A Municipal Worker Gestures During An Operation To Combat The Aedes Aegypti Mosquitoes That Transmits The Zika Virus In Recife, Pernambuco State, Brazil, Tuesday, Jan. 26, 2016. Brazil's Health Minister Marcelo Castro Said That Nearly 220,000 Members Of Brazil's Armed Forces Would Go Door-To-Door To Help In Mosquito Eradication Efforts Ahead Of The Country's Carnival Celebrations. (Ap Photo/Felipe Dana)


The Zika virus is taking center stage – today officials from the WHO said that the Zika virus is “spreading explosively” in the Americas and announced that they would convene an emergency meeting on Monday to decide whether to declare a public health emergency. “The level of alarm is extremely high,” said Margaret Chan, the director general of the W.H.O., in a speech in Geneva.

Brazil’s top health official acknowledged that the country was “badly losing the battle” against mosquito-borne diseases like Zika. The country is deploying over 220,000 troops to go door-to-door handing out pamphlets about the illness.

Zika has only arrived in Brazil recently and is rapidly spreading to other parts of Latin America. More than 3,800 infants in Brazil have recently been found to have microcephaly, a previously rare condition linked to Zika in which babies are born with brain damage and abnormally small heads.

What is Zika Virus?

The Zika virus is a mosquito-transmitted infection related to dengue, yellow fever and West Nile virus. Although it was discovered in the Zika forest in Uganda in 1947 and is common in Africa and Asia, it did not begin spreading widely in the Western Hemisphere until last May, when an outbreak occurred in Brazil.

Until now, almost no one on this side of the world had been infected. Few of us have immune defenses against the virus, so it is spreading rapidly. Millions of people in tropical regions of the Americas may have had it.

How is the virus spread?

Yellow Fever MosquitoZika is spread by mosquitoes of the Aedes species, which can breed in a pool of water as small as a bottle cap and usually bite during the day. The aggressive yellow fever mosquito, Aedes aegypti, has spread most Zika cases, but that mosquito is common in the United States only in Florida, along the Gulf Coast, and in Hawaii – although it has been found as far north as Washington in hot weather.

The Asian tiger mosquito, Aedes albopictus, is also known to transmit the virus, but it is not clear how efficiently. That mosquito ranges as far north as New York and Chicago in summer.

Although the virus is normally spread by mosquitoes, there has been one report of possible spread through blood transfusion and one of possible spread through sex. The virus was found on one occasion in semen.

How does Zika cause brain damage in infants?

Scientists do not fully understand the connection. The possibility that the Zika virus causes microcephaly – unusually small heads and damaged brains – emerged in October, when doctors in northern Brazil noticed a surge in babies with the condition.

It may be that other factors, such as simultaneous infection with other viruses, are contributing to the rise; investigators may even find that Zika virus is not the main cause, although right now circumstantial evidence strongly suggests that it is.

It is not known how common microcephaly has become in Brazil’s outbreak. About three million babies are born in Brazil each year. Normally, about 150 cases of microcephaly are reported, and Brazil says it is investigating nearly 4,000 cases.

Is there a treatment?

No.  The C.D.C. does not recommend a particular antiviral medication for people infected with the Zika virus. The symptoms are mild – when they appear at all – and usually require only rest, nourishment and other supportive care.

Until recently, Zika was not considered a major threat because its symptoms are relatively mild. Only one of five people infected with the virus develop symptoms, which can include fever, rash, joint pain and red eyes. Those infected usually do not have to be hospitalized.

There is no widely available test for Zika infection. Because is closely related to dengue and yellow fever, it may cross-react with antibody tests for those viruses. To detect Zika, a blood or tissue sample from the first week in the infection must be sent to an advanced laboratory so the virus can be detected through sophisticated molecular testing.

What countries should pregnant women avoid?

About two dozen destinations in the Caribbean, Central America and South America.  The Pan American Health Organization believes that the virus will spread locally in every country in the Americas except Canada and Chile. Here is the C.D.C.’s current list of countries and territories in which Zika virus is circulating. The latest updates are here.

The Caribbean

Puerto Rico

United States Virgin Islands

Dominican Republic
Saint Martin

South America

French Guiana

Central America

El Salvador


Cape Verde
American Samoa