“Although there is no absolute proof that the Zika virus is behind the surge in microcephaly in Brazil and outbreaks of Guillain-Barré syndrome in six countries, the world’s leading health authorities are close to certain that it is,” The New York Times writes.
Unfortunately, many rumors blaming other potential causes for the spread of this virus has arisen. In a recent piece, The New York Times takes a look at the most prominent theories making the rounds on social media, along with responses from scientists:
1. Are genetically modified mosquitoes the real cause of the birth defects?
That buzzing sound you hear is a ‘no.’
A British company, Oxitec, released genetically engineered mosquitoes in Brazil in an attempt to control dengue fever. But the later microcephaly outbreaks were far away. For example, the largest mosquito release was in Piracicaba, which is 1,700 miles from Recife, where microcephaly was most common. The mosquitoes have also been released in the Cayman Islands, Malaysia and Panama without causing problems.
Mosquitoes fly less than a mile in their lifetimes. Also, only male mosquitoes were released. They do not bite humans or spread disease, and were genetically programmed to die quickly.
2. Could a larvicide in drinking water be causing microcephaly?
Entomologists have dismissed as “ridiculous” the idea that the larvicide pyriproxyfen could have caused such a large wave of birth defects. It does not attack nerve cells; it is a chemical mimic of an insect hormone that signals larvae to stop growing, and insect hormones do not endanger humans.
Pyriproxyfen was approved in the United States in 2001 and is sold as a flea treatment for dogs and cats and as a flea-killing carpet spray. Babies have crawled in the stuff for years without apparent harm. And in Brazil and Polynesia, brain damage has occurred to infants in many communities where the larvicide is not used.
3. Are vaccines to blame?
It’s not plausible.
Rumors have blamed both a “bad batch of rubella vaccine” and the introduction of a new pertussis vaccine in Brazil, or aluminum in that vaccine. Neither is plausible.
There was no rubella outbreak among pregnant women and no evidence of a “bad batch.” No vaccine is used only in northeast Brazil. The new pertussis vaccine has been used since the 1990s in many countries, including the United States. It was introduced because an older one caused soreness, fever and, in rare cases, seizures. Neither ever caused microcephaly.
4. What if another disease is causing microcephaly and Guillain-Barré?
Mounting evidence points to Zika.
The outbreak of microcephaly began in northeastern Brazilian cities where doctors had already seen thousands of people with “doença misteriosa” — the mystery disease — which was later proved to be caused by the Zika virus. Although there is no rapid test for Zika, the symptoms are easily recognized — a rash, bloodshot eyes, fever and joint pain, in large numbers of patients who are almost never dangerously ill.
Although they initially misdiagnosed it, Brazilian doctors knew for months that they had a large outbreak of an unusual disease on their hands. The same thing happened on Yap Island in Micronesia in 2007 and in French Polynesia in 2013.
Within weeks after the “mystery disease” appeared, doctors began noticing an uptick in adult paralysis — Guillain-Barré syndrome, an auto-immune disease that can be triggered by viral infections. There was a similar surge in cases in French Polynesia in 2013, and cases are now surging in Colombia, El Salvador, Suriname, Venezuela and Martinique — always in step with Zika outbreaks. In some cases, Zika virus has been found in the blood or urine of the victims.
About a year after the outbreak began in northeast Brazil, cases of microcephaly began appearing among newborns there. Pathologists in Brazil, the United States and Europe have now found Zika virus in brain tissue from stillborn and aborted microcephalic fetuses and in the amniotic fluid surrounding them.
5. Couldn’t Brazil just have been undercounting microcephaly for years?
It’s possible, but not by large enough margins to explain the current outbreak.
Some researchers believe that Brazil previously did undercount cases, but not by huge margins. Definitions of microcephaly vary, but European and North American countries report about one case per 5,000 live births to one per 10,000. Before its Zika outbreak, Brazil reported about one case per 20,000 live births — in other words, half or a quarter as many as it might really have had.
Before the outbreak, the seven states in tropical northeast Brazil where microcephaly first appeared reported about 40 cases of microcephaly a year. In October, neurologists in Recife, who normally saw microcephalic babies very rarely, found themselves treating five or more at a time. By Nov. 17, just those seven states had 400 reported cases. A month later, just one of them, Pernambuco, reported more than 600.
Eventually, the Brazilian health ministry decided that doctors were overreporting cases, so in December, it tightened its definition to include only children with heads less than 32 centimeters in circumference instead of 33. But cases continued to grow. Even previous undercounting would not explain the tremendous surge that followed Zika’s appearance.
6. Do rumors like these usually arise at the beginnings of epidemics?
“Rumors are the lifeblood of any epidemic,” said Dr. Howard Markel, a medical historian at the University of Michigan.
He gave numerous examples: In the Middle Ages, the plague was blamed on Jews, who were accused of poisoning wells. When plague erupted in San Francisco’s Chinatown in 1900, local officials blamed “rice diets.” An 1892 cholera outbreak in New York was blamed on tainted fish.
In the early days of AIDS, rumors persisted for years that it was not due to a virus, but a “gay lifestyle disease,” and that the immune system was broken down by a combination of sexual promiscuity and drugs like amyl nitrate in men exhausted by disco dancing. When AIDS was found to also be widespread in Africa, the same “denialists” blamed it on a combination of chronic fevers, weight loss, diarrhea and tuberculosis.
Why do the rumors spread so effectively?
There are three reasons.
First, Dr. Markel said, because many contain kernels of truth. Genetically modified mosquitoes were released in Brazil and larvicide was used in some cities.
Second, because many rumors have a convenient scapegoat. Diseases were once blamed on ethnic groups. Now corporations are suspect. The pyriproxyfen in Brazil was made by Sumitomo, a Japanese chemical company, and rumors about it emphasized Sumitomo’s previous partnership with Monsanto, an American company regarded with suspicion by many environmentalists.
Third, because some rumors are spread by prominent people. The larvicide rumor was begun by a group calling itself the “Doctors from the Crop-Sprayed Towns.” Among the most outspoken AIDS denialists were Peter H. Duesberg, a prize-winning molecular biologist, and Thabo Mbeki, who adopted Dr. Duesberg’s views while president of South Africa.