BEIJING, June 12 (Xinhua) -- The World Health Organization (WHO) on Thursday raised the level of influenza pandemic alert to the highest phase 6. The following is a pandemic phase description by the WHO.
In Phase 1, no animal influenza virus circulating among animals have been reported to cause infection in humans.
In Phase 2, an animal influenza virus circulating in domesticated or wild animals is known to have caused infection in humans and is therefore considered a specific potential pandemic threat.
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.
Phase 4 is characterized by verified human-to-human transmission of an animal or human-animal influenza reassortant virus able to sustain community-level outbreaks.
In Phase 5, the same identified virus has caused sustained community level outbreaks in two or more countries in one WHO region. The declaration of Phase 5 is a strong signal that a pandemic is imminent and that the time to finalize the organization, communication, and implementation of the planned mitigation measures is short.
Phase 6, the pandemic phase, is characterized by community level outbreaks in at least one other country in another WHO region in addition to the criteria defined in Phase 5. Designation of this phase will indicate that a global pandemic is under way.
The severity of pandemics can change over time and differ by location or population.
During the post-peak period, pandemic diseases levels in most countries with adequate surveillance will have dropped below peak observed levels. The post-peak period signifies that pandemic activity appears to be decreasing; however, it is uncertain if additional waves will occur and countries will need to be prepared for a second wave.
The definition by the WHO has to do with the geographic spread of the disease, thus the declaration of a pandemic doesn't mean anything concerning severity.
The WHO recommends that countries, institutions, media and the public have a proper understanding of the pandemic to prevent an excessive panic that may lead to bad consequences and overreactions.
Special Report: World Tackles A/H1N1 Flu
