Saudi Arabia has reported an increase in the number of people with MERS. This is not something to worry about in and of itself. An increase in reported infections does not mean more infections. It may, but it is just as likely that doctors are just looking for it more now that they know to do so. And finding out there are more people getting infected than previously observed could also show us that the mortality rate isn’t as high as the current reported rate (~1/3).
There is concern that MERS will end up behaving like SARS did and become a global epidemic. So far this hasn’t happened, in part because it doesn’t seem to transmit between people very easily and might also not actually be that deadly. With the early scrutiny being placed on MERS it is unlikely to become a problem even if it does mutate. Except for one heightened risk factor: pilgrimages. If the virus mutates to become more communicable amongst people, it will be much more difficult to control its spread with a lot of people entering and leaving Saudi. If MERS does mutate, will Saudi and other countries be willing (or even able) to put in place the same controls that helped contain SARS, especially if they would interfere with the Haj and other pilgrimages?