WHO had declared global public health emergency, says causal link to brain defects "Strongly suspected" (Microcephaly)
Zika virus disease: Questions and answers
20 January 2016
Where does Zika
virus occur?
Zika virus occurs
in tropical areas with large mosquito populations, and is known to circulate in
Africa, the Americas, Southern Asia and Western Pacific.
Zika virus was
discovered in 1947, but for many years only sporadic human cases were detected
in Africa and Southern Asia. In 2007, the first documented outbreak of Zika
virus disease occurred in the Pacific. Since 2013, cases and outbreaks of the
disease have been reported from the Western Pacific, the Americas and Africa.
Given the expansion of environments where mosquitoes can live and breed,
facilitated by urbanisation and globalisation, there is potential for major
urban epidemics of Zika virus disease to occur globally.
How do people
catch Zika virus?
People catch Zika
virus by being bitten by an infected Aedes mosquito – the same type of
mosquito that spreads dengue, chikungunya and yellow fever.
How does Aedes
mosquito reproduce?
Only female
mosquitoes bite; they are intermittent feeders and prefer to bite more than one
person. Once the female mosquito is fully fed, it needs to rest 3 days before
it lays eggs. The eggs can survive up to 1 year without water. Once water is
available, and small quantities of standing water are sufficient, the eggs
develop into larvae and then adult mosquitoes. Mosquitoes get infected from
people with the virus.
Where can the Aedes
mosquito survive?
There are 2 types
of Aedes mosquito capable of transmitting the Zika virus. In most cases,
Zika spreads through the Aedes aegypti mosquito in tropical and
subtropical regions. The Aedes aegypti mosquito does not survive in
cooler climate temperatures. The Aedes albopictus mosquito can also
transmit the virus. This mosquito can hibernate and survive cooler temperature
regions.
Can the Aedes
mosquito travel from country to country and region to region?
The Aedes
mosquito is a weak flyer; it cannot fly more than 400 meters. But it may
inadvertently be transported by humans from one place to another (e.g. in the
back of the car, plants). If it can survive the temperature climate of the
destination, it may theoretically be capable of reproducing itself there and
introduce Zika virus to new areas.
What are the
symptoms of Zika virus disease?
Zika virus usually
causes mild illness; with symptoms appearing a few days after a person is
bitten by an infected mosquito. Most people with Zika virus disease will get a
slight fever and rash. Others may also get conjunctivitis, muscle and joint
pain, and feel tired. The symptoms usually finish in 2 to 7 days.
What might be the
potential complications of Zika virus?
Because no large
outbreaks of Zika virus were recorded before 2007, little is currently known
about the complications of the disease.
During the first
outbreak of Zika from 2013 - 2014 in French Polynesia, which also coincided
with an ongoing outbreak of dengue, national health authorities reported an
unusual increase in Guillain-Barré syndrome. Retrospective investigations into
this effect are ongoing, including the potential role of Zika virus and other
possible factors. A similar observation of increased Guillain-Barré syndrome
was also made in 2015 in the context of the first Zika virus outbreak in
Brazil.
In 2015, local
health authorities in Brazil also observed an increase in babies born with
microcephaly at the same time of an outbreak of Zika virus. Health authorities
and agencies are now investigating the potential connection between
microcephaly and Zika virus, in addition to other possible causes. However more
investigation and research is needed before we will be able to better
understand any possible link.
Guillain-Barré
syndrome is a condition in which the body’s immune system attacks part of the
nervous system. It can be caused by a number of viruses and can affect people
of any age. Exactly what triggers the syndrome is not known. The main symptoms
include muscular weakness and tingling in the arms and legs. Severe
complications can occur if the respiratory muscles are affected, requiring
hospitalisation. Most people affected by Guillain-Barré syndrome will recover,
although some may continue to experience effects such as weakness.
Should pregnant
women be concerned about Zika?
Health authorities
are currently investigating a potential link between Zika virus in pregnant
women and microcephaly in their babies. Until more is known, women who are
pregnant or planning to become pregnant should take extra care to protect
themselves from mosquito bites.
If you are
pregnant and suspect that you may have Zika virus disease, consult your doctor
for close monitoring during your pregnancy.
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| (Photo link from internet) |
What is
microcephaly?
Microcephaly is a
rare condition where a baby has an abnormally small head. This is due to abnormal
brain development of the baby in the womb or during infancy. Babies and
children with microcephaly often have challenges with their brain development
as they grow older.
