The Centers for Disease Control and Prevention said that it has seen a surge in mosquito-borne West Nile virus cases at the highest level since 2004, warning people to take extra precautions during the Fourth of July holiday weekend.
At least 48 cases have been reported as of June 30, according to the CDC, and 38 of those have involved “severe neuroinvasive disease.”
“Since 2004, an average of 10 human disease cases has been reported to CDC by the end of June,” the agency stated. “This surge is driven by early circulation of the virus, with 23 states reporting West Nile virus activity.”
The CDC stated that with tens of millions of people expected to spend time outside during the 250th Independence Day holiday weekend, it recommends taking precautions to lower the risk of mosquito bites and transmission of the West Nile virus.
These include using an insect repellent registered with the Environmental Protection Agency, wearing loose and long shirts and pants, avoiding going outside between dusk and dawn when mosquitoes are generally the most active, and using screens on doors and windows, the agency advised.
“These findings serve as an important reminder that mosquito season is well underway,” CDC epidemiologist Erin Staples said in a statement. “As families gather outdoors to celebrate Independence Day, we encourage everyone to enjoy their holiday while taking simple steps to protect themselves and their loved ones from mosquito bites.”
Most of the cases so far this year have occurred in Arizona. Of the state’s 32 total cases, 29 are in Maricopa County. The county, which includes Phoenix, has also recorded four deaths from the virus so far this year.
According to the agency, the virus is the leading cause of mosquito-borne disease in the contiguous United States with around 100 deaths and several thousand cases reported each year, on average. Most people who contract West Nile virus don’t develop any symptoms, the CDC said.
But around 1 in 5 people, or 20 percent, develop a fever and other symptoms, while a smaller number of individuals develop a severe and sometimes fatal illness, including encephalitis or meningitis. Some symptoms other than fever include a headache, body aches, joint pains, vomiting, diarrhea, or rash.
Symptoms generally start two to six days after being bitten by a mosquito infected with the virus, while in some cases it could take two to 14 days, the CDC said. It could take longer for symptoms to begin in individuals with weakened immune systems, the agency added.
“Most people with mild illness due to West Nile virus recover completely, but fatigue and weakness can last for weeks or months,” the agency said, adding that around 10 percent of people who develop severe symptoms die while some effects from the virus can cause permanent damage.
The health agency advised that anyone experiencing a stiff neck, high fever, confusion, tremors, or muscle weakness should seek immediate medical attention. There are no currently available medicines used to treat West Nile.
People aged 60 years and older and those with certain underlying medical conditions are at increased risk of developing severe illness.
The Associated Press contributed to this report.
