The recent arrival of cases of MERS or Middle East respiratory syndrome in North America has focused attention on the viral infection.

On Tuesday, the World Health Organization said MERS is not an international public health emergency, but added there is a clear sense of urgency around the illness.

The outbreak itself is accelerating in the Arabian Peninsula, particularly in Saudia Arabia. There are nearly 600 confirmed cases.

"What they reached was a consensus that the situation had increased in seriousness and their concern about the situation had also increased in terms of urgency. However, when they looked at all of the information, they felt that the situation still fell short of calling it a public health emergency of international concern," said Dr. Keiji Fukuda, an assistant director general of WHO.

What is it?

MERS is caused by the Middle East respiratory syndrome coronavirus. A coronavirus cousin caused the 2003 SARS outbreak.

What are the symptoms?

Most people infected with the MERS virus develop severe acute respiratory illness with symptoms of fever, cough and shortness of breath. So far, about  25 to 30 per cent of them have died, according to the U.S. Centers for Disease Control and Prevention.

Some patients have described it as a mild respiratory illness.

When did it emerge?

It was first reported in September 2012 in Saudi Arabia.

How is it transmitted?

This hasn’t been completely nailed down. The virus spreads between people who are in close contact, such as family members exposed to the bodily fluids of a sick loved one. It has also been transmitted to health-care workers.

There haven’t been any documented cases of the virus being contagious without close contact, such as sitting next to someone on an airplane.

What is the source of the virus?

The MERS coronavirus has been found in camels. How humans catch the virus from camels is unclear, and not all patients have reported contact with the animals. Health authorities urge people to avoid unpasteurized camel milk and cheeses and to eat camel meat only when it is well-cooked. The virus has also been found in a bat in Saudi Arabia.

What does the outbreak mean for travellers?

Dr. Gregory Taylor, Canada’s deputy chief public health officer, said standard advice to travellers applies, such as:

  • Check your vaccinations are up to date.
  • Avoid people who are clearly ill.
  • Wash your hands frequently.
  • Practise the "Canadian salute" of coughing and sneezing into your elbow.
  • Stay home when sick.
  • Check for any symptoms, typically for seven days, after travel to the Arabian Peninsula.

The acceleration in cases is a public health concern given that the Islamic month of Ramadan, which starts at the end of June this year, is historically a time when three to four million pilgrims travel to Saudi Arabia, said Dr. Kamran Khan, an infectious disease physician at Toronto’s St. Michael Hospital.

Khan suggested that travellers to Saudi Arabia talk to their health-care provider about the risks, be aware of exposure to camels, camel milk or meat and visits to health-care institutions and watch for any symptoms for two weeks after returning. If any symptoms do appear, it’s important to tell your health-care provider about your recent travel history and that of family members.

What is the treatment?

There are currently no vaccines or specific treatments.

With files from CBC's Amina Zafar, U.S. Centers for Disease Control and Prevention, Canadian Press