West Nile ‘Hot Spots’ Traced

Health officials have pinpointed several “hot spots” in Southern California where the West Nile virus has gained its strongest footholds, areas where they believe humans are most likely to contract the virus.

Experts are predicting the first significant spread of West Nile among humans in California this summer, part of the disease’s gradual spread across Western states. The virus, which has killed almost 600 people in the United States since 1999, is spread by mosquitoes, which contract it by feeding on infected birds.

The “hot spots” are areas where numerous West Nile-afflicted birds and insects have been found in the last few months. The locations have one of two things in common: They have large populations of birds or contain wetlands or other bodies of water that attract mosquitoes.

Officials are alarmed because in just the last few months, birds and insects with West Nile have been moving west from desert areas into cities. Six people in California have tested positive for the virus so far this year, double the number of all of 2003.

“It’s here in higher concentrations in the bird populations than we’ve ever seen before,” said Dr. Jonathan Fielding, director of public health and health officer of the County of Los Angeles Department of Health Services. “We’d expect this to translate into human cases.”

The “hot spots” identified so far are:

* Fontana and surrounding communities. Fontana is home to all six confirmed human cases of West Nile so far this year. The people all contracted the virus in May and are recovering. In this area, more than 200 West Nile-infected dead birds and 11 infected-mosquito pools were found.

* Portions of Arcadia, West Covina and surrounding communities, where dozens of dead birds infected with West Nile have been found. Officials said the area is a prime nesting ground for crows, which are common carriers of the virus.

* Portions of Whittier, La Mirada, Cerritos and Downey, where 64 infected birds as well as several pools of infected mosquitoes were discovered.

* Portions of Riverside and surrounding communities, where 61 dead birds and 2 mosquito pools were found to be infected with the virus.

The state health department and local vector control districts have been combating the disease by posting warning signs telling residents to drain standing water, and educating students and communities on how to avoid contracting the virus.

West Nile arrived in California in late summer last year, mostly limited to sparsely populated areas.

But the virus reappeared this year months earlier than health officials expected. The spread into urban areas has been facilitated by birds.

“We know these areas have a large number of crows that live in these cities, and that may play a part in it,” said Kelly Middleton, spokeswoman for the San Gabriel Valley Mosquito and Vector Control District. “If you have an area where you know you have West Nile-infected birds and a large mosquito population, then you know you have a problem.”

In other states, such as Colorado and Nebraska -- the two that were the hardest-hit last year -- human cases of West Nile occurred first in rural areas. According to the national Centers for Disease Control and Prevention, in 2002, Colorado had 14 human cases and Nebraska had 152.

In the second year, the virus moved into more populated areas, infecting thousands.

Officials have predicted the same could happen in California this year.

“Where there’s a lot of positive[-testing] dead birds, there’s a lot of positive mosquitoes. It increases the risks of acquiring the West Nile virus,” said Stephanie Miladin, spokeswoman for the Greater Los Angeles County Vector Control District.

Recently, the virus was found in the city of Los Angeles. According to harbor-area Councilwoman Janice Hahn, one scrub jay and one mosquito retrieved from the Lake Machado area of Harbor Regional Park in Harbor City were infected.

“We always knew that Lake Machado, that park, would be the place it would come,” Hahn said. “We’ve kind of done everything we could, and it still came.”

Cities in California have taken preventive measures, including educating people on the viral symptoms, encouraging residents to call local or state agencies if they spot a dead bird, and asking doctors to report any illnesses that might be associated with West Nile.

About 20% of victims suffer flu-like symptoms. One in 150 people can develop encephalitis, the swelling of part of the brain, and less than 1% die from the virus. People older than 50 and those whose immune systems are compromised are at greatest risk to become seriously ill, according to the Centers for Disease Control and Prevention.

As with Lake Machado and several other locations in affected areas, city officials have posted signs where infected birds and mosquitoes have been found, instructing residents and pedestrians on how to take precautions.

Health officials said people could reduce their risk of contracting West Nile by wearing insect repellent containing the chemical DEET. They can also wear long-sleeved shirts and pants when outdoors at dawn or dusk -- mosquitoes’ feeding time.

Mosquitoes breed wherever there is standing water, which includes swimming pools and potted plants that aren’t properly maintained, so agencies are asking that people report locations of standing water and get rid of their own.

Middleton said identifying the “hot spots” helps officials focus their control activities. She said poorly maintained swimming pools are common in urban areas and a large part of this summer will go to educating residents on how to clean and drain their pools.

People anywhere, even outside the “hot spots,” are susceptible to the virus.

“I don’t think people should feel that it’s not a problem for them.” Fielding said. “Birds can fly and also, mosquitoes can fly a substantial distance.”