The battle against the West Nile virus comes to downtown Baltimore early tomorrow as the state launches the first large-scale mosquito-spraying campaign in the city in at least 25 years.
Between 3 a.m. and 6 a.m., weather permitting, two or three state trucks will spray dilute clouds of a common household pesticide across a 2-square-mile area around the Inner Harbor.
The spraying comes 11 days after the discovery of a single dying crow in Federal Hill. The bird later tested positive for the West Nile virus. Two other West Nile-infected birds were found two weeks ago in Baltimore and Howard counties, prompting spraying over the weekend in parts of Relay and Columbia.
No human cases of the West Nile illness and not a single infected mosquito have been reported in Maryland. "This is totally a precautionary measure," said Dr. Peter L. Beilenson, city health commissioner.
The infection - unknown in the Western Hemisphere before it emerged in New York last year - is passed from birds to people through the bite of infected mosquitoes. It produces no symptoms in most adults, and only mild, flu-like symptoms in others. West Nile encephalitis - an inflammation of the brain - is a potentially fatal but rare complication. It has killed only seven Americans, all elderly.
"In Baltimore and nationally, we have far more important and devastating public health diseases," Beilenson said, citing hepatitis A and B, and AIDS.
"Clearly, elderly folks die of the flu at far higher rates than from West Nile virus," he said. "I'm not exactly sure why this one is being covered so much."
Nevertheless, Beilenson said, New York City health officials have credited mosquito eradication efforts for the fact that human cases of West Nile fever in the New York area have gone down this year even though the number of infected birds found has gone up.
The spraying in Baltimore is not being done simply to calm public fears, he said. "This is absolutely a public health measure."
News of the dead Maryland birds broke late last week. Since then, "the West Nile hot line has just been inundated," said state health department spokesman J.B. Hanson.
More than 300 called on Sunday alone, quintupling the previous call rate. Hot line staffing was boosted from one or two, to as many as six people per shift.
Most callers reported sick or dead birds, of which 31 were picked up. None tested positive for the virus.
Health officials said other people were worried about their health because they had been bitten by a mosquito; some asked whether their headaches might be due to West Nile. They were referred to their doctors, or local health departments.
The area targeted for spraying tomorrow is bounded by Fayette Street on the north, Greene and Russell streets on the west, and I-95 on the south. The eastern limits will be at Broadway in the Fells Point area, and Stevenson Street in Locust Point.
The spraying will be postponed if downtown temperatures fall below 55 degrees, or if it's raining. The cost was estimated at $65 to $75 per hour, per truck.
Thirty health department outreach workers were to walk door to door today distributing informational fliers to 10,000 households in the spray zone.
In addition, health officials will answer questions tonight at a meeting of the Federal Hill South Neighborhood Association. The meeting begins at 7:30 p.m., in the rear hall of the Holy Cross Church, 110 E. West St. in Federal Hill.
The pesticide to be used is Permethrin, a synthetic form of a natural pesticide found in chrysanthemum leaves. It is registered with the U.S. Environmental Protection Agency for use in residential areas. It is also used in RID, a common remedy for head lice, and in pet dips for fleas and ticks.
In the city, it will be applied at a rate of 0.006 pounds (two-thirds of an ounce) per acre - about a tenth of the strength normally used in agriculture.
The targeted spray area totals about 1,280 acres. The state trucks will follow north-south streets and rely on wind drift to reach insects on east-west streets.
"We do this in 1,700 communities throughout the state," said Cy Lesser, director of Maryland's mosquito control division. "There's nothing unusual about this other than the fact it is occurring in the city." He could not recall a similar campaign in Baltimore during his 25-year tenure.
Beilenson said the pesticide spray will not leave a residue, and will dissipate in 20 minutes. "We recommend to people that they stay indoors and that air conditioners not be used" as the trucks pass by, he said.
The mosquitoes killed in tomorrow's spraying won't be the last of the season. Lesser said one or two more generations of adult mosquitoes are likely to hatch this fall before the first killing frost - three or four hours of temperatures in the upper 20s - ends the threat.