Those relentless rainfalls that pummeled Oregon for months, coupled with warmer weather, are likely to make for a heavy mosquito season this summer.

State specialists are already seeing mosquitoes in southern, central and eastern Oregon, with the insects spreading to other areas as the heat arrives.

The National Weather Service expects hotter-than-usual temperatures to hit Oregon this summer, said Gerald Macke, a weather specialist.

Mosquitoes thrive in heat but they also need water. The females lay their eggs in water. The eggs and larvae can overwinter in freezing temperatures. When the water warms, they hatch and produce more mosquitoes that continue the cycle.

As the snow pack melts, Oregon is likely to have a lot of water for mosquitoes to reproduce, said Emilio DeBess, the state's epidemiologist specializing in mosquito-borne illness.

"The snow pack is huge," DeBess said. "It's the perfect storm for mosquitoes to hatch and females to lay eggs."

Keep mosquitoes away

• Use insect repellents, especially those with DEET, picaridin, IR3535 and oil of lemon eucalyptus. Use especially at dawn and dusk.

• Install or repair screens on windows and doors.

• Wear long-sleeved shirts, long pants, shoes, socks and hats outside, especially in wooded areas.

• Protect infants by putting mosquito netting around strollers.

• Drain standing water from flower pots, tarps, wheelbarrows and anything else that collects pools.

• Fix leaky faucets.

• Change water in bird baths, wading pools and pet bowls twice a week.

A heavy mosquito season increases the chance that Oregon will have more cases of West Nile virus. The insects carry the virus and pass it onto humans when they bite. Most people don't suffer any symptoms but the virus can cause fever and even inflammation of the brain in older people.

"It can be a fairly severe illness," DeBess said.

West Nile rarely kills people but it can be deadly to birds and horses. Though there is no vaccine for people, there is one for horses.

In relatively dry years, West Nile tends to be less of a problem. For example, last year there were four known cases in Oregonians, DeBess said. In 2015, there was only one. That compares with 2006, when a record 73 people were infected.

The virus tends to pose the biggest problem in eastern Oregon.

Officials track West Nile virus by setting mosquito traps around the state. This year for the first time, scientists also will trap and test mosquitoes for the Zika virus.

Zika can be transmitted from a pregnant woman to her fetus, causing severe brain damage in the newborn. The state has had 51 cases of Zika infection in Oregon since January 2016. All of them have involved people who have traveled to Zika-infested areas or who contracted the virus from someone who traveled abroad.

Two types of mosquitoes carry Zika – Aedes aegypti and Aedes albopictus. The latter has been found in Multnomah County.

This is the first year that Oregon has had the ability to test the insects, thanks to a grant from the federal Centers for Disease Control and Prevention.

Mosquitoes that carry West Nile tend to bite at dawn but those that carry Zika attack during the day. The best way to prevent a bite is to use an insect repellent, wear long-sleeved shirts and get rid of standing water near residences.

-- Lynne Terry