The novel H1N1 flu strain that originated in Mexico in the spring of 2009 has quickly spread across the globe, resulting in a pandemic declaration by the World Health Organization on June 11, 2009.
Most countries around the world have reported at least one case of the H1N1 virus, though most reported cases of illness have occurred in the US, Mexico, and Great Britain. According to the World Health Organization (WHO), there have been over 250,000 confirmed cases of H1N1 infection and almost 3,000 deaths. However, note that the number of confirmed cases is drastically under-representative of the virus' true impact, as most mild cases are not reported and most countries have stopped testing all suspected cases and are instead just tracking hospitalizations and deaths.
For the most up-to-date information regarding influenza cases across the United States, visit the CDC website here to view a map of regions most impacted by H1N1 infections, as well as the CDC's FluView weekly influenza surveillance report.
2009 H1N1 Attack Characteristics
A majority of those infected by the virus, as well as most of the severe cases and deaths have occurred in those under 50. This differs from the normal seasonal flu, which results in 90% of severe cases and death occurring in those 65 and older. At this stage, it appears all populations are susceptible to the disease, though older populations appear to have some immunity to the virus from previous exposure to other similar viruses, which likely correlates to the reversal in severe cases and death in those 65 and older.
While the Southern Hemisphere's influenza season is nearing its end, countries in the northern hemisphere are beginning to report both pocketed and widespread spikes in influenza-like illness (ILI). This may be in part to the resumption of school classes, where all levels of primary and secondary education are more likely to spread the virus, given social interaction in congregated areas.
Source: CDC H1N1 Investigation website www.cdc.gov/h1n1flu/investigation.htm and other public/media reporting
Projected Impact
Given the fact that H1N1 infections continued in most places during their summer months (when it is usually difficult for influenza viruses to spread), it is likely that the United States and other northern hemisphere countries will soon see dramatic spikes in the number of cases. While the virus remains relatively mild, it shows a strong ability to spread and overtake the other seasonal viruses in circulation.
The CDC is still advising that schools only consider closure when there is a magnitude of faculty or student absenteeism that interferes with the school's ability to function. Many employers across the US are preparing for a second wave, as even if widespread severe illness does not occur, there is a potential for the virus to result in absenteeism and lost productivity.
Government Response Actions/Recommendations
The US government is working with vaccine manufacturers to produce a vaccine as quickly as possible. It is likely, however, that vaccines will not be abundant enough to vaccinate all high-risk populations before the peak of the pandemic occurs in any specific area across the US.
The CDC has developed strategies to quickly distribute vaccines across the US to get the vaccine available to these high-risk populations as quickly as possible. High-risk populations include women who are pregnant, as well as anyone suffering from diabetes, heart disease, asthma, kidney disease, or neurological disorders.