With
fears of Zika virus reaching new heights — women in some countries, for
example, are being advised not to get pregnant for years — all eyes are turning
toward prevention.
And
experts say that developing a vaccine will be one of the best ways to fight
this virus.
"If
a vaccine is feasible, it would be one of the best ways to combat [Zika virus],"
said Dr. Amesh Adalja, an infectious disease specialist and a senior associate
at the University of Pittsburgh Medical Center's Center for Health Security.
Zika
causes an infection that is usually mild, but officials are concerned that
infections in pregnant women may lead to microencephaly in their children, a
condition that affects the brain and severely affects a child's cognitive
development. The virus was originally seen in Africa and Asia, but has spread
in the last decade to Central and South America, and some Caribbean and Pacific
islands. In recent weeks, health officials in El Salvador, Ecuador, Colombia
and Jamaica have suggested to women that they avoid getting pregnant until more
is known about the risk of microencephaly.
Because
Zika virus hadn't previously been considered a public health threat, there
hasn't been much research done on the virus, Adalja told Live Science.
However,
that doesn't mean that a vaccine is unattainable.
Although Zika virus is relatively new to the Americas,
it's part of a family of viruses called flaviviruses, which includes more
well-known viruses such as dengue, yellow fever and the West Nile virus.
And
there's a lot of existing research on other flaviviruses, Adalja said. For
example, scientists have found ways to replicate human infections with these
other flaviviruses in animal models, so that researchers can study how the
infection progresses and test out possible drugs, he said.
Not
only that, but scientists have a track record of success in making vaccines for
such flaviviruses, which indicates that this family of viruses isn't completely
impervious to vaccination, he said. There are currently vaccines against the
flaviviruses that cause yellow fever and Japanese encephalitis, and these have
paved the way for future vaccines against other flaviviruses, he said.
Still,
as with any new vaccine, the first step for researchers is to devise a vaccine
that triggers a response from the human immune system that can protect people
from future infections, Adalja said. Then developers can move on to questions
of side effects, cost and how long immunity lasts, he said.
And
although the mutations that can occur in viruses over time can pose a problem,
the goal of vaccine developers is to try and target a part of the virus that
tends to not change, he said.
"All
viruses mutate … so it's not a question of whether it mutates" but how
stable Zika virus is in Brazil, for example, Adalja said. In other words, does
it look like the virus is mutating quickly? Some clues to this might be found
by sequencing the genetic material of a virus strain in Central America, and
comparing it to the sequences of strains in other outbreaks in Asia and Africa,
he said.
Adalja
said that, for the time being, research on a vaccine would likely take priority
over looking for drugs that can treat people infected with the virus.
Once
a woman is infected with Zika virus, and the virus is in the blood, it can
cross the placenta and affect the fetus, he said. It would be very
hard to make an antiviral drug that could be administered fast enough to
prevent the virus's effects, he said.
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