Global Health Experts Warn Zika Could Spread Beyond Americas video player.

NEW YORK - To date, 25 countries have reported locally-transmitted cases of Zika  — a virus spread through mosquito bites with no known vaccine. The World Health Organization (WHO) has yet to declare the virus a public health emergency, although its director-general, Dr. Margaret Chan said it is spreading “explosively” across the Americas.

The virus has been linked to a medical condition known as microcephaly, a disabling birth defect in which babies are born with abnormally small heads and underdeveloped brains. In many cases, the babies do not survive.

VOA spoke with Dr. Beth Bell of the Center for Disease Control and Prevention (CDC) to clarify what we know so far about the virus and its potential effects on the world’s population.

Very large outbreak

Zika, first identified in Brazil last May, began spreading across the Americas over the last six months with “a very large outbreak,” according to Bell. The WHO has said that as many as four million people could be infected this year in the Americas alone.

Dr. Bell said most people who are infected with Zika have no symptoms. Only one-in-five experience mild symptoms, including flu, headache, fever, and rash. This has prompted an increase in health screenings and a CDC-issued travel advisory to affected countries, particularly among pregnant women at risk of passing the virus to their children.

At this point, Bell said there are more questions than answers. “We’re doing everything we can to understand a little bit more about many of the basics: How often does it happen? What are the risk factors? Are there certain things that make this transmission from pregnant women to babies more likely?”

FILE - Pietro Rafael, who has microcephaly, reacts
Pietro Rafael, who has microcephaly, reacts to stimulus during an evaluation session with a physiotherapist in Recife, Brazil, Jan. 28, 2016.

Based on other infectious causes of congenital malformations and available information on fetal brain development, Bell said the first trimester is likely the highest-risk period during pregnancy.

Potential spread to Africa, Asia

Zika has been identified in many parts of Africa and Asia in past decades, according to Bell, but never in the form of a large outbreak. She said it is possible that other regions outside of the Americas could be at risk.  

“These kind of mosquito-borne viruses, unfortunately, they have this capacity for very rapid spread, and there are some modern day factors — urbanization, large cities, international travel that tend to promote this sort of spread,” said Bell.

Already, the Pan American Health Health Organization (PAHO) has reported cases in two countries outside the Americas: Samoa and Cape Verde.

Bell said microbes are always surprising the global health community. "This is, of course, a reason for us as a global community to improve our ability to detect new infections as they emerge, and to be able to quickly identify clusters so that we can begin preventive measures early on.”

Municipal workers wait before spraying insecticide
Municipal workers wait before spraying insecticide at Sambodrome in Rio de Janeiro, Brazil, Jan. 26, 2016.

Global health preparedness

The CDC, according to Bell, has been working closely with health partners in Brazil and across the Americas, including PAHO.

“We’ve been helping the Brazilians and other countries in South and Central America with laboratory testing," she said. "This, of course, is a very important component of being able to detect and respond, is having the laboratory capacity to be able to diagnose.”

The CDC is working to better understand the association between Zika virus and microcephaly, in addition to another condition called “Guillain-Barre” syndrome — a neurological condition causing temporary paralysis — which  Bell said has been associated with a number of other infections. The National Institute of Neurological Disorders and Stroke (NINDS) says the disorder is not contagious. Most individuals fully recover from infection, although it can be life-threatening in extreme cases.

A government campaign poster informing about Zika
A government campaign poster informing about Zika virus symptoms is seen at the maternity ward of a hospital in Guatemala City, Guatemala, Jan. 28, 2016.

Key to prevention

Zika virus is spread from the same mosquito, called “Aedes,” that is known to cause Dengue fever and chikungunya virus. They live both indoors and outside, and can breed in very small amounts of water.

Bell noted that global efforts to reduce Dengue have been challenging, with little success. As such, she said the number one prevention technique is mosquito control.

“There are some things that we can do, and are done to reduce breeding sites for these mosquitoes and some application of insecticides," she said. "But it’s unfortunate that vector control is not a solution to these mosquito-borne infections.”

In addition, certain basic precautions can be taken to prevent mosquito bites, including the use of long-sleeved clothing and Environmental Protection Agency-approved repellents.

For more useful tips on how to prevent the spread of Zika, VOA has compiled a comprehensive list, which you can view here.