Tourists wearing masks fill in health declaration cards after their arrival at Ngurah Rai airport, in Indonesia's resort island of Bali June 12, 2009. Indonesia's government is distributing health declaration cards to all tourists as part of preventive measures against the spread of Influenza A (H1N1) in the country.

GENEVA, June 22 (Xinhua) -- The world's total number of laboratory confirmed A/H1N1 influenza cases has increased to 52,160, with 231 deaths, the World Health Organization (WHO) said in a latest update on Monday.

Of that total, 7,873 cases, including 51 deaths, were reported in the past three days, the UN agency said.

The United States has reported a total of 21,449 cases, the largest number among all countries and regions. It is followed by Mexico (7,624), Canada (5,710), Chile (4,315), Britain (2,506), Australia (2,436), Argentina (1,010) and others. So far most of the deaths occurred in Mexico (113) and the United States (87). But some other countries have also reported deaths, including Canada (13), Argentina (7), Chile (4) and Colombia (2).

Earlier this month, the WHO raised its pandemic alert to the highest level of six, formally declaring the first pandemic in the 21st century.