West Nile virus detections surpass five-year average in San Gabriel Valley

West Nile virus detections have surged in the San Gabriel Valley after an uncharacteristically warm winter and several heat waves led to an explosion in mosquitoes throughout Southern California.

The San Gabriel Valley Mosquito and Vector Control District said it has found 105 mosquito samples positive for West Nile virus so far this year, higher than the area's five-year average. 

"Although current WNV activity is higher than usual, our teams are purposely equipped to deal with this challenge," said Director of Scientific Programs Tristan Hallum. 

With Labor Day approaching, the vector control district urged residents to take proactive measures this holiday weekend. 

"We strongly encourage residents to tip out any stagnant water around their homes, toss out any unused containers that can collect water, and protect themselves with mosquito repellent when outdoors during this holiday weekend," Hallum said.

Residents should take steps to clear standing water from common places such as buckets, gutters, pet dishes and birdbaths weekly. Officials also urged residents to properly treat their pools, spas and ponds and to report poorly maintained pools to their local vector control district. LA County released this map outlining local vector control, but residents can also call 211 for information.

The Los Angeles County Department of Public Health recommended that residents wear light-colored, long-sleeve shirts and long pants to prevent mosquito bites, in addition to wearing mosquito repellents with the following ingredients:

• DEET
• Picaridin
• IR3535
• 2-undecanone 
• Oil of lemon eucalyptus  

DPH said West Nile Virus is native to LA County and is the most common mosquito-borne disease in the area. With 15 cases documented as of August, public health staff said the number of people infected with West Nile virus, half of whom live in the San Fernando Valley, outpaces the five-year average for this time period. 

LA County reported its first West Nile virus death of the year on Aug. 20. Public health staff said the person was hospitalized with a neurological illness caused by the disease. 

"This tragic loss is a reminder of the serious threat posed by mosquito-borne diseases, including West Nile virus and dengue," LA County Health Officer Muntu Davis said last month. 

West Nile virus is transmitted through bites from infected mosquitoes. The virus lives within several types of birds and spreads through the region when mosquitoes feed on the infected birds. 

Public health staff said people over 50 and residents with health problems are at a greater risk of serious illnesses, including meningitis, encephalitis and limb paralysis. 

There is no specific treatment for the disease and no vaccine to prevent infection, according to DPH. 

Most people infected with West Nile virus do not experience any symptoms, but about 20% develop a fever with symptoms like:

• Headaches 
• Body aches 
• Joint pains 
• Vomiting 
• Diarrea
• Rash

Public health staff said about 1 in 150 will have severe symptoms, such as high fever, stiff neck, muscle weakness and sometimes a rash, about 3 to 14 days after being infected. They urged anyone with these symptoms to call their doctor right away.