» The World Health Organization raised its global pandemic alert level for the swine flu from three to four on April 27.

» Level 4 means that there has been sustained human-to-human transmission.

» The number of deaths caused by the flu in Mexico has climbed to 149 as of April 27, with a total of 1,995 suspected case.

» The United States reported 40 infections so far.

» A number of countries also reported suspicious cases.

» China has not report any cases yet. Regulators said measures have been taken to prevent the virus from entering the country.