A San Gabriel Valley resident was among the country’s five first human cases of West Nile virus infection on Los Angeles County this year.

The San Gabriel resident is among the five unidentified victims who tested positive for the virus, while the four others were from San Fernando Valley and the South Bay areas, County Health Spokesman Allen Solomon told the Patch.

The two victims were in a hospital recovering from a serious illness, while the other three were about to donate blood when the virus was discovered in their system, 89.3 KPCC reported.

“They didn’t know they’d had any disease, which is not uncommon, because about 85 percent of those that get West Nile from a mosquito bite don’t know they’ve had any problem at all,” Dr. Jonathan Fielding, the county’s public health director, told 89.3 KPCC.

All the five victims were currently recovering from the infection, the radio program added.

This year, the West Nile virus was reported in 31 California counties. Its highest number of cases for a year was in 2005 when the health department received 880 cases.

“This is just the very beginning of the season,” Fielding told 89.3 KPCC. “Last year we had the second highest number that we’ve ever had [for L.A. County], so it’s really hard to tell what we’re going to have this year. The pattern in other places as well has not been, you know — you can’t predict from one year to the next.”

Mosquitoes that feed on dead birds may obtain West Nile virus and transmit it to human being through mosquito bites.

Although less than one out of 150 or no more than one percent of West Nile victims suffer severe sickness, the virus may result to encephalitis or death, the Patch cited the Centers for Disease Control and Prevention.

One out of five people infected by the virus may experience symptoms such as skin rash, fever, nausea, headaches and swollen lymph glands.

The health department reminded the public of the “Three D’s” as precautions against the virus: “DEET” or the use of repellents with DEET content, “Dawn and Dusk” or the avoidance of outdoor activities during this time of the day when mosquitoes are most active, and “Drain” which is the removal of sources of stagnant water in one’s home, 89.3 KPCC reported.

“We are entering the period of increased transmission of this virus that can cause serious disease,” Fielding told the Patch. “Taking a few simple precautions can greatly reduce the risk of mosquito bites, the primary pathway to human infection.

Health officials said other precautions against the virus include wearing long-sleeve shirts and pants whenever one goes outdoor and the use of tight-fitting screens on doors and windows, the Patch reported.