• The pandemic virus to spread rapidly due to the high level of global traffic;
• Vaccines, antiviral agents and antibiotics to treat secondary infections to be in short supply, with a period of several months before any vaccine becomes available;
• Medical facilities to be overwhelmed with demands to care for both influenza and non-influenza patients;
• Widespread illness to result in sudden and potentially significant shortages of personnel to provide essential community services.

Each year the World Health Organization makes predictions about which new strains will be the most virulent, and health officials redesign vaccines accordingly

In addition, there are 110 WHO National Influenza Centers in 83 countries and four WHO Collaborating Centres for Virus Reference and Research in Australia (Melbourne), Japan (Tokyo), the United Kingdom (London) and the USA (Atlanta),  tracking influenza infection levels

The World Health Organization (WHO) categorizes risk of Pandemic  into a multi-phase timeframe:

Phase 1 – Naturual circulation influenza viruses among animals, especially birds. No virus transmission to Humans detected. Risk of Pandemic low.

Phase 2 – Detection of transmission of Influenza virus from animal to Human. Risk of Pandemic Low to Moderate.

Phase 3 – A novel strain, animal or human-animal influenza reassortant virus has caused sporadic or small cluster of cases,  with no human-to-human transmission sufficient to sustain community-level outbreaks. Limited human-to-human transmission may occur under close contact. Risk of Pandemic Moderate.

Phase 4 - Human-to-human transmission of influenza  virus able to cause outbreaks in the community. Risk of Pandemic Moderate to High

Phase 5 - Human-to-human spread of the virus into at least two countries in one WHO region. Risk of Pandemic High

Phase 6 – The Pandemic phase, is marked by multiple outbreaks within community in at least one other country in a different WHO region in addition to the criteria defined in Phase 5.

Post-peak period – Influenza case levels in most countries have dropped below the peak observed levels. This period suggests that pandemic activity appears to be decreasing; however, previously recorded pandemics tend to have shown that  additional waves might occur, by waves of activity spread out over months

Post-pandemic period - Influenza  activity will have returned to levels normally seen, with  seasonal trends. At this stage, it is important to maintain surveillance and update pandemic preparedness and response plans accordingly. An intensive phase of recovery and evaluation may be required.