It took a bit longer than the “new normal” to get here this season, but West Nile virus turned up recently in the Santa Clarita Valley, according to the latest data from the Greater Los Angeles County Vector Control District.

West Nile virus is endemic in Los Angeles County, meaning it’s here to stay. Each year, it’s detected in the southern part of the county in late spring, and it and moves northward with its mosquito and avian hosts as the summer progresses.

Three sentinel chickens tested positive in Santa Clarita on Sept. 28. Like the proverbial canary in a coal mine, sentinel chickens are placed in specific locations by Vector Control personnel who test their blood every couple of weeks for the presence of antibodies.

Then on Oct. 2, a mosquito sample in Newhall tested positive.

None of the 17 crows known to have died from the virus so far this year was from Santa Clarita.

Across Los Angeles County within the past week, 16 mosquito samples, four American crows and 12 chickens tested positive.

“WNV is still actively transmitting throughout the Southland, and residents are strongly encouraged to take precautions to avoid mosquito bites,” according to Vector Control.

West Nile virus is a bird virus that came to the United States from Africa in 1999 and reached California in 2003. It can cause a brain infection in people, horses and other animals, but only 1 in 5 infected people will exhibit symptoms. According to Vector Control, symptoms usually occur between five and 15 days and can include fever, headache, body aches, nausea or a skin rash. Only 1 in 150 infected people will develop severe symptoms, which can include high fever, muscle weakness, neck stiffness, coma, paralysis and possibly death.

L.A. County’s first human death of 2015 came last month in the San Gabriel Valley.

There is no vaccination for West Nile virus. It can’t be transmitted from human to human except through a blood transfusion.

West Nile virus isn’t the only nasty thing carried by mosquitoes in Los Angeles County.

Yellow fever mosquitoes and Asian tiger mosquitoes are present in L.A. County and can transmit dengue fever. Unlike West Nile, dengue can be transmitted from person to person.

The same mosquitoes can transmit chikungunya, which was brought here in 2013 by some travelers.

St. Louis encephalitis is spread by infected Culex species mosquitoes. It’s endemic to L.A. County, but it hasn’t been a big problem since 1986.

Culex mosquitoes also carry Western equine encephalomyelitis, which attacks the central nervous system of horses and humans; the western treehole mosquito and Australian backyard mosquito carry heartworm, which is usually fatal to dogs and cats.

Here’s what Vector Control says to do to guard against mosquitoes:

* Don’t raise your own mosquitoes. Get rid of containers that have or may hold standing water where mosquitoes can breed.

* Make sure that doors and windows have tight fitting screens to prevent mosquitoes from entering your home.

* Wear light-colored, long, loose clothing, such as long sleeve shirts and pants when outdoors. Keep in mind that mosquitoes can bite through thin or tight clothes.

* Use mosquito netting when sleeping or camping outdoors.

* Stay indoors between dusk and dawn when mosquitoes are most active.

* Apply approved insect repellent whenever you are outdoors, even for a short period of time. Choose a repellent based on duration of activity. Remember when you are sweating, physically active, or getting wet, some repellents may not last long.

How to get rid of mosquitoes:

It’s easier than you think. You can help eliminate mosquitoes by removing stagnant water from these common backyard sources:

* Clogged rain gutter;

* Neglected or out-of-order swimming pool, hot tub, pond, or fountain;

* Containers such as rain barrels, cans, buckets, jars, flower pots, etc.;

* Old tires;

* Any container that can hold water for more than seven days.