2010 Updates :
August 10, 2010 -- The World Health Organization declared H1N1 has run its course and they declared we are in the post-pandemic phase. Localized outbreaks as currently happening in New Zealand are expected and these situations will be monitored.
April 2010, H1N1 activity has slowed, with the exception of a increase in cases seen in the southeast US with more hospitalizations reported now than last fall when H1N1 was widespread in the US. Officials are monitoring the situation and waiting to see if this is the beginning of a third wave of the pandemic virus. The World Health Organization (WHO) is monitoring the situation in the southern hemisphere before declaring we are in the post peak pandemic phase.
In the United States, winter is the traditional time for seasonal influenza. Flu outbreaks can happen as early as October, however most of the time influenza activity peaks in January or later. In 2009, the flu season did not end, but continued with the outbreak and worldwide spread of 2009 H1N1. This new virus was first detected in Mexico and then in the United States, April 2009. June 2009, the World Health Organization (WHO) declared 2009 H1N1 a pandemic and warned to expect a second wave of the virus, fall 2009.
Seasonal influenza is a respiratory illness that can be transmitted from person to person. Most people have some immunity to seasonal flu and typically seasonal flu vaccine is available for populations at risk and the general public. Each year in the United States, more than 200,000 people are hospitalized due to seasonal flu an estimated 36,000 people die from flu-related complications.
Pandemic influenza is a global outbreak of disease that occurs when a new influenza A virus appears in the human population, causing serious human illness and spreading easily from person-to-person worldwide. Because people have little or no immunity protection from such a new virus, there can be high levels of illness, death, social disruption, and economic loss. There have been on average, three pandemics every 100 years and they can occur years apart or back-to back. The last major influenza pandemic occurred in 1918 (known as the Spanish Flu) and killed as many as 50 million people worldwide, including more than 500,000 in the United States. This is not the only pandemic influenza to occurr in the US in the past 100 years. For details of the 1957-1958 and 1968-1969 pandemics see the Center for Infectious Diseases, Research & Policy (CIDRAP).
2009 H1N1 (referred to as “swine flu” early on) is a new influenza virus causing illness in people worldwide. This new virus was first diagnosed in people in the United States, April 2009. On June 11, 2009, the World Health Organization signaled that a pandemic of 2009 H1N1 flu was occurring and elevated the Pandemic Alert to Phase 6. This designation was a signal to the world to plan and prepare.
August 2009, the 2009 H1N1 influenza virus is the predominate influenza virus in circulation worldwide. The epidemiology (study of factors affecting the health and illness of populations) of the disease caused by the 2009 H1N1 influenza virus currently circulating in the Southern Hemisphere is very similar to that seen in the United States earlier this year. According to CDC and WHO, the current virus circulating looks similar to A/California/07/2009 (the reference virus selected by WHO as a potential candidate for the new 2009 H1N1 vaccine).
August 30, 2009 marked the beginning of the 2009-2010 influenza season as as of that date CDC began providing aggregate reports of all influenza and pneumonia-associated hospitalizations and deaths, including 2009 H1N1 and seasonal flu. The official influenza season began October 4, 2009.
December 10, 2009 the CDC released revised estimates of 2009 H1N1 influenza cases, hospitalizations and deaths in the US April through November 14 of this year. The revised estimates indicate about 47 million people have had 2009 H1N1, there have been 213,000 hospitalizations and almost 10,000 deaths, about 1,000 in youth under the age of 18. For more information on how these estimates were derived see -- CDC flu estimates.
2009 H1N1 vaccine shipment and distribution has begun in the United States, with first doses of vaccine being given to first responders, with priority high risk groups to follow. As vaccine supply has increased, vaccine distribution has expanded to all children over 6 months of age and under 24 years old. It remains only those over 24 and under 64 with chronic health conditions should receive the vaccine. To track supply and distribution for your state, check, CDC 2009 H1N1 Vaccine Supply page.
As H1N1 has spread, in recent weeks there has been concern about the growing number of cases and deaths in the Ukraine, which has led to speculation the virus may have mutated. WHO released a good news statement that in fact preliminary tests indicate there have been no significant changes in the virus. Mutations to the virus have been detected in other countries including most recently Norway. WHO reports scientists are tracking the changes and thus far there is no indication the virus has become more virulent.
There has also been recent reports on identification of H1N1 anti-viral resistant clusters in the UK and US. CIDRAP reports in both instances the patients were severely ill added to the mutation ability of influenza viruses, this finding did not surprise the medical professionals, but surveillance continues on this front.