Zika virus: Everything you need to know

Picture of an 'Aedes aegypti' mosquito, the vector that transmits the Zika virus; Photo by James Gathany

Zika Virus

The World Health Organization anticipates that the Zika virus will spread to all but two countries in South, Central and North America.

Everything you need to know about this virus is outlined below.
 

Zika virus facts

• Zika virus is a virus related to dengue, West Nile, and other viruses.
• Zika virus may play a role in developing congenital microcephaly (small head and brain) in the fetus of infected pregnant women.
• The viral disease was first noted in 1947 in Africa and has spread by outbreaks to many different countries, with an ongoing outbreak in Brazil and Puerto Rico; the first diagnosis of Zika virus in the U.S. occurred in Harris County (Houston), Texas, in January 2016.
• The virus is transmitted to people by a mosquito (Aedes) vector; the risk factor for infection is a mosquito bite.
• The Zika virus' incubation period is about three to 12 days after the bite of an infected mosquito.
• The vast majority of infections are not contagious from person to person.
• The symptoms and signs of Zika virus infections are usually
• fever,
• rash,
• joint pain,
• conjunctivitis.
• The virus infection is usually diagnosed by the patient's history and physical exam and by blood testing (testing for the virus genome; usually done in the United States by the Centers for Disease Control and Prevention [CDC]).
• Treatment is related to symptom control, and over-the-counter medication is used in most infected people.
• Rarely, complications such as dehydration or neurologic problems may develop.
• In Brazil, an outbreak of Zika virus infections may be related to the development of congenital microcephaly; evidence comes from epidemiology and from Zika viruses isolated from amniotic fluid and the brain and heart of an infant with microcephaly.
• The prognosis for most Zika virus infections is good; however, complications such as microcephaly, if proven to be related to the infection in pregnancy, would be a poor outcome for the newborn.
• Prevention of Zika virus infections is possible if mosquito bites from infected mosquitoes are prevented.
• Currently, there is no vaccine against Zika virus infection; however, the possible link to development of microcephaly in the fetus has prompted physicians to lobby for a fast development of a vaccine.

What is Zika virus?

Zika virus is a Flavivirus that is related to dengue, West Nile, yellow fever, and Japanese encephalitis viruses (Flaviviridae); the viruses are transmitted to humans by mosquito bites and produce a disease that lasts a few days to a week. Common symptoms include fever, rash, joint pain, and conjunctivitis (redness of the eyes). In Brazil, the viral infection has been linked to birth defects (mainly small head and small brain size, termed microcephaly) in babies (newborns) whose mothers became infected with Zika virus during their pregnancy.

What is the history of Zika virus outbreaks?

Zika virus (ZIKV) was first isolated and identified in the Zika Forest of Uganda in 1947. Studies suggest that humans in that area of Africa could also have been infected with the virus. From 1951-1981, blood tests showed evidence of Zika virus infections in many other African countries and Indonesia (Tanzania, Egypt, Sierra Leone, Malaysia, Thailand, and the Philippines, for example), and researchers found that transmission of the virus to humans was done by mosquitoes (Aedes aegypti). In 2007, the virus was detected in Yap Island, the first report that the virus spread outside of Africa and Indonesia to Pacific Islands. The virus has continued to spread to North and South America (Mexico, Columbia, Brazil, and into the Caribbean islands). The most recent outbreaks have been noted in Puerto Rico, Cape Verde Islands, and a large ongoing outbreak is occurring in Brazil that started in May 2015 and is ongoing. The first isolation of Zika virus in the U.S. occurred in January 2016 in Harris County (Houston), Texas, from an individual who became infected in El Salvador in November and returned to Texas. Although there have not been documented mosquito transmissions in the U.S., Texas and other states have two mosquito strains that could be capable of transmitting the viruses.
For a map of the world where Zika virus infections occur, see the CDC world map at http://www.cdc.gov/zika/images/zik-world-map_12-31-2015_web.jpg.

What are causes and risk factors of a Zika virus infection?

Zika viruses are the cause of the infection. The viruses are transmitted to humans by infected vectors (Aedes mosquitoes) that also transmit other similar diseases such as dengue and Chikungunya. Theoretically, the viruses may be transmitted through blood transfusions or organ donations although to date there are no reports of this type of transmission; there is one report of possible spread through sexual contact.
The major risk factor to get the infection is being in areas where infected mosquitoes reside and not taking precautions to prevent mosquito bites.

How is the Zika virus transmitted?

Virus is transmitted by infected mosquitoes that act as vectors to infect individuals during a mosquito bite. The viruses are not reported to be transmitted from person to person, although theoretically this could happen in some rare instances (blood transfusions, organ transplants, possibly sexual contact, and from mother to fetus).

What is the incubation period for a Zika virus infection?

The incubation period for Zika viruses is about three to 12 days after the mosquito bite. Symptoms may last about four to seven days. Approximately 60%- 80% of infections do not produce any symptoms or signs.

Is the Zika virus contagious?

In general, the virus is not contagious from person to person; the virus requires a mosquito vector to pass the virus to humans. Theoretically, donated blood and organ transplantation may allow rare person-to-person transmission. Other possible ways may be mother to fetus and under certain conditions, by sexual contact.

What are symptoms and signs of a Zika virus infection?

