Beginning in March 2009, an outbreak of influenza in North America was found to be caused by
a new strain of influenza virus, designated Influenza H1N1 2009, which is a reassortant of
swine, avian and human influenza viruses. Over a thousand total cases were identified with the
first month, chiefly in the United States and Mexico, but also involving several European countries.
On April 15 and April 17, 2009, novel swine-origin influenza A (H1N1) virus (S-OIV) was
identified in specimens obtained from two epidemiologically unlinked patients in the United
States. The same strain of the virus was identified in Mexico, Canada, and elsewhere. On June
11, 2009, the World Health Organization raised its pandemic alert level to the highest level,
phase 6, indicating widespread community transmission on at least two continents. In India the
first case was detected in May 2009 in Hyderabad and by mid August there have been more
than one thousand five hundred cases tested positive and more than 45 patients have died. 0ur
previous article on Swine Flu in April issue of this journal briefly discussed this disease. In this
article we will review this disease with updated information on the epidemiology, clinical
manifestations, diagnosis, treatment and preventive strategies for pandemic H1N1 influenza A
virus infection.