(NEW YORK) — Los Angeles County is seeing the highest number of West Nile virus cases in nearly a decade, health officials said Monday.
The county has reported 100 cases so far this year. This is the highest figure since 2017 when 268 cases were recorded for the entire season.
The number of current cases is also greater than the five-year average during the same period, according to the Los Angeles County Department of Public Health (LA County DPH).
So far, 94 people have been hospitalized and five people have died, the health department said.
Of the 100 cases, 96 were symptomatic with the most recent onset of illness occurring on Sept. 4, according to LA County DPH.
The health department said that one-third of infected patients live in the East Los Angeles area, about a quarter live in the San Fernando Valley area and about a fifth live in the South Bay region.
It comes as the California Department of Public Health is reporting the highest levels of West Nile virus activity in five years, local health officials said.
So far, the U.S. has seen 671 cases this year across 42 states, according to data from the Centers for Disease Control and Prevention.
The true number of infections is likely higher because cases typically peak in August and September and reporting is delayed.
Public health officials have been warning that rising temperatures have allowed mosquitoes to thrive, increasing the risk of the diseases they spread, including West Nile.
West Nile virus is the leading cause of mosquito-borne disease in the continental U.S., according to the CDC.
Mosquitoes typically become infected with the virus after feeding on infected birds and then spread it to humans and other animals, the federal health agency said.
Risk increases with older age; certain medical conditions such as cancer, high blood pressure and kidney disease; and a weakened immune system.
Most people infected are believed to have lifelong immunity but those with certain conditions may have their immunity wane over time.
Symptoms include fever, headache, body aches, vomiting, diarrhea or rash. Most symptoms disappear, but weakness and fatigue may last for weeks or months.
About one in 150 patients will develop severe disease leading to encephalitis (inflammation of the brain) or meningitis, inflammation of the membranes that surround the brain and spinal cord. Both can lead to death, the CDC says.
Each year, about 2,000 people in the U.S. are diagnosed with West Nile virus, but the CDC says this is likely an undercount because most people either don’t develop symptoms or believe their mild symptoms were caused by another illness.
More than 1,300 people develop severe illness affecting the central nervous system, the CDC says.
There are no licensed vaccines or medications that protect against the virus. The CDC recomemnds using insect repellant, wearing long-sleeve shirts and pants, treating clothing and gear and taking steps to control mosquitoes. The last step includes putting screens on windows and doors, using air conditioning and emptying out containers with still water.
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