The letter points out that Rio is at the epicenter of the Zika epidemic, with 32,000 cases so far, and the holding the games there–with all the associated travel involved–may accelerate the spread of the dangerous Brazilian strain.

The newly emerging risk of Guillain-Barré syndrome makes it clear that Zika virus presents a threat to everyone. The Rio Olympics are likely to make it worse. Anyone planning to visit Rio for the Games should take all the precautions they can, but the best plan might be simply to stay home.

Steven Salzberg is the Bloomberg Distinguished Professor of Biomedical Engineering, Computer Science, and Biostatistics at Johns Hopkins University.