After bracing for West Nile virus this year, public health officials in Idaho have been surprised to find not even one case – yet.
“We’ve actually been amazed,” said Jack Bennett, the field operations manager for Ada County’s mosquito abatement program. “It’s just been an unusual year.”
The worst year in recent history for West Nile was 2006, where a rainy spring provided good breeding conditions for the mosquitos that carry the virus. Idaho led the United States for confirmed cases that year. More than 1,000 were reported, and there were 23 related deaths, said Tom Shanahan, a spokesman for the Idaho Department of Health.
From 2007 to 2009, there were one or two deaths related to West Nile in Idaho each year.
After a rainy spring of 2010, Idaho health officials expected another bad year for the disease, which causes fever and aches in most cases but can make some people seriously ill.
But as of Aug. 11, not one case had been reported in Idaho. Health providers are required to tell the state about confirmed cases.
“We’re surprised,” said Shanahan.
West Nile is carried from birds to some types of mosquitos. Last year, tests on 20 pools of water in Ada County found 30 cases of larva positive for West Nile. This year, the same number of tests found none.
Bennett said experts in his office are speculating that the West Nile-carrying mosquitos didn’t get a chance to pick up the disease this spring because cool weather delayed the growth of the insects until the birds had hatched and flown away.
“That’s a possibility; we don’t know for sure,” he said Aug. 11. “All we can tell you is we don’t have any.”
Meanwhile, the state has a bumper crop of mosquitos this summer that are annoying, if not life-threatening. In fact, there are more of those than usual, which keeps the mosquito abatement district busy.
“Our mosquito numbers have really been up because of the wet,” Bennett said, adding that farmers didn’t irrigate in early spring because of the cool weather.
“When it did finally warm up they all did it at the same time, and that gave us a large influx of floodwater mosquitos.”
Ada County spends about $900,000 a year on mosquito abatement. About 90 percent of that money, after wages, goes to treating ponds with larvicide, Bennett said.
West Nile season doesn’t officially end until the first hard freeze, usually in October.
“I don’t think we’ll go through the year without any cases,” Shanahan said.