An Oklahoma County man older than 80 has been confirmed as the first person in the state to die of West Nile virus this year, the state Health Department reported Tuesday.
The man's name was not released.
West Nile virus is a mosquito-borne illness that can lead to serious neurological disease in some cases — although some who are affected will suffer no ill effects.
The state Health Department has issued a public health warning, recommending that residents take precautions against mosquitoes in their area.
Twenty-four new cases of West Nile virus have been confirmed in Oklahoma in the past week, according to the Health Department.
So far this year, Oklahoma County has seen 12 reported cases of West Nile. Overall, there have been 55 cases of the disease confirmed this year in residents in 14 counties. Tulsa County had 14 reported cases, Carter County is at nine and Pittsburg County had seven.
In addition, a spokeswoman from the state medical examiner's office said another death is suspected to be caused by West Nile. The medical examiner received paperwork from a Midwest City doctor reporting that a Seminole woman, Donna Smith, 81, died because of West Nile.
That report has not been confirmed by the state Health Department.
Health Department officials said they do not expect West Nile virus cases to peak until September or early October. The virus' season runs from May to November.
About the virus
State residents who have contracted the virus this year have ranged in age from 12 to 90. The Health Department warns that people older than 50 are at the highest risk for developing the most severe symptoms.
Symptoms of West Nile fever include sudden onset of fever, headache, nausea, dizziness and muscle weakness, according to the Health Department. Swollen lymph glands or a skin rash also can occur with West Nile fever.
A person suffering from the serious neurological symptoms of West Nile virus might suffer from high fever, headache, stiff neck, mental confusion or disorientation, numbness, convulsions and coma. Another symptom is a polio-type paralysis of an arm or leg.
Anyone with these symptoms should seek medical attention, especially within two weeks after mosquito bites.
West Nile virus spikes every three to four years, state health officials said. The rate of West Nile depends on a variety of conditions, including spring rainfall, hot and dry summers and also the level of immunity to the virus that exists in the state's wild bird population.
If there is a large number of birds that have not encountered West Nile virus, when they are bitten, the virus multiples and amplifies in their bodies and tissues. This means that when another mosquito bites an infected bird, the mosquito will then become a carrier of West Nile virus.
As more mosquitoes pick up the virus from birds, that cycle repeats itself and amplifies in nature, said Kristy Bradley, the state epidemiologist.
After 2007 — the last time West Nile spiked sharply in the state — a substantial proportion of the wild bird population that encountered West Nile virus survived and developed antibodies. The next year, when birds were bitten by infected mosquitoes, the antibodies in the birds' bodies suppressed the production of the virus, Bradley said.
But small- to medium-size wild birds have a life span of about two to four years. This means that once new birds hatch, they must again build up immunity to West Nile, Bradley said.