APPENDIX II-BM:  WNV Decline-DeBess.


This appendix is copied from:‑bin/wa?A2=ind0503A&L=SAFETY&P=12796


[2]USA (Oregon)

Date: Sat 5 Mar 2005

From: ProMED‑mail <>

Source: Statesman Journal online, Associated Press report, Thu 3 Mar 2005






USA: Oregon Faces Tougher Year of West Nile Virus


Oregon's brush with West Nile virus last summer [2004] might have been merely

a primer for what the state will face this year [2005], a health official

said. The mosquito‑borne virus, which has been detected in 8 counties,

sickened birds, horses and 5 people last year [2004]. This year, hundreds of

human cases could be diagnosed if the virus follows the pattern seen in other

states, said Emilio DeBess, a public health veterinarian and epidemiologist

with the Oregon Department of Human Services.


DeBess will convene a summit Tuesday in Portland for public health and

hospital officials from across the state to plan how to deal with a major

outbreak. The virus, which peaks during the summer when mosquitoes are most

active, entered the United States in New York in 1999 and has moved across

the country. It killed 88 people in 2004, according to the national Centers

for Disease Control and Prevention. DeBess and other epidemiologists theorize

that the disease can enter an area in 3 stages. In the beginning stage,

infected birds fly into a state and are bitten by mosquitoes, which in turn

become infected with the virus. During the 2nd stage, the virus spreads

widely among mosquitoes [not, of course, from mosquito to mosquito but

because more of the birds they feed on are infected. ‑ Mod.JW]


The mosquitoes bite a large number of people who become infected. DeBess said

it is likely that Oregon is entering the 2nd stage and will see substantial

numbers of human infections this year. In the 3rd year and beyond, the number

of human cases typically declines rapidly because those who were previously

exposed to the virus acquire an immunity to it. Colorado, for example,

reported 14 human cases in 2002. That ballooned to 2947 in 2003 and then

dwindled to 276 in 2004.


It is impossible for the disease to transfer from an animal to a human or a

human to a human, state health officials said. Cattle, sheep, swine, cats and

dogs appear to be immune [the journalist means resistant to infection; an

animal only becomes immune if it survives infection. One dog in Nevada & one

in New Mexico tested WNV positive in 2004, one cat & 5 dogs in 2003 ‑‑ see

ref. 2004 (12) & 2003 (33) below. Mod.JW]. In humans, most people infected

with the virus exhibit no illness or only mild symptoms such as fever,

headache and body aches. DeBess said that although the number of human cases

declines in subsequent years, the amount of virus circulating among

mosquitoes still is high. "The thing to remember is that the virus circulates

between birds and mosquitoes," DeBess said. "Human beings are dead‑end hosts.

They're just innocent bystanders in this."