Summer is in full swing in Southern California, and after a brief early lull, so is the West Nile virus.

Mosquito samples collected in Sherman Oaks and Porter Ranch tested positive for the virus in the past week, the Greater Los Angeles County Vector Control District announced Saturday.

With only three positive samples this year – including one a week ago – the inevitable annual West Nile virus infestation is off to a slower start in 2018, the district said.

“Last year [at this time] we had 43 positive samples reported,” district Director of Scientific Technical Services Susanne Kluh said in a statement.

Citing the LA County Department of Public Health, the district said West Nile virus is a leading cause of severe infections among area adults over age 50 with chronic illnesses. Symptoms can include fever, headache, body aches, nausea, or a skin rash and can last for months.

Some severe cases also require hospitalization, and about 7 percent of patients with severe complications have died, county officials said.

Health officials recommended that residents take precautionary steps such as:

• Wearing long-sleeved shirts and long pants while outdoors, particularly in areas where more mosquitoes are present

• Using EPA-registered repellents containing DEET, picaridin, or oil of lemon eucalyptus;

• Checking window screens for holes;

• Draining or dumping stagnant water from places like ard and parking lot drains, air conditioner drip pans or buckets and nonfunctional swimming pools;

• Cleaning and chlorinating swimming pools;

• Draining water from pool covers;

• Stocking garden ponds with goldfish or other mosquito-eating fish;

• Emptying and washing birdbaths and wading pools weekly;

• Covering and emptying rain barrels weekly.

City News Service contributed to this story.