Two more Houstonians die from West Nile virus

The number of ZIP codes where the West Nile virus has been confirmed in mosquito samples has jumped significantly in the past two months. The number of ZIP codes where the West Nile virus has been confirmed in mosquito samples has jumped significantly in the past two months. Image 1 of / 1 Caption Close Two more Houstonians die from West Nile virus 1 / 1 Back to Gallery

The worst outbreak of West Nile virus in Harris County in several years has caused three deaths in Houston, including two reported Tuesday, leading one expert to say more are expected with the peak of the season just about to hit.

Kristy Murray, an infectious disease specialist in Baylor College of Medicine's National School of Tropical Medicine, said it's early in the season for reporting West Nile infections, with 80 percent of the cases typically showing up with onset symptoms during this week, historically the peak of the season. There is a lag from the onset of the disease to when the deaths or infections are reported, she said.

Murray said three deaths is a high number before the peak even hits.

"That's a significant number. We should expect more," Murray said. "We are about to hit our peak and we still have another month when the majority of cases are going to occur."

Texas, particularly the Dallas area, has seen a surge of West Nile cases this year. In Dallas, officials are dealing with the worst outbreak of the virus in the U.S. this year, prompting city leaders to declare a state of emergency. The mayor approved the first aerial spray of insecticide in the city in more than 45 years. More than 200 cases of West Nile and 10 deaths linked to the virus have been reported across Dallas County, where officials authorized aerial spraying last week.

Rain, warm winter

State public health officials have attributed the increased activity to the warm winter and rain. Statewide, 381 cases and 16 deaths have been linked to West Nile.

In Houston, the city posted news of the two recent deaths on its website Tuesday. No deaths have been reported in Harris County outside of the city. Thirteen cases have been reported in the city and six in Harris County.

Kathy Barton, spokeswoman for the Houston Department of Health and Human Services, said the latest West Nile-related deaths occurred in the last three weeks. They involved people between 55 and 74. One of the deaths was the first human infection reported by the city this year, on June 27, and affected a northeast Houston woman. The other incident involved a southwest Houston man whose case was reported on Friday.

This year's first West Nile death was in July and involved a man between 75 and 84 and from southwest Houston.

People who die from the virus typically are elderly or have other chronic health problems, such as diabetes or cancer, Barton said. "Typically a healthy person would not develop a serious infection," Barton said.

The news of the recent deaths comes the day before Harris County is scheduled to spray about 63,000 acres to combat the spread of the virus, which has penetrated nearly half of the county since June. Wednesday's aerial spray will cover portions of west and northwest Harris County.

Dead birds a red flag

Mosquitoes detected with West Nile have been found in 96 ZIP codes and birds with the disease have been in 32 ZIP codes, as of the latest recorded data on Aug. 13.

Harris County public health officials said the disease has been confirmed in more than 300 mosquito samples and nearly 100 dead birds. West Nile was detected in only 13 birds last year in the county.

The increase in bird detections was a red flag, said Harris County's mosquito control director Dr. Rudy Bueno. He said week in and week out, officials have continued to see birds test positive in the areas that will be sprayed.

"When we see the cluster of activity like that, it's a good indicator that aerial treatment would be really beneficial," Bueno said Tuesday. The aerial spraying supplements ongoing ground treatment.

About three-quarters of an ounce of the insecticide Dibrom will be spread per acre. North-east and northwest Houston have traditionally been hot spots for the disease. Such aerial operations have been conducted annually since 2002.

No vaccines to prevent West Nile infections exist and no medications exist to treat the disease. To reduce exposure, health officials urge people to use repellent; wear long sleeves and pants at dawn and dusk when mosquitoes are most active; make sure screens are on doors and windows; and regularly drain standing water.

erin.mulvaney@chron.com