There is considerable talk of pandemic phases in the media. This article hopes to shed light on pandemic phases and their significance.
The World Health Organization (WHO) first described pandemic phases in a guidance document released in 2005. The document was informed by the spread of Avian (H5N1) influenza in 2003. That document described six pandemic phases at the time.
In 2009, the WHO updated its guidance, retaining the six-phase structure but regrouping and redefining the phases to more accurately reflect pandemic risk and the epidemiological situation based upon observable phenomena.
The revised guidance harmonizes the recommended measures with International Health Regulations 2005 (IHR 2005) and the concurrent development/revision of WHO guidance in related areas such as pandemic influenza surveillance, disease control measures, rapid containment and communications. It also includes suggested planning assumptions, their implications and a selected evidence base to aid planning efforts on a national level.
The phases are applicable globally and provide a framework to aid countries in pandemic preparedness and response planning.
While the phases were described keeping potential influenza outbreaks in mind, they can be applied to any communicable disease. Nevertheless, much of the terminology employed is in relation to influenza simply because that is what the guidance was developed for in the first place. For this article, I will omit mention of influenza, so that one can instantly apply the phases to any communicable disease. Similarly, while the original guidance document mentions only influenza virus (but other disease agents like bacteria may also cause outbreaks), I will use more generic terms here.