More than 3,400 cases of Zika have been reported in the United States and Puerto Rico, and the number of cases is expected to climb to more than 7,000 by the end of the month, according to a government report released Tuesday.
The report said about a quarter of the cases have been linked to the Zika virus, although some people infected with the virus can be infected with other causes.
There have been several high-profile cases of babies born with birth defects linked to Zika, including a baby born with microcephaly who died last month at age 3 months.
The Centers for Disease Control and Prevention said on Tuesday that the virus is spreading in new and emerging parts of the world.
The virus is not spreading among pregnant women, although the virus was found in blood samples from women who had been pregnant and had symptoms of the virus.
The CDC said there is evidence that Zika can affect pregnant women’s ability to give birth, which is known to cause problems such as low birth weight, low birth weights, and premature labor.
The disease is not known to affect people who are already pregnant.
The latest outbreak began when an outbreak of microcefasis emerged in Brazil, the first confirmed case of the Zika strain, according the CDC.
The WHO said Wednesday that the case count in Brazil had climbed to nearly 6,500, with more than 2,000 people infected.
“The current epidemic is expected in Brazil and other areas of the Caribbean,” WHO director-general Dr. Margaret Chan said in a statement.
The virus has spread through Brazil’s densely populated northern interior, where it is causing a “serious threat to public health,” the WHO said.
In other parts of Latin America, Colombia and Peru have reported at least one case each, and Chile and Argentina have confirmed two cases.