Microcephaly can
be caused by a variety of environmental and genetic factors such as Downs
syndrome; exposure to drugs, alcohol or other toxins in the womb; and rubella
infection during pregnancy.
How is Zika virus
disease treated?
The symptoms of
Zika virus disease can be treated with common pain and fever medicines, rest
and plenty of water. If symptoms worsen, people should seek medical advice.
There is currently no cure or vaccine for the disease itself.
How is Zika virus
disease diagnosed?
For most people
diagnosed with Zika virus disease, diagnosis is based on their symptoms and
recent history (e.g. mosquito bites, or travel to an area where Zika virus is
known to be present). A laboratory can confirm the diagnosis by blood tests.
What can I do to
protect myself?
The best
protection from Zika virus is preventing mosquito bites. Preventing mosquito
bites will protect people from Zika virus, as well as other diseases that are
transmitted by mosquitoes such as dengue, chikungunya and yellow fever.
This can be done
by using insect repellent; wearing clothes (preferably light-coloured) that
cover as much of the body as possible; using physical barriers such as screens,
closed doors and windows; and sleeping under mosquito nets. It is also
important to empty, clean or cover containers that can hold even small amounts
of water such as buckets, flower pots or tyres, so that places where mosquitoes
can breed are removed.
Should I avoid
travelling to areas where Zika virus is occurring?
Travellers should
stay informed about Zika virus and other mosquito-borne diseases and consult
their local health or travel authorities if they are concerned.
To protect against
Zika virus and other mosquito-borne diseases, everyone should avoid being
bitten by mosquitoes by taking the measures described above. Women who are
pregnant or planning to become pregnant should follow this advice, and may also
consult their local health authorities if travelling to an area with an ongoing
Zika virus outbreak.
Based on available
evidence, WHO is not recommending any travel or trade restrictions related to
Zika virus disease. As a precautionary measure, some national governments have
made public health and travel recommendations to their own populations, based
on their assessments of the available evidence and local risk factors.
Can El Niňo have
an effect on Zika?
The Aedes
aegypti mosquito breeds in standing water. Severe drought, flooding, heavy
rains and temperature rises are all known effects of El Niño—a warming of the
central to eastern tropical Pacific Ocean. An increase in mosquitos can be
expected due to expanding and favourable breeding sites. Steps can be taken to
prevent and reduce the health effects of El Niño, in particular by reducing the
mosquito populations that spread Zika virus. WHO and partners are working
together to provide support to ministries of health to:
- increase preparedness and response to El Niño;
- strengthen any action that helps control mosquito populations such as source reduction measures targeting main mosquito breeding spots, distribution of larvicide (insecticide that is specifically targeted against the larval life stage of the Aedes mosquito) to treat standing water sites that cannot be treated in other ways (cleaning, emptying, covering), etc.;
- strengthen vector surveillance (e.g. how many breeding sites in an area, percentage of sites reduced) and
- monitor the impact of actions to control the mosquito populations.
Individual
households can also help reduce mosquito populations. Containers that can hold
even small amounts of clear water such as buckets, flower pots or used tyres
should be emptied, cleaned or covered so that mosquitoes cannot use them to
breed (including during severe drought).
What gaps do we
have in our understanding of Zika virus?
Key issues to be
addressed in our understanding of Zika virus disease include:
- Epidemiological characteristics of the virus, e.g. its incubation period, the role mosquitoes play in transmitting the virus and its geographical spread.
- Potential medical countermeasures (including treatments and vaccines) that can be developed.
- How Zika virus interacts with other arboviruses (viruses that are transmitted by mosquitoes, ticks and other arthropods) such as dengue.
- Development of more specific laboratory diagnostic tests for Zika virus that can reduce misdiagnosis that may occur due to the presence of dengue or other viruses in a test sample.
What is WHO doing?
WHO is working
with countries to:
- Define and prioritize research into Zika virus disease by convening experts and partners.
- Enhance surveillance of Zika virus and potential complications.
- Strengthen capacity in risk communication to help countries meet their commitments under the International Health Regulations.
- Provide training on clinical management, diagnosis and vector control including through a number of WHO Collaborating Centres.
- Strengthen the capacity of laboratories to detect the virus.
- Support health authorities to implement vector control strategies aimed at reducing Aedes mosquito populations such as providing larvicide to treat standing water sites that cannot be treated in other ways, such as cleaning, emptying, and covering them.
- Prepare recommendations for clinical care and follow-up of people with Zika virus, in collaboration with experts and other health agencies.
