The World Health Organization warned Thursday that the world could see an “explosive” spread of the Zika virus to up to 4 million people, further raising alarms about the mosquito-borne disease whose outbreak in Latin America is believed to be linked to severe birth defects.
Canadian Blood Services, meanwhile, will soon refuse blood donations from those who have traveled to countries where the Zika virus has become widespread. The agency’s chief medical and scientific officer said the blood-collection agency will decide in the next few days which travel destinations would be linked to a temporary ban on donating blood.
The risk of the virus being transmitted through blood transfusion is low, but Canadian Blood Services doesn't want to take any chances, the medical officer said.
Margaret Chan, the director-general of WHO, said it will hold a meeting on Monday to decide if Zika should be declared an international emergency. She added that the spread of the disease had gone from a mild threat to one of alarming proportions.
The virus “is now spreading explosively,” she said. “As of today, cases have been reported in 23 countries and territories in the [Americas] region.”
Marcos Espinal, an infectious disease expert at the WHO's Americas office, said, "We can expect 3 [million] to 4 million cases of Zika virus disease." He gave no time frame.
Meanwhile, Dr. Anne Schuchat of the U.S. Centers for Disease Control and Prevention told reporters Thursday that there have been 31 cases of Zika infection among U.S. citizens who traveled to areas affected by the virus. So far, there have been no cases of transmission of the virus through mosquitoes in the United States, she said.
Those 31 people are in 11 states and Washington, D.C. In U.S. territories, Puerto Rico has 19 confirmed cases, and the Virgin Islands has one.
The U.S. government is looking at the issue of blood donations from travelers, although officials think the virus is gone from an infected person's blood in a week or less.
Schuchat said that "any outbreaks in the continental U.S. would be limited" for a number of reasons, including the fact that urban areas in the U.S. are "not as densely populated" as in the countries where the virus has spread.
There is no vaccine or treatment for Zika, which is a close cousin of dengue and chikungunya and causes mild fever, rash and red eyes.
Brazil's Health Ministry said in November 2015 that Zika was linked to a fetal deformation known as microcephaly, in which infants are born with abnormally small heads.
An estimated 80 percent of people infected have no symptoms, making it difficult for pregnant women to know whether they have been infected.
Dr. Anthony Fauci, director of the National Institute for Allergy and Infectious Disease, said a possible vaccine was based on work done on the West Nile virus. Fauci said that vaccine was never developed because a drug company partner could not be found, but he did not see this as an issue for Zika.
"We're already talking to a few companies who are able to partner with us in advanced development," he told reporters.
Brazil has reported 3,893 suspected cases of microcephaly since October, the WHO said last week — more than 30 times the number seen in any other year since 2010.
In Venezuela, authorities on Thursday broke their silence on the Zika outbreak. Venezuelan Minister of Health Luisana Melo appeared on state television on Thursday and said health authorities there have recorded 4,700 suspected cases of Zika.