Until now, the best weapon against disease-carrying mosquitoes in
the United States has been outdoor pesticide fog sprayed by truck
and airplane. But health experts fear the typical approach will do
little to eradicate the Aedes aegypti mosquito that carries Zika.
Controlling that mosquito requires pesticide sprayed under beds, on
the walls and in closets, said Gonzalo Vazquez-Prokopec, who studies
disease transmission patterns of mosquitoes at Emory's School of
Public Health's Department of Environmental Sciences.
"We know fogging is not effective," Vazquez-Prokopec said.
Though there could be localized U.S. outbreaks, most likely along
the Gulf Coast, federal officials said they hope the wide use of air
conditioning, window screens and regular garbage collection will
mitigate the risk.
The World Health Organization declared the Zika outbreak an
international health emergency this week after evidence linking the
virus to microcephaly, a devastating birth defect that can cause
unusually small heads and permanent brain damage. Brazil has
reported 3,700 suspected cases of microcephaly. The outbreak is now
affecting at least 25 countries and territories, most of them in
Latin American and the Caribbean, and could infect up to 4 million
people in the Americas, according to the WHO.
More than 30 people in the United States have been confirmed to have
Zika after traveling to an affected country. There has been one
report of transmission within the United States, but experts believe
that will increase as the weather warms up, the local mosquito
population multiplies and many more travelers return to the country.
"All it takes is one of those individuals who arrives back in the
United States at the stage where they have virus in their blood,"
said Scott Weaver, an expert in mosquito-borne viral diseases at the
University Texas Medical Branch's Galveston National Laboratory. At
that point, he said, a single mosquito biting the affected person
could spread the disease to others.
White House spokesman Josh Earnest said Monday the risk of
transmission now is "quite low," but as temperatures rise, "we want
to make sure that we have got a strategy to try to limit the spread
of this disease when that happens."
The U.S. Centers for Disease Control and Prevention is working on a
control program for Zika, which will likely involve public education
about eliminating breeding sites and spraying to kill mosquito
larvae and adult mosquitoes, especially in areas experiencing
outbreaks, said spokesman Tom Skinner.
Until then, the CDC is circulating guidelines developed for
combating chikungunya, a close cousin to Zika carried by the same
types of mosquitoes. Local health departments are also sorting out
their approach to fight Zika..
"If it's going to happen, I think it will happen in the warmer
months, likely in April and May," said Dr. Peter Hotez, dean of the
National School of Tropical Medicine at Baylor College of Medicine
Zika thrives in impoverished areas, spreading widely in
garbage-filled neighborhoods and in homes and apartments with no
screens on the windows, conditions that are present in many Gulf
Coast communities in the United States, Hotez said.
The Aedes aegypti mosquito that carries Zika also transmits dengue
fever and chikungunya. Aedes aegypti is mostly found in southern
parts of the United States, such as the coastal regions of Texas,
Louisiana, Mississippi, Alabama and Florida.
Experts believe it arrived on slave trade ships from Africa,
spreading yellow fever in port cities, including a 1793 outbreak in
Philadelphia that wiped out 10 percent of the city's population of
Unlike Aedes aegypti, most mosquitoes common to North America feed
at night and live in wooded areas.
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Recent research suggests the pest may be adapting to colder
temperatures. David Severson at the University of Notre Dame
discovered a population of Aedes aegypti mosquitoes that has spent
the past four winters underground in Washington, D.C.’s Capitol Hill
Aggressive abatement involving indoor and outdoor fogging and
breeding ground eradication between 1947 and 1970 nearly wiped out
Aedes aegypti. At the time, the mosquitoes were the source of yellow
fever in across the Americas. But budget cuts and the development of
an effective yellow fever vaccine ended eradication efforts, and
Aedes aegypti populations rebounded.
Scientists believe Aedes albopictus, or the Asian tiger mosquito,
also is capable of spreading Zika. This aggressive biter arrived in
the United States in 1985 and has replaced Aedes aegypti in some
places. Its range includes at least 32 U.S. states as far north as
Illinois and Pennsylvania and in pockets as far west as California.
Aedes albopictus breeds in small containers of water, bites during
the daytime and lives near population centers. A less picky eater,
it also feasts on pets and wild animals.
Researchers in Brazil are studying whether the Culex species, a
carrier of the West Nile virus commonly found in many southeastern
U.S. states, might carry Zika, which could explain the rapid spread
in Brazil. These mosquitoes rest in the daytime and bite at dusk or
PUBLIC HEALTH PROBLEM
All of this poses a challenge for U.S. health departments, which
have faced pressure to reduce mosquito abatement activities amid
budget cuts and increasing concerns over exposure to pesticides.
"The current methods we have some shortcomings,” said the CDC's Dr.
Anne Schuchat. “We're going to need to work in future on identifying
Brazil's government has mounted a door-to-door campaign and has
authorized public health officials to enter properties by force if
necessary. Health workers search for potential breeding spots and in
some areas use indoor foggers, applying pesticides that stick to
"That is not going to fly in the United States," said Joseph Conlon,
technical advisor for the American Mosquito Control Association,
which represents researchers, public health officials and pesticide
There are no pesticides registered by the Environmental Protection
Agency for indoor application, Conlon said. Instead, abatement will
likely focus on typical breeding sites, from birdbaths to potted
plants, dog bowls, tin cans, tires and other places likely to become
inundated with water.
"Our best bet is to remove the breeding habitats," he said. "It's a
lot harder to do than you would think. People don't want to change
their habits," he said.
(Reporting by Julie Steenhuysen; Additional reporting by Roberta
Rampton in Washington, Ben Klayman in Detroit, Leticia Stein in
Tampa and Suzannah Gonzales in Chicago; Editing by Michele Gershberg
and Lisa Girion)
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