The World Health Organization took the unusual step

 The World Health Organization took the unusual step on Monday of declaring an international public health emergency in response to reports of clusters of brain damage in infants linked to the rapidly spreading Zika virus.
The condition, called microcephaly, develops before birth and causes small heads and brains in babies. It's considered rare, but Brazil has seen an apparent spike in cases since the mosquito-borne Zika virus was first reported in the country in May.
More than 4,000 cases of microcephaly in Brazil are believed to be related the Zika virus, according to media reports. Health officials are still in the process of doing the painstaking and slow work of verifying those cases and linking them to Zika.
So far, just 270 have been verified to be microcephaly in women who were exposed to the virus. More than 3,400 still need to be confirmed.
Experts also noticed an increase in microcephaly cases in French Polynesia during a 2014 outbreak of the Zika virus there, says David Heymann, MD, the chair of the committee of experts that advised WHO on its decision. Heymann is a professor of infectious disease at the London School of Hygiene and Tropical Medicine.
The declaration will speed up research into the connection and increase international cooperation to determine the cause of the microcephaly cases, which officially remains a mystery to scientists, though Zika is strongly suspected.
“There is an urgent need to do a lot more work,” said Margaret Chan, MD, director-general of the WHO, in a press briefing after announcing the decision. “We need a coordinated international response to make sure we get to the bottom of this.”
Importantly, Chan said she saw no need for travel or trade restrictions to affected countries. The CDC has already advised women who are pregnant or may become pregnant against travel to more than 25 nations and territories in Central and South America, and the Caribbean.
Chan said new studies to firmly establish or rule out a connection should begin within the next 2 weeks.
For the time being, she said, the most important thing to prevent the infection is to avoid mosquito bites. That’s especially important for pregnant women.
It’s only the fourth time the WHO has declared a public health emergency of international concern. The first time was in 2009, in response to the H1N1 swine flu pandemic. The second was in May 2014 because of a surge in polio cases. The third international emergency was declared in 2014 after Ebola cases exploded in West Africa.