The good news, however, is that MERS historically hasn't spread far beyond hospitals and the households of those who are ill. One study tracked 26 MERS patients and found they only gave the virus to 4 percent of their household contacts. Another study found that the reproductive rate of MERS outside of hospitals was less than 1 — in other words, for every case that appears in the wider world, fewer than one other person catches it, on average.