Mosquitoes trapped near Grandview earlier this month had the potentially deadly West Nile virus, and health officials are warning the public to take precautions.

It was the first positive for West Nile in the state this year, although the presence of infected mosquitoes in the Yakima Valley is becoming commonplace. There has never been a report of a human death from the virus since it was first detected in the region in 2005.

Nevertheless, health officials warn there is a need to stay vigilant as the mosquito season gets intertwined with the hottest months of the summer.

“It’s not anything new for us. It is a little earlier (in the year) than usual,” said Laura Charters, an environmental health specialist with the Yakima Health District. “Hopefully that won’t translate into any human cases.”

Because mosquitoes can breed quickly in very small amounts of water, minimizing mosquito breeding grounds by regularly emptying anything that holds standing water may be the best way to reduce the chance of getting the virus.

Receptacles include flower pots, buckets, trash cans, toys, kiddie pools, pet dishes, animal troughs and used tires. Fixing leaks in outdoor faucets and sprinklers and unclogging roof gutters also helps.

Mosquitoes are most active at dusk and dawn. Health officials suggest wearing long-sleeved shirts and pants outside during those times and using approved mosquito repellents.

Initially discovered in the United States in 1999, West Nile virus has spread rapidly across the country. In 2006, more than 1,000 people were sickened in Idaho and 23 died.

To date, there has not been a documented fatality in Washington State. Charters said there have been only three confirmed illnesses from the virus, one in Clark County and two in Pierce County. All three cases happened in 2006, four years after the virus was first detected in the state.

Most people who are bitten by infected mosquitoes, which get the virus from birds, do not get sick. About 20 percent will develop a mild flu-like illness that typically goes away after a few days.

However, about 1 in 150 can have severe symptoms that include headaches, high fever, muscle weakness, paralysis and coma. The young and old are the most susceptible.

Health officials also warn that owners of horses, which are more susceptible to West Nile than humans, need to get their animals vaccinated against the virus every year.

The infection kills about one-third of infected horses. Most survive without showing symptoms. Last year, all eight infected horses reported in Washington came from Yakima County.