Hong Kong and Denmark have joined the list of countries that have confirmed cases of the H1N1 flu virus.
In Mexico, where it started, people have been told to stay at home for five days to try to slow the rate of infection.
Dr Hussam al-Soub, a consultant for infectious diseases at the Hamad hospital in the Qatari capital Doha, answered a series of questions on the virus from Al Jazeera viewers.
