Zika Virus Outbreak Recently Recorded Across Africa, Americas, Asia and Others

Zika virus is a member of a virus family Flaviviridae. It is spread by daytime-active Aedes mosquitoes, such as A. aegypti and A. albopictus. Its name comes from the Ziika Forest of Uganda, where the virus was first isolated in 1947.

The infection, known as Zika fever or Zika virus disease, often causes no or only mild symptoms, similar to a very mild form of dengue fever. 

While there is no specific treatment, paracetamol (acetaminophen) and rest may help with the symptoms. 

As of April 2019, no vaccines have been approved for clinical use, however a number of vaccines are currently in clinical trials. 

Zika can spread from a pregnant woman to her baby. This can result in microcephaly, severe brain malformations, and other birth defects. Zika infections in adults may result rarely in Guillain–Barré syndrome.

In January 2016, the United States Centers for Disease Control and Prevention (CDC) issued travel guidance on affected countries, including the use of enhanced precautions, and guidelines for pregnant women including considering postponing travel. 

Other governments or health agencies also issued similar travel warnings, while Colombia, the Dominican Republic, Puerto Rico, Ecuador, El Salvador, and Jamaica advised women to postpone getting pregnant until more is known about the risks.

Zika outbreaks have now been recorded across Africa, the Americas, Asia and the Pacific. That includes an outbreak in French Polynesia in 2013 with thousands of suspected cases, and a large epidemic across Latin America and the Caribbean from 2015 to 2016 in which 1.5 million people were infected in Brazil alone. The increasing number of cases led to two important discoveries.

Firstly, although most people had mild symptoms like headaches, fever and joint pain, Zika infection could also cause Guillain-Barré syndrome, a rare condition that can lead to paralysis. Secondly, and most concerning, was the discovery of Zika's impact on pregnant women and their unborn babies.

How is Zika spread and what are its health impacts?

During the 2015 to 2016 epidemic, it was discovered that Zika can spread from a mother to their foetus during pregnancy. It's estimated to cause adverse outcomes for babies in 5 to 42 percent of infected pregnant women. 

That includes congenital malformations like microcephaly, where babies are born with a clinically small head, and permanent brain damage. 

In Thailand, where there were 758 reported cases of Zika in 2023, 13 babies were born with these health issues in the same year. Zika can also cause premature birth, stillbirth and foetal loss.

Zika can be transmitted in other ways too. It primarily spreads through the bite of infected Aedes mosquitoes, the same mosquitoes that spread dengue, yellow fever and chikungunya. It can also be spread by sexual contact, blood transfusion – and possibly organ transplantation.

Several factors increase the risk of the disease moving to new places. For example, rising levels of international travel and trade can cause Zika to spread beyond the tropical and subtropical regions where it is commonly found. 

Meanwhile, it’s estimated that warming temperatures as a result of the climate crisis could create more suitable environments for mosquitoes, putting 1.3 billion people at risk of Zika by 2050.

There’s also evidence that shows Zika can co-circulate in human populations with dengue, and that the viruses cause cross-reactive immune responses. 

That means an infection with one virus can affect a person’s immune response to the other. But data on how they interact, particularly in the most affected communities, is limited.