This year, 21 mosquito samples collected by the San Gabriel Valley Mosquito & Vector Control District have tested positive for West Nile virus, officials said this week.

The control district collected the following number of samples from these cities:

• Azusa: 1

• Baldwin Park: 6

• Bradbury: 1

• Claremont: 1

• Covina: 2

• El Monte: 1

• Glendora: 1

• Irwindale: 3

• La Puente: 3

• Monterey Park: 1

• Pomona: 1

According to the district, the most common source of mosquito bites happen in residents’ yards and patios.

“As warm temperatures continue into September, so does mosquito activity,” Director of Communications Anais Medina Diaz said in a statement. “It’s important that residents continue taking precautions to protect themselves and their family against mosquito bites and mosquito-transmitted diseases like West Nile virus.”

Symptoms of West Nile virus can include fever, headache, body aches, nausea or skin rash. Infection sometimes leads to hospitalization, according to the district.

Residents should tip out stagnant water around the home weekly, toss unused containers that can hold stagnant water and protect against bites by using repellent that contains one of Picaridin, DEET, Oil of Lemon Eucalyptus (or PMD), or IR3535.

For more information, visit sgvmosquito.org.