Fearful of catching the MERS virus, workers wear masks during a soccer match on April 22 at King Fahad stadium in Riyadh. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

Saudi men walk to the King Fahad hospital in the city of Hofuf on Sunday. In eastern Saudi Arabia, where outbreaks of the MERS virus have been concentrated, people have resumed their habits of shaking hands and kissing. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

A railway worker wearing protective clothing to ward off the SARS virus controls a line of travelers as they wait to enter Beijing's West Railway Station Tuesday in 2003. Greg Baker/AP hide caption

itoggle caption Greg Baker/AP