Posted: May 6, 2016

Conspiracy theories could hamper control of Zika.

Cartoon of person with microscopeIn Brazil, Zika virus is being investigated as a potential cause of nearly 4,000 cases of newborn microcephaly, a condition in which the brain fails to fully develop. Currently, the virus is found mostly in South and Central America, Mexico, and the Caribbean, but it is spreading rapidly and could infect up to four million people by the end of 2016, according to the U.S. Centers for Disease Control and Prevention.

Given the speed of its spread, it's not surprising that people are scared, even though most of the world has little to worry about at the present time. For example, so far, no local transmissions of the virus have occurred in the United States; in other words, Americans currently are extremely unlikely to contract the virus while on home soil. Most of the approximately 100 people who have been diagnosed in the U.S. were infected while traveling to affected countries. A few of them have contracted the virus through sexual transmission.

Despite the current low risk, people are afraid, and when people are afraid, misinformation can spread like wildfire. Already conspiracy theorists are infiltrating the conversation about the rising incidences of microcephaly, claiming that it's caused by insecticides in public water systems or genetically modified (GM) mosquitoes. These conspiracy theories spur confusion, and worse, may damage efforts to protect people from Zika.

For example, genetically modified Aedes aegypti mosquitoes, which have been released in Brazil for the past several years, have suppressed local mosquito populations and reduced their ability to sustain dengue virus transmission. The GM mosquito conspiracy theory regarding Zika virus posits that the piggyBac transposon--which is used to genetically modify mosquitoes--is transferred into the Zika virus genome, which carries the transposon to the developing human fetal brain during gestation, causing microcephaly.

This theory ignores the indisputable fact that piggyBac is a DNA transposon, which only can be inserted into DNA. Zika has an RNA genome, which is completely incompatible with the piggyBac transposon. In addition, the GM mosquitoes that have been released in Brazil are nowhere near the location of the initial Zika outbreak. Halting use of GM mosquitoes will lead to significantly more disease-harboring mosquitoes and more deaths from dengue virus and other illnesses.

The insecticide conspiracy theory suggests that the treatment of drinking water with the insect juvenile hormone analogue pyriproxyfen is the true cause of microcephaly. There is no plausible rationale for this theory. Pyriproxyfen--which suppresses larval development or adult emergence from the larval stage--acts on hormonal insect growth pathways that are not present in humans or any other vertebrate. On top of that, a person would have to consume thousands of gallons of treated drinking water per day to even approach toxic levels, and the effects would have nothing to do with microcephaly. Despite these facts, some states in Brazil have suspended use of pyriproxyfen in drinking water, which surely will worsen the outbreak.

For now, Zika virus is not something that most Americans should worry about. Controlling this virus will rely on a rapid public health response in affected countries, proactive preparation in countries likely to see virus introductions, and education to prevent the spread of conspiracy theories that may hamper control efforts.

--Jason Rasgon, Ph.D.

Jason Rasgon is an associate professor of entomology and disease epidemiology in the Center for Infectious Disease Dynamics at Penn State.