Global Health: Houston Braces for Another Brush With the Peril of Zika

Almost everywhere, Year 2 of Zika is looking much less threatening than Year 1. But the risk posed by this virus is far from gone.

According to the Pan American Health Organization, the number of infections has declined precipitously in the Americas, except for Peru, Ecuador and Argentina.

Zika infections are down by more than 90 percent in the Caribbean, Central America and Mexico. Cases of Guillain-Barré syndrome paralysis, linked to infection with the virus, are also down to pre-epidemic levels.

Fewer infections overseas should mean fewer travelers returning to the United States with live virus in their blood, reducing the likelihood of an outbreak here.

Dr. Scott C. Weaver, a Zika expert at the University of Texas Medical Branch in nearby Galveston, described himself as “cautiously optimistic” that the epidemic was fading out.

Still, he warned, “it’s premature to conclude that the danger is over.” Data is limited on infections just over the border in Mexico, and the rainy season — prime time for mosquito breeding — has just begun in Central America and the Caribbean.

Still, it’s a far cry from the situation last year, when a surge of babies born with abnormally small heads in Brazil sowed an international panic. The birth defects were shown to be linked to infection with the Zika virus, transmitted to pregnant women by common household mosquitoes.

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The Texas county traps birds for blood sampling.

Credit
Michael Stravato for The New York Times

As the epidemic crept northward with warming weather, drug companies began testing more than 20 vaccines. The Obama White House fought a bitter battle with congressional Republicans over emergency funding, and the Gulf Coast, where similar mosquitoes had previously caused outbreaks of dengue and chikungunya, braced for the worst.

Ultimately, the country recorded about 5,100 cases, of which about 4,800 were acquired by travelers overseas. Florida reported 218 cases of locally acquired Zika infection, however, mostly in Miami. Texas recorded only six, all in the Brownsville area, abutting Mexico.

Thus far, 216 babies with severe Zika-related birth defects have been born or have died in the womb, 88 of them in the United States and 128 in its territories, mostly in Puerto Rico, according to the Centers for Disease Control and Prevention.

As winter returned, the disease receded from the headlines. This summer, there is no panic in cities like Houston, only uncertainty.

Some pregnant women here are nervous; others are not, despite the city’s efforts to sound the alarm with posters, movie theater ads and other public messages.

Jessenia Rocha, 31, a behavioral health representative at Legacy Community Health, is pregnant with her fifth child. Recently she drove 13 hours to San Luis Potosí, Mexico, for her great-grandmother’s funeral.

“My doctor said, ‘Don’t go,’ but I had to be there,” she said. “So my doctor said, ‘O.K., then wear long sleeves and use repellent.’”

Ms. Rocha stayed only two hours, then drove straight back.

Krystle McConico, 31, a gospel singer expecting her first baby, worries not at all. “Two of my close friends are also pregnant, and we haven’t had one conversation about Zika,” she said. “My physician didn’t mention it at my first appointment.”

Her job has taken her to Africa and Asia without problems. Some of her fearlessness may stem from her belief that God will protect her, she said.

“Also,” she added, “mosquitoes just don’t like me. I can sit on the porch with my mother and father, and they get bitten all over and I get nothing.”

Passive Surveillance

Harris County’s mosquito-control program began during a 1965 epidemic of St. Louis encephalitis and was strengthened after the West Nile virus arrived in 2002.

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A Microsoft-designed smart mosquito trap.

Credit
Michael Stravato for The New York Times

Every day at dawn, workers hoist nearly invisible nets in local parks to capture birds for blood sampling. (West Nile and several other dangerous viruses are found in birds, although Zika is not.)

More than 400 mosquito traps are scattered around the county. Some are baited with dry ice, which emits carbon dioxide, the element of human breath that draws mosquitoes.

Some traps exude the lactic acid-ammonia mix of human sweat, while still others use water to attract egg-laying females.

Officials are also testing high-tech experimental traps made by Microsoft that can tell mosquito species apart. The county has its own virology laboratory, including a $300,000 P.C.R. machine acquired specifically for Zika testing.

