ATLANTA - Health officials warned today that West Nile virus, which has killed 18 people along the East Coast since it surfaced in the U-S three years ago, should continue its westward march this summer. <br>
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The Centers for Disease Control and Prevention said that inSouthern states, where balmy weather often stretches well into the fall, the virus is coming closer to year-round transmission. <br>
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Mosquitoes spread West Nile from infected birds to humans, who can then develop deadly encephalitis, or swelling of the brain. Humans cannot pass the virus to each other. <br>
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West Nile was first detected in New York in 1999. Last summer was the most severe so far, with 66 human infections and nine deaths reported. <br>
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Sporadic infections have been detected as far west as Illinois, Arkansas and Louisiana, and health officials say migratory birds will probably carry the virus even farther west this season. <br>
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No human cases have been identified so far in 2002.
