Eighteen more people in Saudi Arabia have contracted the potentially deadly Middle East Respiratory Syndrome (Mers), bringing the number of cases in the kingdom to 414, its health ministry said, more than a quarter of whom have died.

The new cases were in the capital Riyadh, the coastal city of Jeddah, and the holy cities of Mecca and Medina, the ministry said on its website.

The spread of the disease is a concern for Saudi Arabia which will host millions of foreign pilgrims in July in Mecca and Medina during Islam’s fasting month of Ramadan. Millions more are expected in October for the annual Haj pilgrimage.

So far 115 of the people in Saudi Arabia who contracted the virus have died, the ministry said. Many of those affected have been foreign health workers.

Meanwhile, the first US patient to test positive for the virus is off supplemental oxygen and walking around his hospital room in Munster, Indiana, as health officials plan the man’s release, state and federal authorities said. The patient is a healthcare worker employed in Saudi Arabia.

Mers is a form of coronavirus like the more deadly Sars. It can cause fever, coughing, shortness of breath and pneumonia but it is not easy to transmit between people. The WHO has not advised any travel restrictions for Saudi Arabia.