Travellers are understandably worried. A new virulent form of pneumonia has now killed over 50 people in 13 states - including the Italian doctor who first identified the disease. Severe acute respiratory syndrome (Sars) began in the south Chinese province of Guandong late last year, but thanks to global travel has spread rapidly. Some 685 people are infected in Hong Kong, more than 80 living in a single residential block becoming infected over a four-day period. Britain has three cases, Canada 37 and the US 60. The world's most senior medical specialists remain uncertain of its cause or treatment. The director of the US centres for disease control (CDC) in Atlanta, warned this week that "we may be in the early stages of what could be a much larger problem."

Inevitably scaremongers have pointed to earlier global epidemics, most notoriously the 1918-19 influenza pandemic that killed 20 million. But that was in an age which did not have the antibiotics and antiviral drugs of today. Before the 1940s, pneumonia killed about a third of its victims, but today with proper medical treatment, more than 95% recover. The most reassuring aspects of the new disease is that it has a low death rate (below 4%), a high rate of recovery, and a comparatively restricted infection rate. It looks as though infection spreads through close face-to-face contact, which occurs between family members or a doctor and patient, but scientists have still not ruled out airborne transmission, which would be much more serious.

Sensibly, no travel restrictions have been put in place. It is much too early for that, but it will be a good test for the World Health Organisation's new global alert network set up to fight epidemics.