Here's the latest information you need to know about the Zika virus based on new reports by health officials.


The Virus Is "Spreading Explosively"

The virus has been rapidly spreading across the Americas since early last year, the World Health Organization said today. WHO Director General Dr. Margaret Chan said she was "deeply concerned" about the increase of Zika virus cases.

A Vaccine for the Virus

Dr. Anthony Faucci, the director for National Institute for Allergy and Infectious Disease, told ABC News that based on past experience with similar viruses, it may be possible for health officials to start testing a vaccine for the Zika virus later this year. The test would determine if the vaccine "is safe and effective," he noted.

Approval of a vaccine that could be readily available would likely take years, he said, and he advised Americans not to panic. A major outbreak is unlikely to happen in the U.S. because of surveillance and mosquito control methods, he said.

"Having a major outbreak like they are having in Brazil is not something that we think is likely but we are going to be very vigilant about it," Faucci said.

Where Is the Zika Virus Outbreak Happening?

The virus has been reported in Africa, South Asia and Polynesia but now it's also being found in Central and South America.

An outbreak of the disease in Brazil lead to an alert by the Pan American Health Organization last May. The U.S. Centers for Disease Control and Prevention have issued a travel alert for 24 countries and territories where the virus transmission is ongoing.

Those countries and territories are: Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela, Puerto Rico, U.S. Virgin Islands, Dominican Republic, Barbados, Bolivia, Ecuador, Guadeloupe, Saint Martin, Guyana, Cape Verde and Samoa.

What Does the Virus Do?

Common symptoms of the Zika virus include fever, rash, joint pain and conjunctivitis, according to the CDC. Approximately one in five people infected with the virus show symptoms. Severe complications from the virus that require hospitalization are rare, according to the CDC.

The virus has also been associated with a rise of microcephaly birth defect cases. The birth defect is characterized by a malformed or smaller head and brain and can result in serious developmental delays.

The CDC is also investigating if a rare paralysis syndrome called Guillain-Barre is related to the virus. The syndrome is an immunological reaction that can also occur after other viral or bacterial infections.

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ABC News gave questions to health experts, giving more detail about the Zika Virus. 

Given that only 1 in 5 people who are infected with the virus show symptoms, what threat do you see in this with regard to transmission? And what can we do, if anything, to curb the threat?

"…it will be very difficult to track the course of this virus infection without active surveillance of both mosquitoes and people. It also means we need to assume that the virus could spread across the Caribbean and even the gulf coast and take appropriate measures...I think the poorer areas of the gulf coast, including Houston are vulnerable and we need to undertake public health preparedness in the region." -- Dr. Peter Hotez, Dean of The National School of Tropical Medicine at Baylor College of Medicine

" We don't know what level of Zika virus in blood is necessary for transmission, nor do we know if the level of Zika virus in the blood is correlated to symptoms…the best way to prevent Zika now is to prevent mosquito bites. Unfortunately, large-scale vector control methods are short-lived and very expensive to maintain." - Dr. Anna Durbin, Associate Professor, Department of International Health, Johns Hopkins Bloomberg Public Health School

What, in your view, should be done to safeguard the blood and organ supply from Zika?

"Zika almost certainly will appear in the blood supply. It is possible that flavivirus screens used to detect West Nile and dengue in blood can also detect Zika. This must be pursued aggressively." -- Dr. Scott Halstead, Pediatric Dengue Vaccine Initiative, Rockville, Maryland, USA

"This virus has a short incubation period and time of infectivity, it is believed. The obvious strategy is to prevent anyone who has traveled to S and Central America to prevent blood or organ donation for a defined period, say 1 month. Alternatively, molecular testing can be pursued for extra safety, but testing is still limited to the CDC without a yet easily implemented test to use more extensively." -- Dr. Paul Auwaerter, Clinical Director, Division of Infectious Diseases, Johns Hopkins Medical

"Given that 80% of infected individuals don't realize it, people who have recently spent time in countries with ongoing Zika transmission should be excluded from donating AND the blood supply should be tested.  The same is true for tissue donations." – Dr. Dawn Wesson, Associate Professor of Tropical Medicine, President of the Louisiana Mosquito Control Association, Tulane University School of Medicine

What should people be doing – primarily pregnant women in the U.S. – in order to stay safe, aside from abiding the current travel advisory from the CDC?

"At this point the safest thing for pregnant women, or women who could be pregnant, to do is avoid or delay non-critical travel to the designated risk areas. It's very important to consult with one's obstetrician or a travel medicine specialist to assess individual risk and determine precautions that need to be taken." - Dr. Luis Ostrosky, Infectious Disease Specialist, Memorial Hermann-Texas Medical Center and McGovern Medical School at UT Health

"This is the main approach, don't travel. The issue will be a bit more difficult if/when ZV lands in South FL or the Gulf states. Then lacking any new intervention it is mosquito avoidance." - Dr. Paul Auwaerter, Clinical Director, Division of Infectious Diseases, Johns Hopkins Medical

"Transmission, when it occurs on the mainland US, is most likely to occur during the summer months…Hawaii is a different story, given that there is an ongoing dengue outbreak there, involving the same mosquitoes that transmit Zika, and of course, Puerto Rico already has Zika transmission…use of personal protection is what I would recommend for pregnant women, and anyone else who wants to avoid being bitten by the mosquitoes. Staying educated regarding presence of the virus in their area is also important…Most of the US will probably not see Zika transmission this year, but there is definite potential for introduction." – Dr. Dawn Wesson, Associate Professor of Tropical Medicine, President of the Louisiana Mosquito Control Association, Tulane University School of Medicine