Batches of mosquitoes have been gathered for testing and come back positive for the West Nile Virus (WNV) causing a scare of possible increased human cases from last year.

Mosquitoes are infected with WNV from feeding off of birds that carry the virus. From there, animals and humans are infected by the virus from the mosquito. There were 11 confirmed human cases of West Nile virus in 2014, according to the Chicago Tribune.

The virus does not always show up in humans immediately. Usually an infected person falls ill within 3 to 15 days and suffers from symptoms like headaches, fever, body aches, swelling of lymph glands and skin rash.

“The vast majority of people don’t even know that they contracted the West Nile virus because we don’t get sick”, says Alan Taege, MD, an infectious disease specialist.

Symptoms can escalate and the infected person may also experience meningitis and encephalitis. Seeking immediate medical attention at the first signs of the virus can help to prevent worsening stages.

Researchers said that excessive rainfall does not necessarily mean there will be more mosquitoes that will test positive for West Nile virus.

“These are not the typical floodwater mosquitoes you see after it rains. You actually see more of the virus when the weather is hot and dry.”

Cities around the nation are constantly collecting samples from multiples sites in order to gauge whether or not there is going to be an increased risk the virus spreading.

Experts are encouraging people to take precautionary measures in order to minimize the possibility of becoming infected. The most strongly suggested precaution is to reduce the amount of time spent outdoors where mosquitoes are present. They also recommend covering the body as much as possible if it is unavoidable to be outside as well as to wear insect repellant.