It’s not just humans who can
travel rapidly across the world. Viruses and disease-spreading insects
and animals can hitch a ride on various modes of travel and the ongoing Zika virus outbreak has spotlighted how viruses can span the globe, putting at risk people who had formerly been protected by geography.
The
current viral outbreak was first reported in May 2015 in Brazil when
the first confirmed cases were disclosed. But the cases quickly
increased and now government officials believe that more than 1 million
people have been infected in that country. World Health Organization
officials said today that one reason for the rapid spread is that both
people and mosquitoes have no immunity to the virus that is new to the
region.
In a study published
in June 2015 in the Memórias do Instituto Oswaldo Cruz medical journal,
Brazilian researchers found that the genetic profile of the virus is
linked to the Zika virus found in French Polynesia, a group of islands
in the South Pacific.
This
means the virus likely traveled to Brazil via an infected traveler who
was then bitten by a mosquito, which then spread the virus.
While
it’s not entirely clear when the viral outbreak started or if there was
“patient zero” who spread the virus, researchers who published the June
2015 study speculated that the virus may have come to Brazil during
major sporting events that brought together tens to hundreds of
thousands of international travelers in close proximity.
“One plausible hypothesis is the arrival of the new emergent virus during the soccer World Cup
in 2014,” said the authors of the June 2015 study that studied the
genetic sequence of the Zika virus in the Brazilian outbreak.
Another
researcher in a paper for the U.S. Centers for Disease Control and
Prevention's Emerging Infectious Diseases Journal pointed to the Va’a
World Sprint Championship, a canoe race where four participating teams
were from French Polynesia, as a possible place where the infection
started.
Armbruster said the evidence is strong that it may have
been an infected traveler from French Polynesia because the samples are
from an Asian strain of the virus. However, he clarified that
researchers cannot be certain it was related to the big sporting events.
“It
is very likely an infected traveler from French Polynesia that traveled
to Brazil was likely the source of the Brazilian invasion,” he said.
“Whether it is someone associated with the [World Cup,] we do not know
for sure.”
The current Zika
virus outbreak in Brazil is a significant public health concern given
the upcoming Olympics in Brazil, Armbruster said. If travelers to Brazil
are infected and then bring the virus back to areas where the mosquito
species Aedes aegypti is established, that could raise the possibility
of local transmission of the virus.
The symptoms of the Zika virus
are mild and include a flu-like illness with fever, rash, joint pain and
red eyes. However, for pregnant women infected with this virus, it has
been linked with babies that are born with small heads and
underdeveloped brains -- a condition called microcephaly.
Officials
are also investigating if the virus is associated with Guillain-Barré
syndrome, which can cause muscle weakness and paralysis.
Dr.
Bhavini Murthy is a preventive medicine physician at University of
North Carolina-Chapel Hill and a resident in the ABC News Medical Unit.