The biggest weakness in the county’s defenses is that officials still do “passive surveillance” for cases of Zika infection — meaning they must wait for doctors to report them.

Not every doctor who sees a rash and red eyes thinks of Zika. Test results can take weeks, and doctors often fail to alert the health department to new cases, even though they are legally required to do so.

Months could elapse before the city realizes the virus has appeared. A recent paper in Nature concluded that Zika actually arrived in Miami in March or April, but was not detected until July.

Dr. David E. Persse, Houston’s chief medical officer, said he would prefer to do “active surveillance” — by, for example, testing all blood specimens taken in local hospitals. “But there’s no money for it,” he said.

More than 60 percent of the counties on the Gulf Coast and Mexican border, the areas likeliest to see a Zika outbreak, are rated “in need of improvement” for mosquito control, said Dr. Oscar Alleyne, public health adviser to the National Association of County and City Health Officials.

The $1.1 billion in Zika funding that Congress passed last year runs out in September. The Trump administration seeks to cut the C.D.C. budget by $1.2 billion, to what the agency had 20 years ago.

Many county health departments depend on C.D.C. grants, and they have already been “eviscerated,” said Claude Jacob, president of the health officials’ association. Some 43,000 public health jobs were cut over the last decade.

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Mosquito pupa being cultivated for experiments.

Credit
Michael Stravato for The New York Times

“We need a contingency fund for epidemics,” said Dr. Paul Jarris, chief medical officer of the March of Dimes, which fights for Zika funding because of the danger to infants. “If we have a hurricane, FEMA doesn’t have to wait for months until Congress responds. Not having a fund just doesn’t make sense.”

Money is not the only obstacle to turning back the virus.

If there is no intense epidemic somewhere in the Western Hemisphere this summer, it will be hard to test any candidate Zika vaccine, said Dr. Anthony S. Fauci, director of the National Institute of Allergy and Infectious Diseases.

For a valid study, between 2,500 and 5,000 people — ideally in several locations — must get either a vaccine or a placebo.

“If we get a big, big outbreak, we can get an answer about the vaccine’s efficacy by mid-2018,” he said. “If we don’t, it may take till 2020 or 2021.”

With fewer infections, it may take years to evaluate a Zika vaccine; experts fear that drug makers will lose interest, as they did in producing a vaccine against West Nile. (Although there are no human West Nile vaccines, three are licensed for horses.)

The virus is a great threat to pregnant women, however, and Dr. Fauci said he hoped there would be enough potential customers in middle-income countries like Brazil and Mexico, along with wealthy American tourists and business travelers, to keep vaccine research going.

At least one concern is gone: It now seems clear that the Zika virus will not sweep through Africa or Asia, damaging tens of thousands of babies, as had been feared.

Since Zika was found in Africa in 1947 and detected in spots in Asia in the 1950s, scientists suspect it has circulated silently on those continents for decades, probably misdiagnosed as mild dengue or other rash-causing fevers. If so, most girls may get it in childhood and become immune before entering their childbearing years.

If the Zika virus does reach Houston, it may not spread rapidly for another reason: Though huge, the city is not dense. Real estate is so cheap that even the poorest neighborhoods, like East Aldine and the Fifth Ward, have some grass around each house.

Population density is far lower than in the slums of Brazil or Mexico, where a mosquito can find many victims living almost on top of one another.

Officials do what they can to keep Houstonians on guard. The county’s “Skeeter School Bus” visits schools and playgrounds to enlist children in the cause, since they are effective at nagging their parents to empty birdbaths and clean gutters, said Dr. Umair A. Shah, public health director of Harris County.

But a sense of fatigue is pervasive.

“Last year, as soon as you turned on TV — Zika! As soon as you got to work — Zika!” Ms. Rocha said. “This year, I haven’t seen anything.”

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Global Health: Houston Braces for Another Brush With the Peril of Zika was last modified: July 17th, 2017 by admin

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