CARACAS -- A total of 724 people have been infected with the A/H1N1 bird flu virus so far this year in Venezuela, the Health Ministry said Thursday.

Cases were reported in almost all states, with Caracas and the states of Merida, Tachira, Zulia and Lara being the most affected regions, the ministry said.

There was an upsurge of infections in May as cases rose from 236 at the beginning of the month to 724 at the end.

National and local health authorities have strengthened sanitary measures, especially at hospitals, to contain the spread of the virus.

Residents in the most affected regions were told to wear masks and wash hands frequently, and to see doctors once symptoms appear.

Some 1,000 A/H1N1 cases were reported in Venezuela in 2011.