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 Zika is spreading rapidly in Puerto Rico and is expected to peak in
late summer and early fall. By year's end, public health officials
estimate, hundreds of thousands of people will have been infected.
It is the only part of the country that is experiencing a major
local outbreak, but the virus is expected to reach southern U.S.
states within weeks with warmer temperatures and rising mosquito
populations.
Health officials from across the United States are gathering today
at the headquarters of the Centers for Disease Control and
Prevention in Atlanta to outline a national strategy for combating
Zika. In a measure of the concern surrounding the outbreak in Puerto
Rico, CDC director Tom Frieden toured the island, meeting with top
health officials and local experts last month to assess the
situation first-hand.
Puerto Rico is beset with problems already hampering the response:
abundant mosquitoes, high levels of insecticide resistance and
economic woes that have left vector control in shambles.
"We don't have good surveillance" here, Frieden said in an interview
at the Puerto Rican health department in San Juan during his tour.
“We don't have good control measures."
First detected in Brazil last year, the Zika outbreak is spreading
through the Americas. The World Health Organization declared a
global health emergency last month because of growing evidence that
Zika can cause microcephaly, a rare birth defect defined by an
unusually small head. In adults, the virus has been linked to the
typically rare autoimmune disorder, Guillain-Barre syndrome.
EARLY LESSONS
Fighting Zika in Puerto Rico is complicated by the toll of a
decade-long recession. Nearly half of its 3.5 million residents live
in poverty, and mosquitoes are an accepted nuisance. Puerto Rico has
seen repeated outbreaks of dengue and more recently, chikungunya.
Both viruses are carried by Aedes aegypti, the same species of
mosquito that carries Zika.
"Here in Puerto Rico, we're really starting from square one," said
Audrey Lenhart, a CDC vector control expert in an interview at the
CDC's Emergency Operations Center in San Juan.
In its latest report, the Puerto Rican health department said there
are now 350 confirmed cases of Zika infection, including 40 pregnant
women.
"We have a very serious combination of problems," said Dr. Alberto
de la Vega, an obstetrician specializing in high-risk pregnancies at
San Juan's University Hospital at the Puerto Rico Medical Center.
"If you don't have access to money to buy repellent, to sleep with
an air conditioner on so mosquitoes won't bite you, to have mosquito
nets around you and you live in areas where there's more stagnant
water, obviously you have higher risks," he said.
To mitigate the risk of microcephaly among newborns, the CDC and the
Puerto Rican government are distributing Zika protection kits to
pregnant women that include condoms to prevent sexual transmission
from an infected partner, insect repellent, bed nets and larvicide
tablets for standing water that cannot be drained.
De la Vega says many locals are resigned to the idea that everyone
in Puerto Rico will be infected. He said he won't accept that people
are "surrendering like that."
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NO VECTOR CONTROL
Government mosquito abatement resources are scarce, with fewer than
a dozen trucks equipped with insecticide sprayers. Of the
municipalities that do have trucks, most are used to kill nuisance
mosquitoes that bite but do not carry disease, said Manuel Lluberas,
a Puerto Rico-born entomologist who works at H.D. Hudson
Manufacturing, a maker of spraying equipment.
Lluberas, who advises the WHO and the World Bank on vector control
programs, said there are a few municipalities that spray insecticide
once every seven to 10 days or once every few weeks. Spraying "needs
to be done a lot more frequently” to be effective, he said.
Scientists at CDC's Dengue Laboratory in San Juan have been testing
insecticides on mosquitoes gathered from 17 sites on the island.
Frieden said in one of the experiments, mosquitoes placed in bottles
coated with a commonly effective insecticide "were happily flying
around."
Eliminating Zika will require spraying insecticide indoors on walls,
under beds, behind furniture and inside closets, where Aedes aegypti
hide. So far, only two insecticides - deltamethrin and bifenthrin -
are approved for indoor residual spraying, and researchers have
found high levels of resistance to bifenthrin in Puerto Rico.
Mosquito experts have found similar resistance in parts of Texas and
California.
"You find resistance in mosquitoes in one locale, and 20 miles away
they are not resistant," said Joseph Conlon, technical advisor for
the American Mosquito Control Association, which represents
researchers, public health officials and pesticide makers.
Dr. Janet McAllister, a CDC entomologist, said indoor spraying
campaigns will be carried out by local contractors, who will target
only areas where the mosquitoes hide instead of coating entire
walls, as is typically done to control mosquitoes that carry
malaria. "People would not really be coming into direct contact with
those surfaces," McAllister said.
She said the CDC does not plan to use experimental methods,
including genetically modified mosquitoes, such as those from
Intrexon's Oxitec now being tested in Brazil, or those infected with
Wolbochia bacteria that prevent Zika transmission.
Given the urgency of the outbreak, health officials need to focus on
known methods of curbing mosquitoes "rather than doing research on
things that may or may not work," she said.
(Reporting by Julie Steenhuysen; Editing by Michele Gershberg and
Lisa Girion)
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