Two L.A. County residents are sick with West Nile — the county’s first cases of 2019

Two people in Los Angeles County have been diagnosed with West Nile virus, in what officials say are the first two cases in the county this year.

Both people became ill with West Nile, which is transmitted to humans through a mosquito bite, late last month and are recovering, officials said Monday. One lives in the San Fernando Valley and the other in the southeastern region of L.A. County, they said.

“We are glad to hear that these two people are recovering from their West Nile fever infections and wish them well. Every year in Los Angeles County, we see cases of West Nile virus infection, which can be serious, even deadly, especially for people over 50 and those who have existing health problems,” L.A. County health officer Dr. Muntu Davis said in a statement. “Mosquito bites aren’t just annoying, they may make you sick.”

West Nile virus kills Californians every year. Last year, 11 people in the state died of West Nile, and 44 in the previous year.

An Imperial County man died last month after contracting West Nile virus, the first death caused by the disease this year in the state, officials said.

Health officials recommend that people protect themselves from West Nile by applying bug repellent, clearing their yards of standing water that attracts insects and wearing long sleeves and pants at dawn and dusk, when mosquitoes are most active.

Only 1 in 5 people who catch West Nile have any symptoms. But 1 in 150 who are infected develop a serious illness that can be fatal, according to the U.S. Centers for Disease Control and Prevention. Though serious illness can occur in people of any age, it is most likely among people older than 50.

West Nile virus, first detected in Uganda, wasn’t introduced to California until 2003. The first time scientists in the state isolated the virus was in mosquitoes in Imperial County.

Since then, nearly 7,000 Californians have been diagnosed with West Nile virus and more than 300 have died from the illness, according to state data. The virus has become the most prevalent mosquito-borne disease in the United States.

Health experts say that warm temperatures make it more likely for mosquitoes to breed and infect humans with the virus. This year in particular, late spring rains have left standing water, which provides fertile ground for mosquitoes to breed and spread the illness.

To monitor West Nile levels across the state, health workers test mosquitoes for the virus and collect data on dead birds. Mosquitoes transfer West Nile to birds, which can kill them, making the birds a reliable indicator of how many mosquitoes are carrying West Nile in a region.

This year, dead birds that tested positive for West Nile have been found in L.A. County as well as Orange, Sacramento, San Diego, Fresno, Merced, Tulare and San Joaquin counties, according to the state’s West Nile website.