While the cool spring kept them away, mosquitoes have been out in biting force in the summer, as a result of warmer weather and frequent rainfall.
"These 85- and 90-degree days, this is prime mosquito weather for activity," said Laura McGowan, spokeswoman for Clarke, a company that provides mosquito abatement services for communities in the area. "Mosquitoes can lay eggs every five to seven days, and they can lay 200 to 300 eggs at a time. When you've got more activity with mosquitoes, you've got more mosquito bites and just more population."
The cooler-than-usual spring had delayed their activity, she said.
"Mosquitoes are not as active in cooler weather, so they're not out there feeding and multiplying and laying their eggs as much," McGowan said.
And if the unusually cold winter killed off any mosquito eggs, the company is not seeing it. McGowan said the winter "was definitely particularly harsh."
"However, mosquitoes, especially those floodwater mosquitoes – those are the ones laid over time – they are very well-protected," she said. "And they are dormant until they get into water from floodwaters. So, we didn't see a huge drop-off of what we would expect necessarily. But it is hard to say what the population was out there."
To get a handle on the situation, Clarke is doing surveillance work along with larviciding, which interrupts the development of larvae or pupa into adult mosquitoes. Clark also will spray or fog for mosquitoes as part of its adult control measures.
"Each community we work with has a trigger for what levels that populations have to be at for adult control to take place," McGowan said. "Of course, the weather conditions have to be right. You can't do adult control if it's pouring rain or if the wind is too high. Right now, we are doing surveillance throughout the Chicago area and coordinating with all the health departments for identification of mosquito pools in different areas that may be carrying the West Nile virus. When you have a hot, dry summer, that's the best recipe for West Nile."
Clarke recently opened its new 27,000-square-foot headquarters in St. Charles.
The West Nile virus was found in a crow in June collected in Campton Township. This is the first evidence of West Nile virus activity in Kane County this year. West Nile virus is transmitted through the bite of a mosquito that has picked up the virus by feeding on an infected bird.
The Fox Valley Park District has been reminding people to take appropriate precautions if they are participating in outdoor park district activities, such as wearing insect repellent and dressing properly.
"You want people to be outdoors, but that's one of the hazards of being outdoors this time of year," said Jeff Long, public relations manager for the Fox Valley Park District. "No one likes to be bitten, but because of the West Nile virus, there is kind of heightened awareness."
Illinois Department of Public Health officials said it's too early to tell whether Illinois will have an abundance of West Nile virus cases this summer.
"Trying to predict what the rest of the season is going to look like is similar to predicting the weather," department spokesperson Melaney Arnold said. "If it's hot and dry, then yes, we would normally see amplification of West Nile virus in mosquitoes. But if it's rainy, that water gets flushed every so often, and the mosquitoes that carry West Nile virus like to breed in stagnant water."
The same would be true if the weather is cool and wet. She said, "in cool weather, the disease does not amplify as much in mosquitoes or as quickly."
During 2012's hot and dry summer, Illinois saw 290 human cases of West Nile virus and 12 deaths related to the disease.
"That was our second-biggest year since we first started seeing West Nile virus in Illinois," Arnold said.
Last year saw 117 human cases of West Nile virus and 11 human deaths. Arnold noted that many factors go into a person succumbing to West Nile virus. Arnold said it "depends on who is bitten, and if they have an underlying health condition."
"The elderly are a little more susceptible to complications and severe cases," Arnold said. "So often times, it does depend on who contracts it."
But she urged that people take precautions, regardless if the weather is hot and dry or cold and wet.
"We certainly don't want people to become complacent with it," Arnold said.
Other precautions include avoiding being outside when mosquitoes are most active between dusk and dawn, and to eliminate standing water around their house. Arnold said "that's where the mosquitoes are going to breed."
"If you've got for an example, an empty flower pot that's collecting water and it sits there for a week or so, then that's where the mosquitoes are going to breed," she said.
Tips to avoid West Nile virus
• Use insect repellents when you go outdoors. Repellents containing DEET, picaridin, IR3535, and some oil of lemon eucalyptus and para-menthane-diol products provide longer-lasting protection.
• Wear long sleeves and pants from dusk through dawn when many mosquitoes are most active.
• Install or repair screens on windows and doors. If you have it, use your air conditioning.
• Help reduce the number of mosquitoes around your home. Empty standing water from containers such as flowerpots, gutters, buckets, pool covers, pet water dishes, discarded tires and birdbaths.
Source: Kane County Health Department