OKLAHOMA CITY (AP) — The number of human cases of West Nile Virus has leveled off in Oklahoma, a state health official said Thursday, while the number of horses with the potentially deadly virus has risen sharply in the past two months.
The state has had a record 176 cases and 12 deaths due to the disease thus far in 2012, said state epidemiologist Dr. Kristy Bradley. That includes six cases and one death in the past two weeks.
Even as the virus is waning in the human population, the number of horses that have contracted the disease has jumped from two at the end August to 39, with 14 cases in September and 23 in October, according to state veterinarian Dr. Rod Hall.
Bradley said the threat to humans has not disappeared. And she warned that several continuous days of 70 to 80 degree temperatures, which the state has had this week, could bring the Culex mosquito back out.
“We won't say it's completely over until there are no mosquitoes flying and biting, but certainly the risk has decreased significantly as we get further and further into fall,” Bradley said. “The primary reason is the Culex mosquito is entering into hibernation. During this time their primary goal is to find a protective area as we enter into winter.”
Hall said the reason for the increase in horses was not clear.
“The disease has just been worse this year across the nation as a whole … in horses as well as humans,” Hall said. “These things tend to run in cycles, some years just seem to be worse than others and this a bad one.”
Oklahoma was fourth in the nation in the number of equine cases of West Nile Virus, behind Texas, Louisiana and Pennsylvania, according to Bradley, who is also a veterinarian.
Hall said the number of horses that have died as a result of the virus was not known, but that a mortality rate of 30 to 40 percent of those infected is considered typical.
Because the disease is a virus, there is no specific treatment other than to treat the symptoms such as fever, and to ensure that the person, or horse, receives plenty of fluids.
A vaccination is available for horses, but not for humans.
The number of human cases broke the record of 107 cases and nine deaths set in 2007, but Bradley said she's optimistic that 2013 will be a milder year for the disease.
“Based on what we've seen before is usually a season that follows a severe outbreak year is much milder,” Bradley said.
As for the rest of 2012, Bradley said residents should continue taking precautions when outdoors at least until there are several consecutive days of sub-freezing temperatures that drive the mosquito into hibernation.