Public Health

What you should know about Zika virus

A world-leading infectious disease expert writes about transmission, diagnosis and prevention

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Elsevier's Zika Virus Resource Center

This story is part of Elsevier's Zika Virus Resource Center, which contains continually updated resources from Elsevier's content and experts. Visit it here.

Zika virus is a mosquito-transmitted flavivirus which has been known to cause outbreaks of disease in Africa, Southeast Asia and the Pacific Islands prior to 2015. In 2015, widespread Zika virus outbreaks were detected in South and Central America; and as of January 2016, Zika outbreaks involve 18 countries and territories in the Americas.

Zika outbreaks are occurring in many countries, and the virus is expected to spread further. (Source: <a target="_blank" href="http://www.cdc.gov/zika/geo/index.html">Centers for Disease Control</a>)

How dangerous is the virus?

Zika virus is a mosquito-transmitted flavivirus which has been known to cause outbreaks of disease in Africa, Southeast Asia and the Pacific Islands prior to 2015. In 2015, widespread Zika virus outbreaks were detected in South and Central America; and as of January 2016, Zika outbreaks involve 18 countries and territories in the Americas.

Generally, Zika virus is a mild self-limited disease consisting of fever, maculopapular rash, arthralgias and conjunctivitis. Illness generally lasts from a few days up to a week. Approximately 80 percent of Zika infections are estimated to be subclinical (without symtoms).

In the current outbreaks, Zika has been associated with neurological illnesses and postnatal complications. The neurological illness most frequently seen has been Guillain-Barré Syndrome, a reversible illness that causes tingling and sometimes severe weakness. The postnatal complications that have been observed are microcephaly and intracranial calcifications. These devastating birth defects have given rise to much of the recent public concern about Zika. In Brazil, these occurred significantly more frequently in areas that had Zika outbreaks than would  have  ordinarily  been expected in areas without outbreaks.

While Zika virus infection has been detected in fetuses with the above complications, the overall risk of Zika fetal infection and the impact of gestational age on such risks are not completely understood. These topics are under intense investigation.

How is it transmitted?

The Zika virus is transmitted by the Aedes species mosquito (A. aegypti and A. albopictus), which also spreads dengue and chikungunya viruses. (Source: Centers for Disease Control)The transmission of Zika virus is primarily by Aedes aegypti mosquitos, whose natural habitat is in warm climates. It is of concern that Aedes albopictus, which lives in temperate climates, may also become able to transmit the virus; if so, this might result in spread of infection to areas not currently involved with Zika outbreaks. Possible sexual transmission of Zika virus infection has also been reported.

How is the virus detected?

Laboratory detection of Zika virus is carried out by reverse transcriptase polymerized chain reaction (RT-PCR). Virus is detectable in the blood within the first week of illness but is present for a relatively short time (3-7 days). Virus may also be detected in saliva and urine within 3-5 days after onset of illness. Zika virus may be present in urine for 20 days or longer, and virus has also been detected in semen. Zika virus infection may also be identified by serological tests, which include IgM and neutralization antibody assays. Because of potential serological cross reactions, antibody assays against dengue and chikungunya viruses should be carried out concurrently. Laboratory tests are available at the US Centers for Disease Control, at the Pan American Health Organization/World Health Organization, and at certain US state health departments. Commercial laboratory tests for Zika infection are not currently available.

Can the virus be treated?

Antivirals or vaccines against Zika virus are not currently available. Therefore, therapy of acute infection is primarily supportive. Rest, hydration, antipyretics and analgesics can be employed. If fever is treated, acetaminophen should be used. Aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) should not be used until dengue is ruled out to avoid the risk of hemorrhage.

How to prevent infection

Prevention of Zika infection is directed primarily at avoidance of mosquito bites, including wearing long sleeves and pants, applying insect repellent, and reduction of contact with mosquitos by appropriate use of screens, windows and mosquito nets.

The CDC and the European Centre for Disease Protection and Control have issued guidelines for pregnant women during Zika virus outbreaks. These include consideration of postponing travel to areas of Zika virus transmission. Pregnant women who have a travel history to areas of Zika virus transmission and who have had two or more symptoms of Zika infection should have laboratory tests performed, as should pregnant women with such travel histories who have ultrasound signs of microcephaly or intracranial calcifications.


Elsevier Connect Contributor

Raphael Dolin, MDDr. Raphael Dolin is one of the world’s leading experts on retroviral infections. He serves as Maxwell Finland Professor of Medicine, Microbiology and Molecular Genetics and Dean for Academic and Clinical Programs at Harvard Medical School. He has authored more than 200 articles, books, chapters, and reviews, and his major research focus is in the development and clinical study of candidate HIV vaccines. As one of the world’s leading experts on infectious disease, he is the lead editor for AIDS Therapy, 3rd Edition and an editor of the 8th edition of Mandell, Douglas, and Bennett’s Principles & Practice of Infectious Diseases.

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