The Zika virus is "is now spreading explosively"

New York: The Zika virus is "is now spreading explosively" in the Americas, the head of the World Health Organization said Thursday, with another official estimating between 3 million to 4 million infections in the region over a 12-month period.

"The level of concern is high, as is the level of uncertainty," Dr. Margaret Chan, WHO's director-general, told her organization's executive board members. "We need to get some answers quickly."

The lack of any immunity to Zika and the fact that mosquitoes spreading the virus can be found most "everywhere in the Americas" -- from Argentina to the Southern United States -- explains the speed of the virus' spread, said Dr. Sylvain Aldighieri, an official with the WHO and Pan American Health Organization.
Zika virus: What to know
Aldighieri gave the estimate for Zika infections (including people who do not report clinical symptoms) based on data regarding the spread of a different mosquito-borne virus -- dengue. He acknowledged the virus is circulating with "very high intensity."

Some 80% of those infected with the Zika virus never know they have it. But there are major worries about the dangers pregnant women and their babies face.

Chan said that, where the virus has arrived, there's been a corresponding "steep increase in the birth of babies with abnormally small heads and in cases of Guillain-Barre syndrome." Having small heads can cause severe developmental issues and sometimes death. Guillain-Barre is a rare autoimmune disorder that can lead to life-threatening paralysis.

Dr. Bruce Aylward, another WHO leader, cautioned that no definitive link has been established but said there's legitimate reason to be concerned.

Zika potentially poses a dire health threat to areas with millions of people, but it's far from clear what to do about it.

Pregnant women, their babies at high risk
After first being detected in 1947 in a monkey in Uganda, Zika was most often found along the equator from Africa into Asia. Nine years ago, new cases popped up in islands in the Pacific Ocean.

Last year, the virus made its way to the Americas -- with devastating results.

The number of cases there has grown exponentially, prompting public health measures aimed at curbing it and protecting those most endangered, particularly women who could become pregnant or who already are.

Brazil alone has reported more than 4,000 cases of microcephaly -- a neurological disorder resulting in the births of babies with small heads -- in infants born to women infected with Zika while pregnant.

The mosquito-borne disease is in 23 countries and territories in the Americas, according to Chan.

On Thursday, an official with the Centers for Disease Control and Prevention said 31 "travel-associated cases" of the Zika virus have been documented in 11 states and the District of Columbia this year and last, and that number will likely rise. The figure is on top of 19 laboratory-confirmed cases in Puerto Rico and one in the U.S. Virgin Islands, according to the CDC's Dr. Anne Schuchat.

As of Thursday, there were no cases of the disease being transmitted in this country. All those were contracted elsewhere in the Western Hemisphere.

Chan has called an emergency committee meeting Monday in Geneva, Switzerland, to talk about what health officials worldwide should do about the Zika virus.

U.S.-based researchers Daniel Lucey and Lawrence Gostin had called for just such a meeting this week in the Journal of the American Medical Association, criticizing the WHO for not stepping up sooner.

"The very process of convening the committee would catalyze international attention, funding, and research," Lucey and Gostin wrote in an article published Wednesday. "While Brazil, PAHO and the CDC have acted rapidly, WHO headquarters has thus far not been proactive, given potentially serious ramifications."

After Chan's announcement about next week's meeting, Gostin urged the WHO leader to "mobilize international resources to curb the rapid spread of Zika worldwide, including aggressive mosquito control, active surveillance, accelerated vaccine research and travel advisories for pregnant women."

"It is far better," said the Georgetown University public health expert, "to be overprepared than to wait until a Zika epidemic spins out of control."

With no vaccine, controlling mosquitoes is key

The Geneva meeting will aim to pull together research and get experts' recommendations on the next steps. Chan said she also wants "to prioritize areas where research is most needed."

Right now, there are no vaccines to prevent the Zika virus, which not only pregnant women but their fetuses can contract. Nor are there medicines to treat those who have it.

Officials in Colombia, Jamaica and El Salvador have advised women not get pregnant so long as the Zika threat remains. Eduardo Espinoza, El Salvador's vice minister of health, recommended that women should "plan their pregnancies and try to avoid getting pregnant this year and the next."

The WHO isn't going that far, nor does it plan to anytime soon, according to Aylward. The agency will more likely focus on advising women in the Americas who want to get pregnant to reduce their risk of mosquito bites.

Authorities are also focusing on containing the Aedes mosquito species, which spreads the disease. That type of mosquito can be found in the United States.

And the regularly occurring global weather phenomenon known as El Niño is expected to make things worse by increasing mosquito populations, Chan said.

Controlling the number of mosquitoes in any specific locale is challenging. Microbiologist Brian Foy noted that Aedes mosquitoes "can replicate in flower vases and other tiny sources of water."

This news was published on CNN.com