Health experts say camels are the most likely animal source of infection for the disease, which the Saudi health ministry on Saturday said that seven more people had caught.
First reported two years ago in Saudi Arabia, MERS is a coronavirus like SARS, which originated in animals and killed about 800 people worldwide after first appearing in China in 2002. There is no vaccine against it or anti-viral treatment for it.
More than one-quarter of the 480 diagnosed with MERS in Saudi Arabia have died, while cases have been reported in other Middle Eastern countries, in Europe and in the United States, which had its first confirmed case last month.
The link between human cases and camels is the subject of extensive study among scientists abroad. But it has been relatively absent from much of the official domestic debate.
In a statement, the Agriculture Ministry advised people not to come into contact with camels unless necessary and to wash their hands before and after if they did, as well as wearing face masks.
It also advised only eating cooked camel meat and to boil camel milk before consuming it.
Public disquiet in Saudi Arabia has grown amid rumours on social media about a lack of transparency from officials about the spread of the disease.
The recent upsurge in reported cases is also of wider concern because of the influx of visitors expected in July during the Muslim fasting month of Ramadan and during the annual Haj pilgrimage in October.
The World Health Organisation said outbreaks of MERS in the city's two main hospitals were partly due to breaches in its recommended infection prevention and control measures.