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West Nile season starts to subside

Setting It Straight: Due to an editing error, a story about the West Nile virus on Page A1 on Sept. 14 incorrectly described how mosquitoes transmit the disease. Mosquitoes transmit the virus to humans and other animals after feeding on infected live birds.

Sacramento County may have seen the worst of West Nile virus for 2005.

State and local health officials saidTuesday the peak transmission periodhas passed for this season, a year inwhich Sacramento County's high caseloadled the state.

While cases will continueto be logged wellinto October, the numbersof new cases reportedeach week to thestate has begun towane, and with it, a controversialepisode in localpublic health policy.

Sacramento County'sepidemic dominatedpublic health concernsthis summer, igniting anoutcry among people opposedto aggressive mosquitocontrol tactics that included unprecedentedaerial pesticide spraying.

The high infection rate was predictedfor Northern and Central California asearly as last year, after Southern Californiabore the brunt of the virus in 2004.The virus hit this region last year, itspresence signaled by dead birdsin the hundreds.

But this year, West Nile madethe jump to the human populationbecause of a surge in thenumber of mosquitoes, whichspread the disease, feeding ondead birds, then biting humans.Mosquito breeding was aided bya heavy spring rainfall and snowmeltcombined with hot temperaturesin July.

"We are now past the peaktransmission period," said Dr.Vicki Kramer, chief of the vector-bornedisease section of the stateDepartment of Health Services."However, the public needs tokeep in mind, based on our experiencelast year and on those ofother areas, that people can get infectedin September and October."

Statewide, the total of humancases Tuesday reached 618 for2005, an increase of 19 percentfrom 521 a week ago.

Sacramento County reportedTuesday a total of 135 cases, up19 since last Tuesday, a 16 percentincrease. That differs dramaticallyfrom the weekly jumpsin August, when case totalsbounced by 20 to 50 percent."This is a cautious comment,"

said county health officer Dr.Glennah Trochet, "but it lookslike we have had fewer (recently)than we have had in the past. Butone point in time doesn't make atrend."

While it appears the number ofnew cases statewide is dropping,Kramer also cautioned that untilthe first hard, cold rain, it's stillWest Nile season.

Data collected so far can be misleadingbecause it can be a monthor more before a case shows upon the record books, she said.The incubation period for WestNile virus is about five to 14 days.

A person can get bitten, not getsick for a week and not seek medicalattention until symptomsworsen.

Last year, the peak period oftransmission occurred in the firsttwo weeks of August, Kramersaid. She suspects this year'speak occurred in the latter twoweeks of August, the delay due toa spate of cooler weather, whichslowed virus transmission.

Symptoms of West Nile virusmay include fever, headache,body aches and rash - some ofwhich can be debilitating and lastup to several weeks. But only 20percent of those infected willever experience symptoms.

The more serious infections,which can affect the central nervoussystem and result in meningitis,encephalitis and a polio-likesyndrome, affect only 1 in150 people infected. Symptomsof the more serious infectionsmay include a stiff neck, slight orpartial paralysis, altered mentalstatus and coma.

Trochet and Kramer creditedmosquito control efforts for whatappears to be a relatively mildWest Nile virus season comparedto other states during the heightof their infections.

Kramer cites Colorado, a farless populous state, where nearly3,000 people became infected in2003, leading to 63 deaths. In California,nine people have diedfrom West Nile virus this year, includingone Sacramento Countyman. The most recent death, thatof an unidentified elderly womanin Kings County, occurred lastweek.

"The important point here isthat without the intensive mosquitocontrol in California, I amquite certain we would be seeingmore illness and death associatedwith West Nile virus,"Kramer said.

The sudden spike in SacramentoCounty cases thrust theSacramento-Yolo Mosquito andVector Control District to centerstage. Unprepared for public scrutiny,the district neverthelessstuck by its spraying strategy.

The district's aggressive approach- which in SacramentoCounty included unprecedentedaerial spraying of pesticides in urbanareas - generated protestsand criticism.

Protesters questioned the potentialeffects of the poison onchildren, pets, cars and otheritems exposed to the outdoors.And they grew increasingly frustratedas planned spraying wasthwarted night after night byhigh winds.

The complaints led to an agreementamong mosquito and vectorcontrol officials to better informresidents of mosquito controlefforts on the ground and inthe air.


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