It is reasonable to estimate that there could be 3 million to 4 million cases of Zika virus in a 12-month period in the Americas, WHO official Dr. Sylvain Aldighieri said Thursday.
He cautioned that this is only an estimate, based on data regarding how a different virus — dengue — spreads, though he acknowledged the Zika virus is currently circulating with “very high intensity.”
He said the estimate covers all Zika infections, including people who might not report clinical symptoms.
The lack of any immunity to Zika virus and the fact the mosquitoes that spread it can be found most “everywhere in the Americas” — from the southern tip of Argentina to the southern United States — “explains the speed” of the Zika virus’s spread, Aldighieri said.
A WHO emergency committee meeting on the Zika virus to be convened Monday in Geneva will review evidence related to the virus and offer recommendations on curbing Zika’s spread and its possible association with neurological disorders, WHO official Dr. Bruce Aylward said.
The panel also will try to ensure that member states don’t make inappropriate steps that would unnecessarily affect travel and trade, Aylward said.
Aylward and Aldighieri were speaking to reporters in Geneva.
“The level of concern is high, as is the level of uncertainty,” WHO Director-General Dr. Margaret Chan told her organization’s executive board members. “We need to get some answers, quickly.”
The mosquito-borne disease is now in “23 countries and territories in the region,” according to Chan. The U.S. Centers for Disease Control and Prevention has said Zika is in 24 nations.
While it’s been around in some form for decades, alarms have raised only recently about Zika’s connection with “birth malformations and neurological symptoms.”
Chan explained 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, meanwhile, is a rare autoimmune disorder that can lead to life-threatening paralysis.
There’s no doubt, then, that Zika virus poses a dire health threat to areas that are home to millions of people. What is far less clear is what to do about it.
Pregnant women, their babies at high risk
After being first 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, it made its way to the Americas — with already devastating results.
The number of cases there has grown exponentially, prompting significant public health measures aimed at curbing it and protecting those most endangered by it, particularly women who could become pregnant or who already are. Brazil alone has reported more than 4,000 cases of microcephaly — a neurological disorder that results in babies being born with small heads — in infants born to women infected with Zika during their pregnancies.
Chan called an emergency committee meeting to convene February 1 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 in an article published Wednesday in the Journal of the American Medical Association, criticizing the World Health Organization for not stepping up sooner.
“The very process of convening the committee would catalyze international attention, funding, and research,” Lucey and Gostin wrote. “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 Chan to “urgently 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 meeting in Geneva 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 Zika virus, which not only pregnant women but their fetuses can contract. Nor are there medicines to treat those who have it.
Efforts now are focused on containing Aedes albopictus, or the Asian tiger mosquito, which spreads the disease.
That type of mosquito can be found in the United States, though as of Thursday there had been no cases of the disease being transmitted in the country. All of the Zika cases in the U.S. were contracted elsewhere in the Western Hemisphere.
And the regularly occurring global weather phenomenon known as El Niño is expected to make things worse by increasing mosquito populations, Chan said.
Still, 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.”