Scientists believe camels in Saudi Arabia are the main animal reservoir of MERS, a new disease that kills about a third of sufferers and has infected 339 people in the kingdom. (Stringer/Reuters)

Saudi Arabia has found 25 more cases of Middle East Respiratory Syndrome, or MERS, as the rate of infections rises and two more people have died from the new disease, according to the kingdom’s Health Ministry.

On Friday, seven people were confirmed as having MERS, followed by 18 more on Saturday, the biggest daily increase in new infections so far. The total number of cases in the kingdom is 396, of which 109 have proved fatal.

The new cases include nine in the capital, Riyadh; 10 in Jiddah; four in Mecca; and two in Medina. In July, many foreign pilgrims are expected to visit Mecca and Medina during Islam’s fasting month of Ramadan. Millions more are expected in early October for the annual Hajj, or pilgrimage to Mecca.

On Friday, the United States said it had discovered its first confirmed case of the disease in a man who had recently been in Saudi Arabia. Egypt said it discovered its first case, also in a man who had been in Saudi Arabia, on Thursday.

MERS infections in Saudi Arabia, where the disease was discovered two years ago, have more than doubled since the beginning of April, but the total number of deaths has increased at a slower rate.

A higher number of people without symptoms are also being found with the disease, suggesting that the rapid escalation in recent weeks is partly due to wider testing of people who have been in close contact with MERS patients.

MERS, a form of coronavirus like the more deadly SARS, can cause fever, coughing, shortness of breath and pneumonia. However, it is not easily transmitted between people and the World Health Organization has not advised any travel restrictions for Saudi Arabia.

Scientists say the most likely animal reservoir, from which new cases are becoming infected, is Saudi Arabia’s population of camels.