Health officials in St. Louis and Houston are awaiting confirmation from the Centers for Disease Control that a woman from each city has died after being infected with West Nile virus.
If confirmed, the 75-year-old St. Louis woman will be the first death in Missouri since the virus first appeared last year. She died Aug. 7.
The also-unidentified Houston woman was hospitalized on Aug. 8 and died on Friday, said Kathy Barton, spokeswoman for the Houston Department of Health and Human Services. If confirmed, she will be Texas' first West Nile death this year.
"There was going to be a death in the state," Barton said. "We are not surprised to have had a death."
Texas Department of Health officials say the state has had 25 cases, 13 of which are in Harris County.
Five Missourians — all in the St. Louis area — have tested positive for the mosquito-borne West Nile virus this year. Also last week, state health officials announced that a Massachusetts resident had contracted the virus while visiting St. Louis in late July.
St. Louis Health Department chief Mike Thomas said one or two of the other Missourians were still hospitalized. The others have been released from the hospital.
Horses are being tested in Colorado for West Nile virus after the animals showed symptoms of the disease over the weekend. Five other horses and one crow have already been confirmed to have the mosquito-borne disease.
Symptoms of the disease in horses include elevated temperature, stumbling, lack of coordination, weakness of limbs and partial paralysis. One in three horses who get the disease will die.
And in Wisconsin, a Green Bay zoo is taking precautions to protect its valuable bird collection from the possibility of the West Nile virus.
The NEW Zoo keeps fresh water running into most ponds to protect the birds from mosquitoes. Penguins are brought in at night, and during the day sprinkler systems are turned on to keep the insects away.
Zoo director Neil Anderson says the zoo has a collection of more than 100 birds, some endangered species valued at $100,000.
St. Louis officials have stepped up mosquito-fighting efforts. Health officials say residents should also take precautions — wearing insect repellant during early-morning and early-evening hours, keeping yards free of standing water to limit mosquito breeding areas.
But Thomas cautioned against overreacting.
"Most of the people who come down with the virus don't even know they're infected," Thomas said.
Prior to the woman's death, 11 people had died from the virus in the U.S. this year.
A CDC expert, Dr. Lyle Petersen, has said the disease's peak this year may not come for several weeks and could infect hundreds more people.
So far, the virus has been found in every state east of the Rocky Mountains, with human cases confirmed in nine states and the District of Columbia. As of Saturday, the CDC listed 251 human cases in the country this year.
Through late last week, state health officials had confirmed that more than 100 Missourians had been tested for the virus. The state agency reported 89 cases of birds killed by the West Nile virus in 28 counties and the city of St. Louis, and 29 cases of horses infected with the virus in 16 counties. Some of those horses also have died.
West Nile first appeared in the United States in 1999, when seven people infected with the virus in New York died.
Symptoms of the West Nile virus are often similar to the flu. But in rare cases, the virus can cause encephalitis — a swelling of the brain that can be fatal.