West Nile virus facts: Why Texas? How do I tell if I’m infected?

Airplanes loaded with pesticide have taken to the skies above Dallas to combat the West Nile virus, which has infected at least 552 people in Texas and killed 21, according to the Texas Department of State Health Services.

The number is a significant increase from years past: Last year, two died from West Nile in Texas, and seven the year before that.

Medical experts, including some with the Centers for Disease Control and Prevention, shared tips and information on the disease with the Los Angeles Times.
Why has the Dallas region been hit so hard with West Nile?

Dallas has had ideal mosquito-breeding weather, including an unusually warm winter and a rainy season.

What’s being done in Texas to combat the outbreak?

Texas officials declared a state of emergency earlier in the week when the virus broke out and infected more people than in any other state. The declaration created access to state money and resources to fight the outbreak.

This week the planes sprayed some neighborhoods that were hit hardest by the mosquito-borne virus. Ground spraying had already begun in other areas.

What other states have been hit?

No states have had as severe an outbreak as Texas. But according to health department data from various states, there have been 92 cases in Louisiana and six deaths. Mississippi has had 64 cases and one death. Oklahoma reported 61 cases, with three deaths. South Dakota has reported 67 cases, one fatal. And California has reported 26 cases, with one death.

Will the virus continue to spread?

Marc Fischer, a CDC medical epidemiologist based in Fort Collins, Colo., said in an interview that he believed the country was hitting the outbreak’s peak.

What are symptoms of infection?

Those infected with West Nile may develop a fever, headaches, fatigue, rashes and swollen lymph glands. The illness can last a few days to several weeks.

The more serious cases of West Nile can cause encephalitis, meningitis and poliomyelitis. Those diseases have similar symptoms, such as the fever, but can also lead to neck stiffness, disorientation, tremors, convulsions and muscle weakness that can lead to neurological damage, coma, paralysis and death. Neurological damage can be permanent.

Older victims and those with weaker immune systems are more likely to become seriously ill if infected.

Most people infected by West Nile do not show any symptoms. In about 20% of cases, symptoms appear -- usually between three and 14 days after the victim has been bitten, the CDC said.

When should I go to the doctor?

Because the milder cases of West Nile improve on their own, slight symptoms do not necessarily require medical attention, the CDC said.

But more severe symptoms, such as strong headaches or confusion, should be cause for alarm. Seek medical help immediately. There is no specific treatment for the virus, but in the worse cases, patients often need IV fluids, help with breathing or nursing care.

What causes death?

The disease is transmitted by infected mosquitoes. When the mosquito bites a human, the virus makes its way into the blood stream, multiplies and crosses the blood-brain barrier.

In the brain, the virus interferes with the central nervous system and inflames brain tissue.

How do I protect myself?

Avoid mosquito bites and reduce the number of mosquitoes in the areas where you work and play.

The CDC recommends applying insect repellent to skin and clothing. It also suggests staying inside at dawn and dusk, which are peak mosquito hours, and wearing long-sleeved shirts and long pants when outside.

If you’re with children, place mosquito netting over baby carriers and strollers.

Double-check window screens to make sure no bugs can get inside your home or apartment.

Drain standing water in outdoor areas to prevent mosquitoes from laying their eggs there. That includes emptying water from flower pots, pet dishes, swimming pool covers and clogged rain gutters.

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laura.nelson@latimes.com