W. NILE HITS MORE ANIMALS HUMAN INFECTIONS IN COUNTY DOWN FROM 2004, THOUGH.

Byline: Eric Leach Staff Writer

SIMI VALLEY - The number of birds and horses infected by West Nile virus has doubled this year in Ventura County compared to last, although the county has had only one human infection reported compared to two in 2004.

The effects of the virus seem to be less severe in neighboring Los Angeles, and officials say there is reason for optimism the disease will taper off in the area in the future.

This year, however, the number of dead birds is particularly high in the eastern end of the county, including Simi Valley, which may be due to the higher temperatures inland from the ocean and because there are more people reporting dead crows.

``We have had more bird cases and more horse cases, but not more human cases at this time,'' said Randy Smith, an environmental health specialist with the Ventura County Environmental Health Division.

``As it crossed the United States we generally saw more cases the second year than the first. With birds and horses that has been true in Ventura County this year.''

The virus appeared in 1999 in New York and spread quickly across the United States, with the problem often getting worse the second year after its appearance, then declining into an endemic state with fewer cases.

``We hope that it goes down in Ventura County in future years, but that remains to be seen,'' Smith said. ``It's still too early to tell.''

He said most of the birds found dead in the county from the virus (21 in Simi Valley, eight in Ventura, five each in Camarillo and Ojai, and four in Moorpark) have been crows.

Through September there had been eight horses infected and 48 dead birds in Ventura County, compared to three horses and 23 dead birds in 2004.

A number of the infected horses have been along the Santa Clara River Valley including the Piru area.

``The warmer part of the county (including inland areas to the east) had the first bird cases and as the summer went on we saw positives in the coastal areas. Through our second year we have seen a lot more positive samples in the warmer part of the county,'' Smith said.

Last year the onset of most of the infections appear to have peaked around August, and now appear to be going down, officials said.

Anne Kjemtrup, a doctor of veterinary medicine and a research scientist with the vector borne disease section of the California Department of Health Services said West Nile virus actually entered Southern California in 2003 and last year was the second year in some counties.

Last year the majority of the state's human cases (more than 700) were in four Southern California counties - Los Angeles, Riverside, San Bernardino and Orange.

This year, areas with more cases per capita have been in north-central counties, including Sacramento.

For example, Los Angeles has about .33 human cases per 100,000 population so far this year compared to 3.4 per 100,000 in 2004. Ventura County has had about .13 cases so far compared to .26 per 100,000.

But Sacramento last year was at .24 per 100,000 population, and this year is at about 13.5, while Glenn County with a very high infection rate north of Sacramento has 45 about human infections per 100,000 population.

``California has a lot of different ecological areas,'' said Kjemtrup. ``We predicted more cases this year in the northern central area because we are seeing this second-year phenomenon.

``The virus had time to establish over winter, so the effects were much greater than the year in which it was first detected. In later years it reaches an endemic state in which it remains with us but with much lower numbers.''

``We expect that the numbers will go down,'' she said. ``If you look at New York, there are certainly a lot fewer cases than there were before.''

In Ventura County, Kjemtrup said, the greater number of birds this year may be partly the result of more people in some areas finding and reporting them.

``Birds have a large area in which they fly. In order to detect a bird you need people there to see them,'' she said, speculating that there are more people in Simi Valley reporting them than in the more rural areas of the county.

She and Smith said Simi Valley also may have more dead birds because the climate is warmer than along the coast.

``It seems that transmission requires a certain number of days when temperatures reach a certain level. The higher temperatures (inland) seem to be more beneficial for the virus, than the coastal areas where it tends to be cooler.''

In 2004, there were 830 human infections in California, 540 infections in horses and 3,232 dead birds. Through September of this year there were already 801 human infections, 431 infected horses and 2,643 dead birds, with the sharpest increases in north-central counties, including Sacramento with 170 human cases through September of this year, compared to only three in all of last year.

Los Angeles County had 331 human infections and 840 dead birds in 2004, but through September of this year had only 35 human infections and 133 dead birds.

Eric Leach, [phone]

eric.leach(at)dailynews.com