What we know so far about Zika virus

Named after Zika forrest in Uganda, where the first case was found in monkeys in 1947, Zika virus has originally remained in Africa and in few small and sporadic cases in Asia (including in Indonesia in 1977). But by 27 January 2016 the virus has spread to 23 countries, with World Health Organization (WHO) esimated that there could be 3 to 4 millions infections in the Americas this year.

As with so many outbreaks, there are plenty of rumours or misleading news spreading along with the facts, and Annalisa Merelli and Katherine Ellen Foley of Quartz give a gentle reminder that “the key is knowing what to worry about and what not to.”

So here’s what the world knows about Zika virus up until now:

• Fact: Zika virus is caused by the bite of an infected Aedes Aegypti mosquito. The bite is usually causing non life-threatening conditions in adults such as mild fever, rash, conjunctivitis, and muscle pain. Those infected usually does not have to be hospitalised.

• Unverified: However, as it has become the face of Zika virus in the media, the virus has also been associated with a sudden spike in newborn microencephaly (brain shrinkage), particularly in Brazil where last year there were 4000 babies with brain deformities. No direct link has yet to be found that they were in fact caused by Zika virus. But still, as a precaution, there are travel warnings to Latin America for women, and the government of El Salvador went as far as suggesting women to postpone pregnancy until 2018.

• Fact: At the moment Zika virus is spreading in these countries: Barbados, Bolivia, Brazil, Colombia, Dominican Republic, Ecuador, El Salvador, French Guiana, Guadeloupe, Guatemala, Guyana, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Puerto Rico, Saint Martin, Suriname, US Virgin Islands and Venezuela, where in some cases like in Brazil the virus is spreading at a worrying pace.

• Unverified: Zika virus has also been linked with the Guillain-Barré Syndrome (GBS), a rare neurological condition which starts with numbness, tingling, or pain in muscles, and it can also escalate to cause paralysis and even death. Just like the microencephaly cases, no direct link has yet to be found, but the experts are investigating it real closely.

• Unverified: There are reports that suggest Zika virus could be spread through sex. However, the reports are based on only few isolated cases (and also allegedly linked, not confirmed). But again, at this early stage scientists are not rulling anything out.

• Fact: The escalating spread of Zika virus is yet another effect of global warming, where last year’s exceptionally strong El Niño has produced above-average rainfall and flooding, which are perfect conditions for mosquito breeding.

• Unverified: In what can be a dreadful scenario, Brazilian scientists believed that Zika virus may have already cross over to the common mosquito. But no concrete evidence has been found so far.

• Fact: US scientists say vaccine is still 10 years away. True, but there is also no potent vaccine for flu either, and it does not mean that the virus is not curable. Treatment for Zika usually require rest, nourishment and other supportive care, similar like the treatment for dengue fever.


• 1 February: The WHO has declared that the microcephaly symptoms, which are strongly linked to Zika virus, as a Public Health Emergency of International Concern (PHEIC). With this state of emergency the WHO is increasing its monitoring in countries where Zika virus has been spotted, in order to determine whether the brain deformity cases are really caused by the virus. The urgency was highlighted by the director-general of WHO Margaret Chan when she said that “there is an urgent need to coordinate international efforts to understand whether the Zika virus is causing birth defect.” Note that the PHEIC is applied to microcephaly and not the Zika virus itself.

• 3 February: The first case of Zika virus spread to the United States has been identified, where a person in Texas was likely infected through sexual intercourse. This also confirms that, though it’s still quite rare, Zika virus can indeed spread through sexual transmissions.

• 4 February: Indonesia’s Health Ministry has issued a travel advisory for 8 countries hit by Zika virus: Brazil, Cape Verde, Colombia, El Salvador, Honduras, Martinique, Panama and Suriname. They also recommended citizens to avoid entering these 22 countries with “active transmission” status (including nearby Thailand): Barbados, Bolivia, Curacao, the Dominican Republic, Ecuador, Fiji, French Guiana, Guandalope, Guatemala, Guyana, Haiti, Mexico, New Caledonia, Nicaragua, Paraguay, Puerto Rico, Saint Martin, Samoa, Tonga, Thailand, the US Virgin Islands and Venezuela.

• 10 February: According to the latest data from the WHO, only 17 out of around 400 microcephaly cases in Brazil are confirmed by the Brazilian health officials as positively tested for Zika infection. In fact, as Ana Campoy of Quartz reports, “even in places not hit by the virus, kids are at risk of being born with microcephaly,” which many of those cases are caused by a virus called Cytomegalovirus (CMV). Here’s more about CMV.

• 16 February: Scientists still can’t say Zika causes microcephaly.

• 9 March: this is what we’ve all been scared of: the WHO said that, although nothing is 100% confirmed yet, but increasing evidence suggest that 1. Sexual transmission of the Zika virus is more common than previously thought 2. Zika is indeed has been causing the surge in birth defects, and 3. Also causing neurological problems.

• 9 May: scientists have developed a quick and cheap way to test for Zika.

Further readings:

Zika virus infection and Zika fever: frequently asked questions [World Health Organisation]

Centers for Disease Control and Prevention: Zika virus disease Q&A [Centers for Disease Control and Prevention]

What we need to know about Zika virus [BBC News / James Cook]

Interview with the experts: Zika, what is it and should you be worried about it? [Quartz / Annalisa Merelli and Katherine Ellen Foley]

Short answers to hard questions about Zika virus [The New York Times / Donald G. McNeil jr., Catherine st Louis and Nicholas st. Fleur]

Zika virus spreading explosively, says World Health Organization [The Guardian / Matthew Weaver]

Brazil’s surge in small-headed babies questioned by reports [Nature / Declan Butler]

Does the Zika virus cause birth defects? Remember that correlation is not causation [Wired / Lizzie Wade]

Zika virus has now been linked to Guillain-Barré Syndrome [Quartz / Akshat Rathi]

Zika virus could be spread through sex, cases suggest [Time / Tara John]

Is El Niño to blame for the “explosive” Zika virus outbreak? [Mother Jones / Tim McDonnell]

Zika virus may have spread to common mosquito [Sky News / Alex Crawford]

Conspiracy theories about Zika spread through Brazil with the virus [The New York Times / Andrew Jacobs]