Part of the challenge of treating West Nile virus is the unpredictability of outbreaks.
Certain factors could help guide future prevention of the mosquito- borne illness.
"There were certain, what we call, geographic hot spots, the same geographic areas within our county tended to be affected more heavily during an outbreak," said Wendy Chung, MD, Dallas County Health and Human Services in Dallas, Texas.
Texas has seen some of the largest outbreaks in the country.
Researchers there are studying weather patterns, timing and geography to determine which areas are most prone to cases.