Questão 62 - UECE 2º Fase 1º Dia 2017/2

T E X T

    Researchers used genetic
information from Zika virus to follow its
spread among affected regions in South
and Central America and the Caribbean.
[5]    The Zika virus probably arrived in
the Western Hemisphere from
somewhere in the Pacific more than a
year before it was detected, a new
genetic analysis of the epidemic shows.
[10] Researchers also found that as Zika
fanned outward from Brazil, it entered
neighboring countries and South Florida
multiple times without being noticed.
    Although Zika quietly took root in
[15] northeastern Brazil in late 2013 or early
2014, many months passed before
Brazilian health authorities received
reports of unexplained fever and skin
rashes. Zika was finally confirmed as the
[20] culprit in April 2015.
    The World Health Organization did
not declare the epidemic a public health
emergency until February 2016, after
babies of Zika-infected mothers began to
[25] be born with severe neurological
problems. Zika, which is carried by
mosquitoes, infected an estimated 1
million people in Brazil alone in 2015, and
is now thought to be transmitted in 84
[30] countries worldwide.
    Although Zika’s path was
documented starting in 2015 through
records of human cases, less was known
about how the virus spread so silently
[35] before detection, or how outbreaks in
different parts of Central and South
America were connected. Now two groups
working independently, reporting online
May 24 in Nature, have compared
[40] samples from different times and
locations to read the history recorded in
random mutations of the virus’s 10
genes.
    One team, led by scientists in the
[45] United Kingdom and Brazil, drove more
than 1,200 miles across Brazil — “a Top
Gear–style road trip,” one scientist
quipped — with a portable device that
could produce a complete catalog of the
[50] virus’s genes in less than a day. A second
team, led by researchers at the Broad
Institute of MIT and Harvard, analyzed
more than 100 Zika genomes from
infected patients and mosquitoes in nine
[55] countries and Puerto Rico. Based on
where the cases originated, and the
estimated rate at which genetic changes
appear, the scientists re-created Zika’s
evolutionary timeline. Together, the
[60] studies revealed an epidemic that was

silently churning long before anyone
knew. “We found that in each of the
regions we could analyze, Zika virus
circulated undetected for many months,
[65] up to a year or longer, before the first
locally transmitted cases were reported,”
says Bronwyn MacInnis, an infectious
disease geneticist at the Broad Institute,
in Cambridge, Mass. “This means the
[70] outbreak in these regions was under way
much earlier than previously thought.”
    Although the epidemic exploded out
of Brazil, the scientists also found a
remote possibility of early settlement in
[75] the Caribbean. “It’s not immediately clear
whether Zika stopped off somewhere else
in the Americas before it got to northeast
Brazil,” said Oliver Pybus, who studies
evolution and infectious disease at the
[80] University of Oxford in England.
    In a third study reported in Nature,
researchers from 30 different institutions
followed a trail of genetic clues to
determine when and how Zika made its
[85] way to Florida. Those researchers
concluded that Zika was introduced
multiple times into the Miami area, most
likely from the Caribbean, before local
mosquitoes picked it up. The number of
[90] human cases increased in step with the
rise in mosquito populations, said Kristian
Andersen, an infectious disease
researcher at the Scripps Research
Institute in La Jolla, Calif. “Focusing on
[95] getting rid of mosquitoes is an effective
way of preventing human cases,” he
says.
    Previous studies have found traces
of the virus’s footprints across the
[100] Americas, but none included so many
different samples, says Young-Min Lee of
Utah State University, who has also
studied Zika’s genes. The current studies
provide a higher-resolution look at the
[105] timing of the epidemic’s spread, he says,
but in terms of Zika’s origins and
progression from country to country,
“overall the big picture is consistent with
what we suspected.”
[110]    In addition to revealing Zika’s
history, genetic studies are also valuable
in fighting current and future disease
outbreaks. Since diagnostic tests and
even vaccine development are based on
[115] Zika’s genetics, it’s important to monitor
mutations during an outbreak.
Researchers developed quick-turnaround
genomic analyses for Ebola in recent
years, for example, that could aid a
[120] faster response during the next
outbreak.
    In the future, faster analysis of viral
threats in the field might improve the
odds of stopping the next epidemic, Lee
[125] says. It’s possible for a single infected 

traveler stepping off a plane to spark an
epidemic long before doctors notice. “If
one introduction [of a virus] can cause an
outbreak, you have a very narrow
window to try to contain it.”

Science News, Magazine of the Society for Science & the Public. The Zica epidemic began long before anyone noticed. Vol.191, No.12, May 24, 2017, p. 12.

As to unexplained fever and skin rashes in the Brazilian northeast