 2001.

Those numbers are nothing compared to the number of people felled by other mosquito-borne illnesses described by Spielman and D’Antonio. In 1793, 5,500 Philadelphians died from yellow fever, a virus transmitted between humans by mosquitoes. In this case, the mosquitoes were carried to the US from a West Indies ship that had berthed in the city’s port. Panicked by the high death rate, Philadelphians still healthy enough to run fled by the thousands.

The yellow fever pathogen causes liver failure, creating a yellow hue to the skin, and internal hemorrhaging. Blood flows from the mouth and nose.

Thousands of workers died from yellow fever and malaria while constructing the Panama Canal in the late 1800s. An ancient illness caused by parasites and carried by mosquitoes, malaria has killed countless people worldwide and continues to wreak havoc today, particularly in Africa. More than two million people are expected to die from malaria around the world this year alone.

In the mid-1950s, six people died of Eastern Equine encephalitis in Massachusetts–not a particularly startling number, but the disease has a phenomenally high mortality rate, killing about half of its victims. Further spread was stymied by insecticide spraying, surveillance, and the habits of the mosquitoes that carry the virus–they tend to live in remote areas among white cedar trees.

In his book, Spielman clearly revels in the many facets of mosquitoes beyond their capability to carry disease. The insects are pure pests, benefiting nothing other than the pathogens they carry.

Yet, with more than 3,000 species in their family, mosquitoes are among the most varied animals on the planet, found in every climate, from the wind-swept, frozen Arctic tundra to the humid jungles of the Amazon.

Not all mosquitoes, not even all female mosquitoes, drink blood. One species relies solely on the nutrients in water that collects in the leaves of pitcher plants. Another swoops in on obliging ants, sticks its proboscis down the ants’ throats, stimulates the ants to regurgitate, and sucks up the resulting food.

Mating, too, varies among species. Some form huge swarms above the treetops, creating a buzzing, dusky cloud. In one particularly rapacious species, the males typically impregnate females as the females emerge helplessly from their pupal casings; the females fly away, minutes old and impregnated.

Spielman said to expect more outbreaks of mosquito-borne diseases in the future. "The issue of mosquitoes is now extremely important with West Nile encephalitis in the United States and the resurgence of malaria and other mosquito-borne diseases in other parts of the world," he said. "We will continue to study this fascinating little creature."

Mosquito: A Natural History of Man’s Most Persistent and Deadly Foe is published by Hyperion and will be available in bookstores on June 13.

Related Site:

HSPH Research : Mosquito-borne Viruses -- Includes information on mosquito-borne viruses and West Nile encephalitis.