The accusations that are being leveled against the World Health Organisation contending that the health watchdog acted 'too slowly' in the face of the pandemic, has prompted the UN agency into examining its own response to the swine flu outbreak in Mexico.
Spokesman Thomas Abrahams said WHO headquarters was informed by the US Centers for Disease Control (CDC) about the emergence of a new flu virus early on April 24.
"There are case of influenza all the time, but once we knew that this illness was cause by a new influenza virus... we moved into operation within a matter of hours," he told journalists.
"One of the things we are doing internally is documenting everything we have done, when we did it and how we have done it," Abrahams added.
Media reports in recent days said there was a delay of eight days in the WHO's response to swine flu which has now been termed A(H1NI) flu by the WHO.
Mexican health authorities notified the WHO's Washington-based regional branch, the Pan American Health Organisation (PAHO), on April 16 of a possibly brewing epidemic, following "unusual pneumonia cases", according to the Washington Post's website.
A US bio-surveillance firm, Veratect, said on its website that its tracking reports of atypical pneumonia and respiratory disease in Mexico early last month were made available to the WHO.
Bolstered international health regulations introduced in 2005 were meant to beef up the speed of the WHO's response to emerging and suspicious cases of illness in a country.
Its regional offices, such as PAHO, form local hubs of communication between countries and Geneva headquarters under the system.
Abrahams said: "On Friday 24, I think we were informed early in the morning. Immediately after that our strategic operations centre went into action."
WHO chief Margaret Chan, who was on an official trip to Washington, met US and Mexican officials and went to PAHO, then flew back to Geneva the next day.
"By Saturday evening she was making a public statement here saying we had a potential pandemic virus. I think this is a pretty rapid response," he added.