ANCHORAGE - Two summers ago a huge hatch of wasps descended on Fairbanks. University of Alaska Fairbanks entomologist Derek Sikes estimated there were about 10 times more yellow jackets that year than normal. Inevitably they bumped into people. School events were canceled because too many kids were getting stung.
For most victims, the wasp stings were merely painful, but for others they were life-threatening. The emergency room at Fairbanks Memorial Hospital that summer treated 178 patients with insect stings, about four times more than normal. Two men died.
Both the infestation and the deaths - the first cases of fatal anaphylaxis resulting from yellow-jacket stings ever documented in Fairbanks - suggested that something in Alaska might be changing. Was it possible the state's warmer climate was attracting more wasps? Or allowing more wasps to over-winter? Or resulting in bigger hatches all summer long?
It was hard to know, said Sikes, who serves as curator of insects at the University of Alaska Museum, since no one is actually counting wasps in Alaska - and one summer doesn't make a trend. But hospitals have been counting insect stings. And that, along with the wild wasp summer of 2006, gave an allergist in Anchorage an idea.
"That was the sentinel event for us to say, 'Ah! Let's take a look,"' said Dr. Jeffrey Demain, the director of the Allergy, Asthma & Immunology Center of Alaska.
What Demain and Sikes finally determined - reported this month in the Alaska Epidemiology Bulletin - is that insect stings in Alaska have been increasing steadily this decade. And they're occurring further north.
Reviewing the billing records of all the state's Medicaid patients, a database that represents about 132,000 Alaskans, Demain found that there had been a seven-fold increase in insect stings in Northern Alaska within the past decade - from an average of 16 people (per 100,000) per year between 1999 and 2001 to 119 people a year from 2004 to 2006.
All other regions of the state, with the exception of Southeast Alaska, rose as well. In the Interior, which includes Fairbanks, insect stings increased from 260 a year per 100,000 patients in 1999 to an average of 437 a year between 2000 and 2006.
Some of the most serious insect stings - such as those suffered by patients treated at the Allergy, Asthma and Immunology Center that Demain heads - have increased five-fold this decade.
"By the time somebody is coming to us, they've had a near fatal event," Demain said. "They're not coming to us because they have a swollen hand."
Getting stung by a yellow jacket or a hornet can be painful for anyone - the Schmidt Sting-Pain Index rates it "similar to getting your hand mashed in a revolving door." But certain other people - roughly 4 percent of the population - are especially allergic to the venom of bees and wasps, Demain said.
"These chemicals not only can cause hives and itching, but they can cause airways to close; the larynx can close. You can have an asthma-like attack."
That's what doctors believe happened to the two fatally envenomed Fairbanks men - one who was 29, another who was 50 - in 2006, according to a scientific paper Demain and Sikes are currently preparing for publication.
That same summer, according to a story that appeared in the Fairbanks Daily News-Miner, state wildlife biologist Jack Whitman set up three homemade yellow-jacket traps - each a plastic soda bottle half filled with water and whitefish - outside his Fairbanks home and caught 3,461 yellow jackets in four days.
There are now about 11 species of yellow jackets in Alaska, and many more species of other types of wasps, Sikes said. That far surpasses the total of two species of wasps observed a century earlier by the 1900 Harriman Expedition to Alaska.
The most prevalent wasps in Alaska are the common yellow jacket (Vespula vulgaris), which usually nests in rodent holes underground, and the aerial yellow jacket (Dolichovespula arenaria), which nests in trees and the eaves of houses and barns.
The time of year you'll most likely see them is late July, when all the female worker wasps - the only ones that sting - are out feeding on nectar and other insects. But right now is the best time to spot the much larger queen, crawling from her winter's nest.
"Last year we were seeing the first queens just about this time," Sikes said. "I've already seen bumblebee queens out."
It's possible, but not certain, that wasp populations are rising in Alaska, considering that average temperatures in northern Alaska have risen about 4 degrees Fahrenheit since 1950, Demain said.
"When we took a look, we found that (2006) was not a one-time deal - that the number of people being stung and requiring medical care because of stings was going up everywhere in the state," he said. "And has been going up steadily since 1999."