In a statement released by the WHO Director-General, Dr. Margaret Chan, alert has been raised on the level of the influenza pandemic from the current phase 3 to phase 4. The Emergency Committee of the World Health Organisation (WHO), established in compliance with the International Health Regulations (2005), held its second meeting on 27 April 2009.  The Committee considered available data on confirmed outbreaks of A/H1N1 swine influenza in the United States of America, Mexico, and Canada. The Committee also considered reports of possible spread to additional countries.

The change to a higher phase of pandemic alert indicates that the likelihood of a pandemic has increased, but not that a pandemic is inevitable. As further information becomes available, WHO may decide to either revert to phase 3 or raise the level of alert to another phase.

This decision was based primarily on epidemiological data demonstrating human-to-human transmission and the ability of the virus to cause community-level outbreaks. Given the widespread presence of the virus, the Director-General considered that containment of the outbreak is not feasible. The current focus should be on mitigation measures.

The Director-General recommended not to close borders and not to restrict international travel. It was considered prudent for people who are ill to delay international travel and for people developing symptoms following international travel to seek medical attention.

The Director-General considered that production of seasonal influenza vaccine should continue at this time, subject to re-evaluation as the situation evolves. WHO will facilitate the process needed to develop a vaccine effective against A/H1N1 virus.

The Director-General stressed that all measures should conform with the purpose and scope of the International Health Regulations.