Influenza A(H1N1) pandemic: 2 years after.

Dear Sir, In 2009, the emergence of the new H1N1 influenza virus saw the world brace itself for the first influenza pandemic since 1968. Two years after, it is time to evaluate the situation of that Influenza A(H1N1) pandemic and its combat measures. First, alert level was raised rapidly from level 3 to level 6 in 6 weeks. On 25 April 2009, the WHO declared a level 3 Influenza Pandemic Alert. Three days after, level 4 alert was declared due to international spread of clusters of human-to-human transmission. The continuous confirmation of new cases in various countries required the WHO to raise the pandemic alert to level 5, less than 1 week after declaring level 3. The maximum alert response was declared on the 11 th of June, meanwhile most human infections appeared to be mild [1]. Recent study analysed the records of past influenza outbreaks to determine a definition for pandemics. The authors concluded that defining an influenza pandemic on the early observations may be adequate to declare an alerting response but doesn't assure worldwide spread or excess mortality [2]. Second, the WHO reported an estimate of 22-33% of secondary attack rate among contacts of H1N1 influenza , however chemoprophylaxis was given to contacts without previous studies regarding its effectiveness in outbreaks or epidemics. Contacts received antivirals for 10 days, meanwhile patients with mild and moderate symptoms of influenza received antivirals for only 5 days [3]. A study published in 2009 proved that secondary attack rate among house hold contacts of cases of H1N1 was only 7.6%, which was much lower than the reported figures by the WHO. This study also proved that rates of infection did not differ significantly in those receiving chemoprophylaxis compared to household contacts that didn't receive chemoprophylaxis [4]. Third, use of masks by the general population and in airports proved to be inefficient and unnecessary. It rather gave a sensation of panic and insecurity. A study was done in France to evaluate the use of protective measures in prevention of acute respiratory symptoms for French participating in Hajj of 2009. This study showed that although 79% of the subjects used facemask this didn't significantly reduced the acute respiratory symptoms among them [5]. A recent systemic review evaluated the effectiveness of facemasks in prevention of H1N1 infection and concluded that wearing face masks for infected people could protect others but there are fewer data to …