Saudi Arabia has announced that 10 people infected with Middle East Respiratory Syndrome (MERS) died during the last two days and that 20 new cases of the virus were identified, pushing the total number of infections in the country to 529 and deaths to 168.
Five of the deaths were reported on Tuesday and five on Wednesday, according to statements on the health ministry's website.
MERS, a coronavirus like Severe Acute Respiratory Syndrome (SARS), was identified two years ago.
The World Health Organisation said on Wednesday that while concern about the virus had "significantly increased", the disease was not yet a global health emergency.
The speed of infection in Saudi Arabia has surged in recent weeks after big outbreaks associated with hospitals in Jeddah and Riyadh. The total number of infections nearly doubled in April and has risen by a further 25 percent already in May.
The recent upsurge is of particular concern because of the influx of pilgrims from around the world expected in July during the holy month of fasting, Ramadan.
Saudi's Hajj Ministry makes no special mention of MERS ahead of the 2014 pilgrimage, which is expected to fall in October.
Scientists around the world have been searching for the animal source, or reservoir, of MERS virus infections ever since the first human cases were confirmed in September 2012.
SARS killed about 800 people worldwide after emerging in China in 2002.