Key facts
- Zika virus disease is caused by a virus transmitted by Aedes mosquitoes.
- People with Zika virus disease usually have symptoms that can
include mild fever, skin rashes, conjunctivitis, muscle and joint pain,
malaise or headache. These symptoms normally last for 2-7 days.
- There is no specific treatment or vaccine currently available.
- The best form of prevention is protection against mosquito bites.
- The virus is known to circulate in Africa, the Americas, Asia and the Pacific.
Introduction
Zika virus is an emerging mosquito-borne virus that was first
identified in Uganda in 1947 in rhesus monkeys through a monitoring
network of sylvatic yellow fever. It was subsequently identified in
humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks
of Zika virus disease have been recorded in Africa, the Americas, Asia
and the Pacific.
- Genre: Flavivirus
- Vector: Aedes mosquitoes (which usually bite during the morning and late afternoon/evening hours)
- Reservoir: Unknown
Signs and Symptoms
The incubation period (the time from exposure to symptoms) of
Zika virus disease is not clear, but is likely to be a few days. The
symptoms are similar to other arbovirus infections such as dengue, and
include fever, skin rashes, conjunctivitis, muscle and joint pain,
malaise, and headache. These symptoms are usually mild and last for 2-7
days.
Potential complications of Zika virus disease
During large outbreaks in French Polynesia and Brazil in 2013
and 2015 respectively, national health authorities reported potential
neurological and auto-immune complications of Zika virus disease.
Recently in Brazil, local health authorities have observed an increase
in Guillain-Barré syndrome which coincided with Zika virus infections in
the general public, as well as an increase in babies born with
microcephaly in northeast Brazil. Agencies investigating the Zika
outbreaks are finding an increasing body of evidence about the link
between Zika virus and microcephaly. However, more investigation is
needed to better understand the relationship between microcephaly in
babies and the Zika virus. Other potential causes are also being
investigated.
Transmission
Zika virus is transmitted to people through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti
in tropical regions. This is the same mosquito that transmits dengue,
chikungunya and yellow fever. However, sexual transmission of Zika virus
has been described in 2 cases, and the presence of the Zika virus in
semen in 1 additional case.
Zika virus disease outbreaks were reported for the first time
from the Pacific in 2007 and 2013 (Yap and French Polynesia,
respectively), and in 2015 from the Americas (Brazil and Colombia) and
Africa (Cabo Verde). In addition, more than 13 countries in the Americas
have reported sporadic Zika virus infections indicating rapid
geographic expansion of Zika virus.
Diagnosis
Infection with Zika virus may be suspected based on symptoms
and recent history (e.g. residence or travel to an area where Zika virus
is known to be present). Zika virus diagnosis can only be confirmed by
laboratory testing for the presence of Zika virus RNA in the blood or
other body fluids, such as urine or saliva.
Prevention
Mosquitoes and their breeding sites pose a significant risk
factor for Zika virus infection. Prevention and control relies on
reducing mosquitoes through source reduction (removal and modification
of breeding sites) and reducing contact between mosquitoes and people.
This can be done by using insect repellent regularly; wearing
clothes (preferably light-coloured) that cover as much of the body as
possible; using physical barriers such as window screens, closed doors
and windows; and if needed, additional personal protection, such as
sleeping under mosquito nets during the day. It is extremely important
to empty, clean or cover containers regularly that can store water, such
as buckets, drums, pots etc. Other mosquito breeding sites should be
cleaned or removed including flower pots, used tyres and roof gutters.
Communities must support the efforts of the local government to reduce
the density of mosquitoes in their locality.
Repellents should contain DEET (N,
N-diethyl-3-methylbenzamide), IR3535
(3-[N-acetyl-N-butyl]-aminopropionic acid ethyl ester) or icaridin
(1-piperidinecarboxylic acid, 2-(2-hydroxyethyl)-1-methylpropylester).
Product label instructions should be strictly followed. Special
attention and help should be given to those who may not be able to
protect themselves adequately, such as young children, the sick or
elderly.
During outbreaks, health authorities may advise that spraying
of insecticides be carried out. Insecticides recommended by the WHO
Pesticide Evaluation Scheme may also be used as larvicides to treat
relatively large water containers.
Travellers should take the basic precautions described above to protect themselves from mosquito bites.
Treatment
Zika virus disease is usually relatively mild and requires no
specific treatment. People sick with Zika virus should get plenty of
rest, drink enough fluids, and treat pain and fever with common
medicines. If symptoms worsen, they should seek medical care and advice.
There is currently no vaccine available.
WHO response
WHO is supporting countries to control Zika virus disease through:
- 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 still 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 read more.