Matt Hutchinson is one of the few people who can say, with conviction, that “it’s been a pretty quiet year so far on the virus front.”
Hutchinson obviously isn’t talking about the coronavirus.
The virus that occupies much of his attention is West Nile virus, an infection spread to people from mosquitoes.
(West Nile virus, quite unlike coronavirus, isn’t transmitted from person to person.)
Hutchinson is manager of the Baker Valley Vector Control District. His job is to control mosquitoes on 200,000 acres, including most of Baker, Bowen and Keating valleys.
Each summer Hutchinson sets out a network of traps to capture mosquitoes so they can be tested for West Nile virus.
In most summers in the past decade or so — 2018 was an anomalous exception — those tests have detected West Nile virus in local mosquitoes starting in July.
Last summer, for instance, the first infected mosquitoes were trapped in Keating Valley on July 9.
Later in the summer, three other “pools” of mosquitoes — a pool consists of 10 to 50 bugs — also tested positive.
In addition, two people who live near Halfway, which is outside the Vector Control District, were infected with West Nile virus.
Both recovered, although one, Pam Hall-Brisk, suffered severe effects and was in intensive care in a Boise hospital for several days in September.
On average about 20% of people infected with the virus have any symptoms, and in most cases those are minor.
As of Friday, Hutchinson said he has sent 92 pools of mosquitoes to a testing lab at Oregon State University, and none was infected with West Nile virus.
According to the Oregon Health Authority, the virus hasn’t been found in mosquitoes anywhere in Oregon this summer. That’s also unusual, as in most recent summers the virus has been confirmed in mosquitoes in several eastern Oregon counties, such as Malheur and Umatilla, before the end of July.
Hutchinson said the lack of positive tests is not due to laboratory issues related to the coronavirus pandemic.
He said he has had no trouble having Baker County mosquitoes tested at OSU, and the results are arriving about as quickly as in previous summers.
One factor that might be contributing to the apparent absence of West Nile virus is the relative scarcity of the species of mosquito — culex tarsalis — that most often carries the virus in Baker County.
Hutchinson said culex tarsalis populations have been below average so far this summer. He attributes this to cool weather in June.
Culex tarsalis numbers generally rise during hot spells, and Hutchinson said he’s been finding more of that species in his traps since temperatures started climbing the past couple weeks.
The sluggish trend is reflected in the number of mosquito pools Hutchinson has mailed to OSU.
So far he has sent 92 pools to the lab. Last year at this time, despite employing the same number of traps, he had already collected 189 pools.
More information about the Vector Control District, including a schedule for spraying to control mosquitoes, is available at www.bvvcd.org. To report mosquito infestations call the district at 541-523-1151.