An Antioch woman, aged 56, was infected with the West Nile virus, the Contra Costa Mosquito & Vector Control District said in a press statement released on Wednesday. This is the first documented human case of the virus in the county in 2008.

The same district said that five birds and two mosquitoes groups, the transmitters of the WNV, have tested positive for virus last week. Three of the infected birds came from Antioch, one came from Brentwood, and the fifth one from Oakley. The groups of insects were from Oakley and Knightsen, Mercury News reported.

This year, a total of 51 dead birds, five squirrels and 23 mosquito groups have been tested positive for the West Nile virus, whose activity is becoming more widespread.

"We usually start hearing about human cases in September and October," asserted Deborah Bass, district Public Affairs Manager at Contra Costa Mosquito & Vector Control District.

The public health agency said the number of human documented cases fell starting 2005, when the WNV has been identified for the first time. The last death caused by the virus in Contra Costa, a suburban county in the San Francisco Bay Area of the state of California, was reported a year later, when two individuals passed away.

However, despite the fact that reports revealed the drop in the number of cases, it doesn’t mean that people are at a lower risk of contracting the virus and falling ill, Bass warns. "Every year is different,” and one isn’t able to predict future circumstances. “Even though the (human) cases are down, the activity is just as high or even higher than it has been in the past," she said.