Predictions that West Nile Virus would be worse in Idaho this year than in 2004 have proven accurate, as both human and horse infections have increased significantly.
Twelve people and 75 horses have tested positive for the virus in Idaho so far this year, up from three humans and 42 horses last year.
Blaine County reported its first cases of West Nile last week, when two horses were found to have contracted the virus. Eleven other counties in Idaho have reported the virus. No human deaths have been reported in Idaho.
West Nile virtually exploded across the state last week, when five people, 20 horses and one bird tested positive.
"Things are heating up," said Karin Frodin, a nurse epidemiologist with South Central District Health, which includes Blaine, Camas, Cassia, Gooding, Jerome, Lincoln, Minidoka
and Twin Falls counties. A Gooding County woman in her 60s and a Twin Falls County man in his 30s tested positive for the virus this month.
Frodin said infections will continue to rise until a cold snap kills mosquitoes, which transmit the virus to mammals and birds.
Health officials say the disease is easy to predict, as areas that are infected one year naturally become worse the following year. Infected mosquitoes pass the disease on from year to year through their eggs, which can survive the winter. Fordin said there is no end in sight and the disease will likely worsen with each successive year in Idaho.
But Frodin said health departments are "learning a lot as this thing evolves."
While there isn't a vaccine for humans, there is for horses, which are highly susceptible to the infection. Dogs and cats are not as susceptible, but Frodin said they can contract the virus. Once humans contract West Nile, they become immune to the disease.
The first case of West Nile was reported in New York City in 1999. Since then, it has spread west with migrating birds. Mosquitoes contract the disease after feeding on infected birds.
While the majority of people infected by West Nile will never experience any symptoms, which are flu-like, the elderly and people with weak immune systems can become fatally ill. So far this year, four people in Idaho have required hospitalization. No deaths have been reported.
While the virus can't be controlled, Frodin said it can be prevented.
People are advised to wear insect repellent and cover their skin when outdoors in the morning and evening, when mosquitoes are at their worst.
People are also advised to remove standing water¾breeding grounds for mosquitoes¾on their property.
As of Sept. 6, 821 human cases of West Nile Virus had been reported in the country—18 people have died.
