Last Updated: 2003-05-15 10:00:34 -0400 (Reuters Health)

WASHINGTON (Reuters) - SARS may be scary, but for the United States and Canada West Nile virus promises to be more deadly, two experts predicted on Wednesday.

Severe acute respiratory syndrome has killed nearly 600 people and infected more than 7,500 in about 30 countries since it emerged in southern China in late November.

But only 23 of the deaths have been in Canada and none in the United States, said Dr. Paul Epstein of the Harvard Medical School Center for Health and the Global Environment.

"The attention focused in recent weeks on SARS is extraordinary and, it can be argued, excessive," Epstein said in a statement.

In contrast, he said, West Nile virus made 4,156 people ill and killed 284 in the United States and Canada last year.

West Nile appeared in the United States only in 1999. The virus lives in birds and other animals and can be transmitted by mosquitoes.

U.S. health officials say the disease now has a permanent home in the United States. Last year it spread to 44 states, Washington, D.C. and five Canadian provinces.

West Nile virus has spread to 230 species of animals, including 130 species of birds, said Douglas Causey of the Harvard University Museum of Comparative Zoology.

"Avian deaths from West Nile virus increased five-fold over 2001," Causey told a telephone briefing.

Epstein and Causey said drought in the U.S. and Canadian West could hasten the spread of the virus. During drought, water pooled in storm drains becomes concentrated and rich in the nutrients that nourish mosquito larvae.

Meantime, species that eat mosquitoes such as fish, dragonflies and frogs die out in drought.

Epstein and Causey blamed global warming for recent droughts.

"We know what the solutions are. We need better disease surveillance and defense systems," Causey said.

"We also need to change our direction in energy -- cutting far fewer trees, burning much less coal oil and gas that destabilize the climate and warm the globe," added Epstein.