Zika virus is spreading explosively in the Americas, raising alarm bells globally. But why is Zika virus so dangerous? Dr. Kyuho Paul Park, Institut Pasteur scientist working on dengue, explains in this Q&A.

1.  When was Zika virus first discovered?
The Zika virus was first isolated in a rhesus monkey in the
Zika forest, close to Kampala in Uganda, in 1947 . The first
human cases of infection were later identified in 1952, in
Uganda and Tanzania.
The Zika virus is a member of the Flavivirus family (as yellow
fever, West Nile, St Louis encephalitis and dengue viruses).
The associated diseases share the same method of
transmission – a mosquito bite. At the current time there is
no vaccine to prevent Zika virus disease nor medicine to treat
the infection.
Initially considered as a mild disease there have been issues
raised as there is a potential link between Zika virus infection
in pregnant women and microcephaly in new born babies.
(Reference: (1) Dick GW. Zika virus. II. Pathogenicity and physical properties. Trans R
Soc Trop Med Hyg 1952;46:521–34,
(2) Dick GW, Kitchen SF, Haddow AJ. Zika virus. I. Isolations and serological
specificity. Trans R Soc Trop Med Hyg 1952;46(5):509–20)
 How could it spread worldwide?
Zika virus is carried by mosquitos. It is transmitted to human
and causes disease inside. But we still don’t know which
species played the role of reservoir (a long-term host of a
pathogen of an infectious disease).
Human cases of infection were relatively rare until there was
an outbreak in Micronesia (West of Philippines) in 2007. Zika
virus most likely spread “silently” from Africa to Asia because
it has mainly been transmitted through animals.
The issue is Aedes mosquitos transmit Zika virus. While these
species were originally found in tropical and subtropical zones
they are now wide spread and found on all continents except
Antarctica. They are also able to transmit other viruses from
the same family as well as chikungunya. Therefore, it has the
potential to follow the path of the emerging dengue, West
Nile, or chikungunya threats.
There is also a potential challenge in diagnosis of Zika
infection. Because the virus are from the same family, Zika,
West Nile and dengue viruses share common sequences. This
leads to cross reactivity and it may be difficult to distinguish a
Zika infection vs. dengue, etc. Furthermore, clinical symptoms
are complex in each of these diseases. Therefore it is difficult
for non-specialists to distinguish between the infections.
(Reference: Gatherer D & Kohl A. Zika virus: a previously slow pandemic spreads rapidly
through the Americas. J Gen Virol 2015 doi:10.1099/jgv.0.000381)
Why is Zika Virus so dangerous?
Q&A with Dr. Kyuho P. Park, Institut Pasteur scientist working on dengue

2.  When an adult is infected by Zika the symptoms
are usually mild. But why does it have a serious
affect on new born babies?
We are still learning about the Zika virus. Epidemiologic
data give a statistical view of the pathogen’s effect on
populations affected. As the number of cases increase, these
statistics may vary. In addition, several viruses giving similar
pathologies are co-circulating in many at-risk countries,
therefore it is still difficult to clearly describe the Zika
pathology(ies).
The link between pregnant mothers with Zika virus infection
and babies born with microcephaly and other
malformations was suggested recently. In the 2009 CDC
report, this problem was not stated. (see
http://wwwnc.cdc.gov/eid/article/15/9/09-0442_article).
Based on the French Polynesia and Brazilian epidemiologic
data, the 1st trimester of fetus development seem to be the
period most at risk.
In my opinion, this may be due to Zika virus neurotropism.
The virus might be able to circulate in the mother’s body
and infect the fetus, colonize specific developing tissues,
inflicting lasting damages. However, we need time to prove
if this link is real.
(To read more, see Tetro JA. Zika and microcephaly: Causation, correlation, or coincidence?
Microbes Infect. 2016. doi: 10.1016/j.micinf.2015.12.010)
 Is a Zika virus outbreak possible in Korea?
Theoretically, yes.
The risk is present because (1) the Aedes mosquito
subspecies are present in Korea and (2) as the number of
cases increase worldwide the chances of a Zika virus-
infected traveler visiting Korea is high. Or, an infected
mosquito could accidently be brought into the country. (3)
Also, it hasn’t been clearly established if humans can spread
the virus and (4) the Zika virus reservoir is still unknown.
At present time, according to KCDC, there are no cases of
Zika infection in Korea.
 Outbreak map
Why is Zika Virus so dangerous?
Q&A with Dr. Kyuho P. Park, Institut Pasteur scientist working on dengue