The symptoms and signs of a Zika virus infection are as follows:

• Flat or raised skin rash
• Fever
• Joint pains
• Conjunctivitis (red eyes)
• Muscle aches
• Headache
• Less frequently, gastrointestinal discomfort with vomiting and retro-orbital pain

What exams and tests do health-care professionals use to diagnose a Zika virus infection?

Health-care professionals will start diagnosis with a history and physical exam; patients should tell the provider about any recent travel to areas where the virus is active. If Zika virus infection is suspected, blood tests (done at the CDC with virus reverse transcriptase-polymerase chain reaction tests or RT-PCR) are likely to be ordered to detect the viruses and to differentiate between similar infections such as dengue fever or Chikungunya virus infections.

Are there home remedies for a Zika virus infection?

Home remedies can help reduce the symptoms of the disease and are as follows:

• Fluids to prevent dehydration
• Over-the-counter medications such as acetaminophen (Tylenol) can help reduce fever and pain
• Rest
• Avoid aspirin and nonsteroidal anti-inflammatory medications (NSAIDs) until dengue fever can be ruled out to reduce the chance of bleeding problems (do not use aspirin to treat children).

What is the treatment for a Zika virus infection?

There is no specific medicine that can treat the viral infection; the treatment is aimed at reducing the symptoms of the disease.

What are complications of a Zika virus infection?

Although complications of the virus infection are rare, some can be life-threatening, such as severe dehydration. Neurological changes can occur; for example, Guillain-Barré syndrome. In addition, a large increase in congenital malformations (mainly microcephaly) has been associated with these viral infections in Brazil and is currently under study.

What are the risks of contracting a Zika virus infection during pregnancy?

The risk to the mother of contracting a Zika virus infection during pregnancy is the same risk for individuals who are not pregnant, but the risk to the fetus to develop an abnormality such as microcephaly (small head and small brain) seems to be elevated in pregnancy, especially in Brazil. However, the definitive cause and effect has not yet been demonstrated. Nonetheless, the epidemiological data in Brazil suggest an association between congenital microcephaly and Zika infection of pregnant women. Zika virus infections first arose in Brazil in May 2015. Pregnant women, especially those in the first and early second trimester, in areas where the disease is prevalent should try to avoid any mosquito bites. Officials in Brazil are concerned since almost 4,000 babies (very unusually high number as compared to similar time periods in which only about 150 babies were diagnosed with microcephaly) have been born with microcephaly since May 2015. In addition, Dr. R. Coeli, a pediatrician in Brazil, has reported Zika viruses isolated from the amniotic fluid of two women and one infant's brain and heart tissue -- results she concludes that tie the Zika virus to microcephaly development. Officials have taken the unusual step to recommend women avoid pregnancy until the cause of the increase in microcephaly is definitively determined. Several agencies are intensively studying this problem.

What is the prognosis of a Zika virus infection?

For the large majority of patients who get the viral infection, the prognosis is excellent with few or no complications developing. However, depending upon the association between the infection and congenital microcephaly being a cause-and-effect situation, the outcome of microcephaly is poor.

Is it possible to prevent a Zika virus infection?

Yes, it is possible to prevent Zika virus infections; this may be done by preventing any mosquito bites as the mosquitoes are the vector for the viral disease. In fact, some governments like those in Jamaica are encouraging residents to prevent infections by avoiding areas where mosquitoes breed, destroying areas where mosquitoes breed (for example, getting rid of old tires that contain water), wearing clothing that covers most of the skin areas of the body, and by using mosquito repellents, such as DEET, oil of lemon eucalyptus, para-methane-diol, or permethrin.

Is there a vaccine against Zika virus?

Currently, there is no vaccine to prevent Zika virus infections.

CDC advisory on travel to areas with Zika virus

On Jan. 15, 2016, the CDC issued a travel alert concerning Zika virus. The CDC recommended that pregnant women avoid traveling to areas with Zika outbreaks, and women thinking about becoming pregnant need to consult with their doctors before traveling to areas with Zika virus outbreaks. Women who must travel to areas with Zika virus outbreaks should consult with their doctors about pregnancy risks and take precautions to avoid any mosquito bites. The CDC is continually updating the world map of the locations where Zika virus outbreaks have and are occurring (http://www.cdc.gov/zika/geo/).

REFERENCES:

Kelly, Janis C. "First Zika Virus Case in Continental United States Confirmed in Texas." Medscape.com. Jan. 11, 2016. <http://www.medscape.com/viewarticle/857072?nlid=96603_3901&src=wnl_newsalrt_160112_MSCPEDIT
&uac=138226AY&impID=953397&faf=1>.

Sweden. European Centre for Disease Prevention and Control. "Rapid Risk Assessment: Microcephaly in Brazil Potentially Linked to the Zika Virus Epidemic." Nov. 24, 2015. <http://ecdc.europa.eu/en/publications/Publications/zika-microcephaly-Brazil-rapid-risk-assessment-Nov-2015.pdf>.

Sweden. European Centre for Disease Prevention and Control. "Zika Virus Infection." Nov. 27, 2015. <http://ecdc.europa.eu/en/healthtopics/zika_virus_infection/factsheet-health-professionals/Pages/factsheet_health_professionals.aspx>.

United States. Centers for Disease Control and Prevention. "Zika Virus." Dec. 31, 2015. <http://www.cdc.gov/zika/>.