Zika causes birth defects, CDC officials confirm

Washington: Officials at the Centres for Disease Control and Prevention said Wednesday there was now enough evidence to definitively say that the Zika virus could cause unusually small heads and brain damage in infants born to infected mothers.

The conclusion should settle months of debate about the connection between the infection and these birth defects, called microcephaly, as well as other neurological abnormalities, the officials said.

“There is no longer any doubt that Zika causes microcephaly,” said Dr Thomas R. Frieden, the CDC director. He said the conclusion, reached after evaluating “mounting evidence from many studies”, signifies “an unprecedented association” in medicine.

“Never before in history has there been a situation where a bite from a mosquito can result in a devastating malformation,” Frieden said.

He and other agency officials said they hoped that the announcement increased awareness and concern about the potential threat to Americans who travel to affected areas in Latin America and those living in Puerto Rico, American Samoa and Southern states where the virus is expected to arrive this summer.

The announcement may increase pressure on Congress to allocate more than $1.8 billion (Dh6.6 billion) in emergency funding that President Barack Obama requested for prevention and treatment of the outbreak.

While CDC officials did not address funding, Dr Sonja A. Rasmussen, the agency’s director of public health information and dissemination, said the conclusion “emphasises the importance of working on ways to prevent Zika infection,” including efforts to develop a vaccine.

“Surveys have told us that a lot of people aren’t concerned about Zika virus infection in the United States — they don’t know a lot about it,” Rasmussen said.

“Now that we can be more convincing that Zika virus does cause microcephaly, we hope that people will focus on our prevention messages more closely.”

‘Good call’

The CDC analysis, led by Rasmussen, was published Wednesday in The New England Journal of Medicine, and involved weeks of research into findings that have emerged from Brazil and elsewhere, including studies involving foetuses with microcephaly in pregnant women infected with Zika.

“The important part is that the CDC can now take action without having to spend time trying to confirm the link,” said Dr Eric J. Rubin, an infectious disease expert at Harvard and an editor at The New England Journal of Medicine.

Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, said the CDC’s announcement was a “good call,” adding “I give them credit for making clear and unambiguous statements about the neurologic complications”.

About 700 people in the United States have been infected with the Zika virus as of last week, including 69 pregnant women, Dr Anne Schucat, the deputy director of the CDC, said Monday at a White House briefing. About half of the cases are in Puerto Rico, where the virus is circulating locally. Most of the other American cases have occurred in people who travelled to South America.

But Schucat said that mosquitoes that can transmit Zika are present in 30 states during the warmer months, a much larger swath of the United States than health officials initially expected.

States considered most at risk include Florida and Texas, especially in urban areas where the mosquito thrives and in neighbourhoods where lack of air conditioning means more open windows that give the insects greater access to people.

The CDC’s announcement comes two weeks after the World Health Organisation said there was “a strong scientific consensus” that Zika causes microcephaly and other neurological disorders.

Turning point

In an interview Wednesday, Dr. Bruce Aylward, head of emergency response for the WHO, called the CDC’s announcement “really responsible public health” and “a turning point in the course of this epidemic.” American officials realised “people are not taking precautions,” he said. “They are still questioning whether Zika is the cause.”

“If you are going to prevent disease, you have got to change behaviour today,” he added.

CDC officials said they were not ready to confirm that Zika can cause neurological conditions in adults, including Guillain-Barre syndrome, cases of which have increased in some countries in the Zika outbreak.

The WHO said last month that evidence substantiated the connection between the infection and Guillain-Barre syndrome. On Wednesday, CDC officials said that because the syndrome can be triggered by other infections, they were waiting for the results of studies being conducted in Brazil and elsewhere.

But the CDC was unequivocal about microcephaly. Not only can Zika cause the condition, Rasmussen said, but it also appears to cause more severe forms of it. Microcephaly caused by the Zika virus resembles a particularly destructive type called “fetal brain disruption sequence,” which includes serious problems with swallowing and bending joints. “Even just the measurements of the babies’ heads are much smaller” than in other types of microcephaly, she said.

Beyond microcephaly, Rasmussen said, the authors concluded that Zika causes some other fetal brain problems, such as calcifications inside the skull. But much remains unknown, including whether Zika harms other organs, how likely it is that women infected with Zika will have brain-damaged babies, and to what extent the risk varies according to when in pregnancy the infection occurs.

Rasmussen said other brain defects may also be linked to Zika infection. “We do expect that this is likely to be the tip of the iceberg,” she said, “that there will be babies who won’t have the small head per se, but will have other types of brain defects.”