It's getting to the time of year where health officials are warning people to be aware of mosquitoes carrying West Nile virus. Officials in several states have already reported cases of West Nile.

On Thursday a Boston-area mosquito pool tested positive for West Nile virus during a routine check for mosquitoes.

According to the CDC, the virus is most commonly spread through mosquitoes and has no cure or vaccination. For most people though, there are no symptoms. About 1 in 5 people will develop fever and other symptoms and in less than 1 percent of people infected there is a serious neurological illness that may be fatal.

People with milder symptoms may be able to treat their symptoms with over-the-counter drugs.

Mosquito populations are usually controlled by aerial spraying by the Department of Health and Hospitals.

"We follow a formula with a threshold that determines when we conduct aerial spraying," said Shannon Rider, Ouachita Parish Mosquito Abatement director. "If we see where human transmission crosses that threshold of minimum infection rates we use the planes. We are approaching that threshold. Once we see a certain number of mosquitoes per 1,000 return positive we could begin to see human transmission."

Cases of West Nile virus usually occur between June and September with the majority of cases occurring in August.

People can take precautions from being bitten by mosquitoes by wearing thicker clothing and emptying water containers to limit mosquito breeding around the community. The CDC also advises people to use insect repellents containing DEET, picaridin, IR3535 and some oil of lemon eucalyptus and para-methane-diol.

People especially at risk are those over 50 and people who have a weak immune system.

This year, the season has been pretty mild. According to the CDC, the worst summer for West Nile was the summer of 2012. The disease is known to present itself in all 48 continental states.

According to the CDC, so far 55 cases have been reported - 15 cases coming from California. South Dakota reported nine cases, Louisiana reported six cases, Colorado reported five cases, Arizona and Nebraska reported four cases each, Iowa has three cases and Mississippi reported two cases. Georgia, Missouri, New York, Oklahoma, Tennessee, Texas and Wisconsin each reported one case. Of the 55 cases, 26 exhibited the neuroinvasive disease. There have been three deaths connected with West Nile virus so far this year.

However, cases may be underreported since most people do not show symptoms and non-neuroinvasive symptoms of the virus may present with symptoms similar to the flu.