MISSOURI, USA — Three people have died and 15 have been hospitalized by West Nile virus in Missouri as of Oct. 4, according to the Missouri Department of Health and Senior Services.

At least 16 cases have been confirmed in the state, but more are under investigation. Health officials said virus levels are the highest the state has seen in recent years.

The mosquito-borne virus is surging throughout the state and across the country, with cases running 40% higher than normal nationwide, according to the Centers for Disease Control and Prevention. More than 770 cases, including 490 severe cases, were identified in early September, compared with the 550 cases, including 350 severe cases, usually reported during this time of year.

“West Nile virus is a serious public health concern, and this year’s increase in cases is a reminder that we must remain vigilant,” said Missouri Department of Health and Senior Services State Epidemiologist George Turabelidze said in a press release on Wednesday. “We are asking all Missourians to take simple but effective steps to protect themselves and their families.”

Health officials said West Nile virus infections often cause no symptoms, but 1 in 5 people may develop a flu-like illness along with fever, headache, and body aches. Older individuals or people with weakened immune systems can also experience brain swelling or paralysis.

The department shared the following ways people can protect themselves from the virus, including: