World Health Organization announces flu pandemic alert change

GENEVA The current situation regarding the outbreak of swine influenza A(H1N1) is evolving rapidly, the World Health Organization stated in a press release Monday.

“As of 27 April, the United States government has reported 40 laboratory confirmed human cases of swine influenza A(H1N1), with no deaths. Mexico has reported 26 confirmed human cases of infection with the same virus, including seven deaths. Canada has reported six cases, with no deaths, while Spain has reported one case, with no deaths,” WHO stated.

In responose, WHO Director-General Margaret Chan has raised the level of influenza pandemic alert from the current phase 3 to phase 4. 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.

In Phase 3, an animal or human-animal influenza reassortant virus has caused sporadic cases or small clusters of disease in people, but has not resulted in human-to-human transmission sufficient to sustain community-level outbreaks. Limited human-to-human transmission may occur under some circumstances, for example, when there is close contact between an infected person and an unprotected caregiver. However, limited transmission under such restricted circumstances does not indicate that the virus has gained the level of transmissibility among humans necessary to cause a pandemic.

Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to cause “community-level outbreaks.” The ability to cause sustained disease outbreaks in a community marks a significant upwards shift in the risk for a pandemic. Phase 4 indicates a significant increase in risk of a pandemic but does not necessarily mean that a pandemic is a forgone conclusion.

Phase 5 indicates an imminent pandemic and phase 6 signifies an actual pandemic.