Pandemic Influenza

Introduction

Emergence of Influenza A(H1N1)

A teacher demonstrates to children how to wash their hands, as a precautionary measure against influenza infection, at a kindergarten in Huaibei, Anhui province, China.

UNICEF is working with WHO and partners, coordinated by the UN System Influenza Coordinator (UNSIC), to prepare countries for an appropriate response to the emergence of the 2009 Influenza Virus (H1N1) as a pandemic threat.

On 11 June 2009, WHO declared phase 6: the start of a pandemic. On 24 April used the International Health Regulations 2005 to declare a “Public Health Emergency of International Concern”, and changed the pandemic alert status to phase 4 on 27 April and to phase 5 on 29 April based on evidence of sustained virus spread in the United States as well as in Mexico. Despite spread of the virus, with 74 countries reporting nearly 30,000 confirmed cases by 11 June, response measures appear to have controlled further spread.

Avian influenza H5N1
The threat of H5N1 virus remains. UNICEF also has pandemic-relevant material, including descriptions of various communication campaigns, in its site on avian influenza, as the concern about the H5N1 avian influenza virus adapting to humans and causing a pandemic remains.

After a pandemic virus emerges and spreads around the globe, it stays and usually replaces the Influenza A virus that had been causing seasonal flu. Thus, the pandemic virus becomes seasonal influenza as the world's population acquires immunity over the pandemic strain. It causes a pandemic because there is little or no immunity in the human population to the new virus. However, after several waves of spread, there is sufficient immunity to the new pandemic virus that in subsequent years it causes seasonal influenza that usually replaces the previous strain causing seasonal influenza.