Public health officials have announced 10 new human cases of West Nile virus, bringing to 24 the number of human cases acquired in Massachusetts this year.
The newest reported cases are predominantly among older individuals.
Public Health Commissioner Monica Bharel said Friday that the state has seen four times as many cases compared to last year. She said even with the start of fall and cooler temperatures, mosquito season isn't over. It's not unusual to see people infected in October.
West Nile Virus is usually transmitted to humans through the bite of an infected mosquito. While it can infect people of all ages, people over the age of 50 are at higher risk for severe disease. Most people infected have no symptoms.
According to the U.S. Centers for Disease Control and Prevention, the most effective method to prevent West Nile infection is to wear insect repellent, long-sleeved shirts and pants, and take steps to control osquitoes indoors and outdoors, including emptying stagnant water in planters, birdbaths, and trash containers.
Symptoms can include fever and flu-like illness but while people older than 60 years old are at greater risk, severe illness can occur in people of any age. Those with the highest medical risk are those with medical conditions that include cancer, diabetes, hypertension, kidney disease and who have received organ transplants. The CDC reports one in 10 people who develop severe illness affecting the central nervous system die.
The latest Massachusetts statistics are a marked increase over previous years. Last year, there were six reported cases in the Bay State and 17 in 2016. In 2012, Massachusetts reported 33 cases, its greatest number of cases in a single year, since data collection began in 1999.
Associated Press reports contributed to this story.