Science Policy For All

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Zika and Ebola: two different viruses with shared lessons

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By: Rachel Zamoiski, Ph.D., MPH

Photo source: An Ebola isolation unit via

Zika virus has been all over the news lately, but it hasn’t been that long since a different virus was making headlines all over the world: Ebola. The Ebola epidemic of Western Africa, which began in 2014 and ended in January 2016, has resulted in over 28,000 Ebola diagnoses and over 11,000 deaths. While the seemingly near-constant news updates on Zika may remind us of the media coverage of Ebola, the two diseases are very different from each other. However, there are still lessons to be learned from the Ebola outbreak that can be applied to how we deal with this potential Zika epidemic.

The illnesses caused by Ebola and Zika are very different from each other. With Ebola, the main concern is the disease itself. Ebola is often fatal, especially in settings without good infrastructure or advanced medicine. The symptoms of Ebola are severe and can involve severe vomiting and diarrhea, as well as uncontrolled bleeding. Ebola is transmitted by contact with the body fluids of an infected person, even after the patient has died. In contrast, the symptoms of Zika are mild. It’s uncertain exactly how Zika is spread, but the primary route of transmission of Zika appears to be via mosquitoes and not direct contact with infected individuals, although other routes of transmission may be possible, as limited reports have emerged of sexual transmission. In addition, recent reports state that scientists have found active virus in saliva and urine, although it is not known if those fluids could transmit the virus. The actual symptoms caused by Zika virus is not particularly concerning when compared to Ebola. While the symptoms of the disease caused by Ebola and its high case-fatality rate were the main concerns of the Ebola outbreak, the greatest concern with Zika is the possible effect on fetuses when pregnant women are infected.

An article in Morbidity and Mortality Weekly Report from January 29, 2016 describes a “possible association” between Zika and microcephaly in babies born to mothers infected during pregnancy. The authors report an increase in cases of microcephaly, defined as a head circumference greater than two standard deviations below the mean, adjusted for gestational age and sex. The babies with microcephaly were born to mothers who either lived in or had visited areas with current Zika outbreaks. The article states that pregnant women should try to avoid contact with mosquitoes, while also noting that “further studies are needed to confirm the association of microcephaly with Zika virus infection.” While the link between Zika and microcephaly is still not well understood, it still seems prudent to advise pregnant women to avoid contact with the virus, out of an abundance of caution.

While it is important to be cautious and not expose people to unnecessary risk, even when the risk is uncertain, it’s also true that an overabundance of caution is not always a good idea. With Ebola, there were efforts to quarantine health workers returning from West Africa even when they posed no threat to public health. These efforts were made largely by politicians, and not by people with medical or scientific expertise, who instead recommended routine monitoring but not quarantine in asymptomatic individuals, as patients needed to be symptomatic in order to transmit the virus to others. This is in contrast with the well-known case of Typhoid Mary, a woman working as a cook who was forcibly quarantined because she was infecting people with typhoid even though she was not sick herself, and was unwilling to stop working as a cook. In situations like that of Ebola, not only does forced quarantine punish people for performing work that should be celebrated and honored, but it also potentially discourages healthcare workers from traveling to disease-ridden areas by stigmatizing them and treating them like prisoners unwelcome in their own country.

Less is known about Zika than about Ebola. With Zika, we don’t really know how infectious it is, or exactly how it’s transmitted. But what lessons are there to be learned from Ebola, to guide our response to Zika?

It’s important to take emerging infectious diseases seriously. One of the downsides of having such effective vaccines against formerly-common illnesses like measles and mumps is that we can forget how powerful and widespread viruses can be. The Ebola outbreak reminded us that viruses still have the potential to infect and kill many thousands of people, both far away and close to home.

Included in the threat of infectious diseases is the widespread fear caused by the perception of a seemingly unstoppable deadly virus. This understandably scared many people and undoubtedly contributed to the unscientific overreaction by many politicians. This underscores the need for good communication in the management and control of infectious diseases. If a politician announced plans to forcibly quarantine cancer patients, there would be widespread outcry and ridicule, because the general public understands cancer well enough to know that quarantine is not an effective method of preventing cancer. The same should be true for new public health concerns as well.

Finally, good data are paramount in understanding and implementing effective methods to prevent and disrupt transmission. Our efforts should focus on collecting good data, clarifying the risks of Zika, and better understanding how it is transmitted, as well as how it’s not transmitted.

With Zika, we should be cautious, and take precautions to avoid the virus even when we don’t fully understand its effects. At the same time, our response to this public health crisis, as well as others in the future, should be based on good data, and not politics or scare tactics.


Written by sciencepolicyforall

February 17, 2016 at 9:00 am

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