A Pandemic Is Declared
On June 11, 2009, the World Health Organization (WHO) raised the worldwide pandemic alert level to Phase 6 in response to the ongoing global spread of the novel influenza A (H1N1) virus. A Phase 6 designation indicates that a global pandemic is underway.
More than 70 countries are now reporting cases of human infection with novel H1N1 flu. This number has been increasing over the past few weeks, but many of the cases reportedly had links to travel or were localized outbreaks without community spread. The WHO designation of a pandemic alert Phase 6 reflects the fact that there are now ongoing community level outbreaks in multiple parts of world.
WHO’s decision to raise the pandemic alert level to Phase 6 is a reflection of the spread of the virus, not the severity of illness caused by the virus.
A New Influenza Virus
Novel influenza A (H1N1) is a new flu virus of swine origin that was first detected in April, 2009. The virus is infecting people and is spreading from person-to-person, sparking a growing outbreak of illness in the United States. An increasing number of cases are being reported internationally as well.
It’s thought that novel influenza A (H1N1) flu spreads in the same way that regular seasonal influenza viruses spread; mainly through the coughs and sneezes of people who are sick with the virus.
It’s uncertain at this time how severe this novel H1N1 outbreak will be in terms of illness and death compared with other influenza viruses. Because this is a new virus, most people will not have immunity to it, and illness may be more severe and widespread as a result. In addition, currently there is no vaccine to protect against this novel H1N1 virus. CDC anticipates that there will be more cases, more hospitalizations and more deaths associated with this new virus in the coming days and weeks.
Novel influenza A (H1N1) activity is now being detected through CDC’s routine influenza surveillance systems and reported weekly in FluView. CDC tracks U.S. influenza activity through multiple systems across five categories. The fact that novel H1N1 activity is now detected through seasonal surveillance systems is an indication that there are higher levels of influenza-like illness in the United States than is normal for this time of year. About half of all influenza viruses being detected are novel H1N1 viruses.
 Content provided and maintained by the US Centers for Disease Control and Prevention (CDC).
Last Updated: 9/4/09
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