Alabama confirmed its first case of the West Nile virus this year on Wednesday in a 71-year-old man. Also, state health officials in Illinois and Florida said Tuesday they detected the first human cases of the disease this year.
Across the nation, over 100 have been diagnosed with the disease this year and five have died in Louisiana, bringing the state total 72. The virus has been detected in birds and people in 34 states and Washington, D.C. health officials expect it will continue spreading west.
The number of cases in Texas is up to 11, Mississippi has confirmed 22 human cases of West Nile, and Arkansas, Illinois and Washington State have recorded one case each.
As CBS News Correspondent Bob McNamara reports, it is Louisiana that is feeling the brunt of the epidemic, the worst outbreak in U.S. history.
Louisiana health officials predicted the West Nile virus epidemic would worsen, and it has. Louisiana Gov. Mike Foster has declared a state of emergency and is asking federal officials for money to beef up mosquito-killing efforts.
For the first time, a horse has been identified as having contracted the virus. The owner of the Ohio animal reportedly noticed a lameness in the horse's rear leg.
Health officials say a virus vaccine may be years away.
"Five to 10 years, if ever," said Dr. Roy Campbell, of the Centers for Disease Control. "It takes a long time to get a vaccine."
Mosquitoes transmit the illness from infected birds to people. Most people bitten by an infected mosquito will show no ill effects, some will show flu-like symptoms, a few can develop potentially fatal encephalitis.
Meanwhile, more than half a dozen states worried about West Nile virus are using climate-based computer models to predict the course of the mosquito-borne disease before a fatal outbreak occurs.
Public health officials usually rely on reports of dead birds as an early warning sign that West Nile is spreading in their region. Scientists say this new method would warn local officials in advance if their counties are at high risk for the virus.
"We look at this as another tool we can potentially use to help us as we try to protect people from catching West Nile," said Bryon Backenson, assistant director of the New York State Health Department's arthropod-borne disease program.
Last year, the state collaborated with NASA and Oxford University to create climate maps based on satellite data to track the virus. Delaware, Florida, Louisiana, Maryland, South Carolina and Virginia have since joined.
In the $504,000 NASA-funded project, state health departments tally the number of dead birds and mosquitoes that test positive for West Nile while NASA satellites pick up weather information like temperature and humidity.
The information is sent to Oxford, which uses a computer program to create "risk maps" showing areas infected with the virus, temperature and vegetable distribution and migratory routes of birds.
State health officials, in turn, will use the maps to warn counties when they are at high risk for West Nile so they can develop a plan to fight mosquitoes and the virus.
"Risk maps will help authorities take charge and control as well as anticipate the disease," said Oxford ecologist David Rogers, who helped create the maps.
Health officials stress that the disease is relatively easy to prevent.
"It's not time for panic," said Dr. Roy Campbell, a Centers for Disease Control and Prevention epidemiologist heading up a team researching the virus in Louisiana. "It's time to take precaution."
That's the theme of a $200,000 multimedia "Fight the Bite" campaign in Louisiana, including television spots in which Gov. Foster repeats oft-heard advice: use mosquito repellent, get rid of standing water, stay indoors at dusk and dawn or wear long clothing when going out at those heavy-mosquito hours.