LA Sees 'Unprecedented' Spread Of Dengue Fever Spread By Mosquitoes

BALDWIN PARK, CA — Los Angeles has had an unprecedented number of dengue fever cases spread locally among people who have not traveled outside the country, a troubling development in the battle against mosquito-borne diseases in California.

Los Angeles County recorded its first known case of locally transmitted dengue fever last year, and this year, there have already been three cases confirmed with more than two more months of mosquito season still to go. Authorities confirmed two cases this week and one last week in Baldwin Park, the Los Angeles County Department of Public Health of health announced Wednesday.

According to health officials, the three became ill have after being bitten by infected mosquitoes.

“This is an unprecedented cluster of locally acquired dengue for a region where dengue has not previously been transmitted by mosquitoes,” said Barbara Ferrer, director of the Los Angeles County Department of Public Health.

In October and November of last year, single locally acquired cases of dengue were confirmed by health officials in Pasadena and Long Beach.

"These additional cases of local virus transmission are a stark reminder for all Los Angeles County residents that simple steps to prevent mosquito breeding and mosquito bites can lower the risk of mosquito-borne diseases and prevent more sustained transmission in the future," health officials said in a statement.

The illness is generally spread by a bite from an infected Aedes mosquito. Most patients never exhibit any symptoms, but one in four will develop signs including fever, nausea, vomiting, rash and aches and pains to the eyes, joints or bones.

The symptoms generally last no more than a week, and people usually fully recover within two weeks. Deaths from the virus are extremely rare, health officials said.

Health officials noted that the symptoms of dengue often mirror those of other viruses, and they urged health-care providers to be "vigilant for dengue fever in patients with acute febrile illness and test for and report such cases of mosquito-borne diseases."

"Reducing exposure to mosquitoes and the risk for mosquito bites are crucial to preventing transmission of mosquito-borne disease, including dengue fever," Dr. Muntu Davis, Los Angeles County health officer, said in a statement. "This can be as simple as using insect repellent to prevent mosquito bites, eliminating any standing water around your home where mosquitoes can breed, and keeping your home mosquito-free by using or fixing screens on your doors and windows. These straightforward measures can significantly reduce the risk of mosquito-borne disease for both you and your neighbors."

As the summer warmed up, vector control officials detected a lot of mosquito activity in Los Angeles County this year. After last year's case of dengue transmission, officials were on alert this year, Susanne Kluh, General Manager of Greater Los Angeles County Vector Control District told Patch earlier this summer.

Last year Tropical Storm Hillary contributed to the increase of mosquitoes by dumping rain on SoCal during the hot summer months.

"And so if that contributed to the fact that last year we saw transmission, or if this is just gonna be our new normal, that's what we're going to have to wait and see this year," Kluh said in May.

Vector Control officials have been proactive in trying to curb the local mosquito population, especially as the warming climate has brought the Aedes mosquito to Southern California in the last decade.

From May through October, the district is releasing non-biting, sterile male Aedes mosquitoes in the Alpine Village and Sevenhills neighborhoods in Sunland-Tujunga. The males have undergone radiation to sterilize them, Kluh said.

"So they're still pretty capable of flying around and mating and doing all those things, but any kind of genetic material that they deposit with a female mate is so damaged that there will not be any viable eggs out of that union," Kluh said.S "Since females only mate once, once they mate with one of our sterile males, that kind of ruins all her future egg batches."

The goal is to reduce the mosquito population and the spread of the diseases they carry, including dengue, Zika, and chikungunya. Researchers are still measuring the effectiveness of the pilot program. If it works, they are hopeful it will also reduce reliance on chemical pesticides and the expense associated with them.

In the meantime, public health officials said they are working with the city of Baldwin Park and the San Gabriel Valley Mosquito and Vector Control District to provide outreach to residents and offer information about dengue and ways to prevent mosquito bites. The Vector Control District is also increasing mosquito-trapping efforts in the area.

"The city will continue to update the community throughout this process," Baldwin Park Mayor Emmanuel J. Estrada said in a statement. "In the meantime, we urge all residents to use EPA-registered insect repellent, eliminate standing water around your homes and ensure your window and door screens are in good condition. Let's demonstrate the strength of the Baldwin Park community by working together to protect our community and limit the spread of dengue."

City News Service contributed to this report.