Claims may overstate Zika virus link to microcephaly

Brazil’s government is considering tightening the guidelines it currently gives doctors, hospitals, and health care providers for when to report infants born with abnormally small heads, a move intended to reduce the number of false alarms that it has received in wake of the Zika epidemic gripping Brazil.
In the last few months, the nation has been grappling with a growing surge in medical reports of microcephaly, a rare condition in which babies are born with unusually small heads. According to data released this week by the Ministry of Health, there have been 4,783 reported cases since October last year.
Before that, the nation had about 150 annually. But how many of the babies actually have microcephaly — and whether the condition was caused by the Zika virus — is still far from clear.
Of the 3,670 reported cases examined so far, 404 have been confirmed as having microcephaly.
Only 17 of them tested positive for the Zika virus. But the government and many researchers say that number may be largely irrelevant, because their tests would find the presence of the virus in only a tiny percentage of cases.
Another 709 babies have been ruled out as having microcephaly, according to the government, underscoring the risks of false positives making the epidemic appear larger than it actually is.
The remaining 3,670 cases are still being investigated. In a recorded message to the nation that was broadcast on Wednesday night, President Dilma Rousseff said “each federal public official has to transform into a combatant against the mosquito and its reproduction.”
As is often the case with global health epidemics, the numbers have caused confusion. Some have wondered if Brazil was overstating the extent of its health crisis.
But several independent experts said that many of the false positives were the result of an appropriate amount of caution and care by the Brazilian authorities.
The government began requiring local health officials to report suspected cases of microcephaly in October. It did so after doctors in Zika-stricken areas began seeing an alarming increase in babies being born with unusually small heads and the brain damage that often comes with it. Brazilian researchers then linked the condition to the virus, which had only recently made its way to Brazil.
The government originally told health professionals to report suspected microcephaly cases when a baby’s head at birth was 33 centimeters, or 13 inches, or less. At that time, very little was known about the virus and its possible effects on pregnancy, so officials here did what is common in public health surveillance cases: They set broad criteria to make sure they were catching as many cases as possible.
But that standard also meant that there were many false positives of babies being reported who were actually healthy, said Claudio Maierovitch, director of the department of surveillance of communicable diseases at Brazil’s health ministry.
“The protocol was initiated in October, when we had many doubts about what we were investigating,” he said. Several experts agreed with the decision.
“In the beginning of an epidemic, it is better to have a sensitive parameter and include a lot of false positives,” said Dr. Celina Turchi, an infectious disease specialist and epidemiologist in the state of Pernambuco. “Too much sensitivity and too many false positives is the way to go when you don’t know what’s going on.”
The government then changed the threshold to 32 centimeters in December, after concluding that there were many babies with small heads but without problems, Dr. Maierovitch noted.
But even after introducing the stricter standards, the number of reported microcephaly cases continued to climb rapidly.
Now, the nation’s Ministry of Health is discussing lowering the limit for head circumference for newborns again — to 31.9 centimeters for boys and 31.5 centimeters for girls — after a recommendation by medical groups that the agency met with in Brasília last week.
Maria Teresa Vieira Sanseverino, a pediatrician and medical geneticist who attended the meeting, said that, “there was consensus among the medical groups that the current criteria is too broad and is drawing too many false positives.”
One consequence of the new standard could be a significant drop in the number of reported cases.
The alarming rise in microcephaly and possible link to the Zika virus reached new importance this week when the World Health Organization declared the situation an international health emergency. It warned that as many as four million people in the Americas could be infected.
Dr. Arthur Reingold, the head of epidemiology at the School of Public Health at the University of California, Berkeley, said that Brazil is taking a “perfectly reasonable approach.”
Dr. Lavinia Schuler Faccini, president of Brazilian Society of Medical Genetics, was among those who pushed to change the head circumference to 32 centimeters in December. She also supports the new criteria being discussed.
Still, she does not fault the original protocol, saying that the Ministry did what it should have done in such matters.
Otherwise, she said, “We’d be wondering, ‘have we lost some children?’ ”

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