The Zika virus, blamed for a surge in birth defects, is "spreading explosively", World Health Organization chief Margaret Chan said Thursday, calling for an emergency meeting on the outbreak on February 1.
"The level of alarm is extremely high," Chan told a meeting of WHO member states in Geneva, calling for a February 1 meeting to determine if the outbreak qualifies as an international public health emergency.
The virus "is now spreading explosively," she added.
Chan said that during previous outbreaks the virus, which was first discovered in a monkey in Uganda in 1947, "occasionally caused a mild disease of low concern."
But "the situation today is dramatically different," she said, highlighting the growing concern that Zika has links to a birth defect known as microcephaly, or an abnormally small head.
"A causal relationship between Zika virus infection and birth malformations and neurological syndromes has not yet been established, but is strongly suspected," Chan said.
She explained that the February 1 Emergency Committee meeting will seek "advice on the appropriate level of international concern and for recommended measures that should be undertaken in affected countries and elsewhere."
The Zika virus is strongly suspected of causing birth defects and may infect 3-4 million people in the Americas, including 1.5 million in Brazil, World Health Organization expert Marcos Espinal, who heads WHO's Americas arm, told the conference.
He said a study would soon be published suggesting a correlation between Zika and microcephaly -- babies born with small heads and brains -- in Brazil.
"We don't know yet if this virus crosses the placenta and generates or causes microcephaly. We think it plays a role. There's no doubt about that," he told the WHO's executive board meeting in Geneva.
Earlier this week officials in Rio ramped up their fight against the mosquitoes that spread Zika, dispatching a team of fumigators to the Sambadrome, where the city's Carnival parades will take place next month. There is no specific treatment or vaccine for Zika, which is related to dengue — scientists have struggled for years to develop a dengue vaccine but have failed to create an effective shot so far.
WHO will convene an emergency committee on Monday to decide if the Zika virus outbreak should be declared an international health emergency.
Chan said although there was no definitive proof that the Zika virus was responsible for a spike in the number of babies being born with abnormally small heads in Brazil, "the level of alarm is extremely high."
She also noted a possible relationship between Zika infection and Guillain-Barre syndrome, which can cause temporary paralysis.
"The possible links, only recently suspected, have rapidly changed the risk profile of Zika from a mild threat to one of alarming proportions," Chan said.
According to the U.S. Centers for Disease Control, the Zika virus is now in more than 20 countries, mostly in Central and South America.
Chan cited four main reasons why WHO is "deeply concerned" about Zika: The possible link to birth defects and brain syndromes, the prospect of further spread, a lack of immunity in populations in the newly affected areas and the absence of vaccines, treatments or quick diagnostic tests for the virus.
Still, convening an emergency committee does not guarantee that a global emergency will be declared — WHO has held 10 such meetings to assess the Middle Eastern respiratory syndrome coronavirus and no emergency has been announced.
Declaring a global emergency is akin to an international SOS signal and usually brings more money and action to address an outbreak. The last such emergency was announced over the 2014 devastating Ebola outbreak in West Africa; polio was declared a similar emergency the year before.
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