Swine flu

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An outbreak caused by a novel strain of H1N1 influenza, commonly called "swine flu", began in Mexico in March 2009 and spread rapidly to many other countries. The virus contains a unique combination of swine, avian, and human influenza gene segments that had not been previously observed. Initial reports from Mexico indicated a high fatality rate in previously healthy young adults and older children, raising concerns that a worldwide pandemic might occur, similar to 1918. However, subsequent data from Mexico, as well as experience from other countries, indicated the H1N1 strain from 2009 is not nearly as lethal as some people initially feared. Preliminary data indicate that up to one-third of those greater than 60 years of age have antibodies against the novel H1N1 virus, whereas protective antibodies are found much less frequently in children and younger adults (see MMWR). This is consistent with the clinical experience, which indicates that the most severe cases have occurred in those younger than age 60.

On August 10, 2010, the World Health Organization declared the H1N1 influenza pandemic was over, saying worldwide flu activity had returned to typical seasonal patterns and many people had immunity to the virus.

To protect yourself from H1N1 influenza, wash your hands regularly and avoid close contact with anyone who is coughing or sneezing. Routine use of face masks is not recommended. The symptoms of H1N1 influenza include fever, cough, sore throat, body aches, headache, chills and fatigue, similar to seasonal influenza. Any traveler who develops flu-like symptoms after travel to a country which has reported H1N1 influenza should immediately seek medical attention. Empiric treatment with oseltamivir (Tamiflu) and zanamivir (Relenza) should be considered for suspected cases, though a small number of Tamiflu-resistant isolates have been described. The virus is resistant to amantadine and rimantadine. Vaccination against novel H1N1 influenza is recommended for everyone, except those allergic to the vaccine or one of its components. For further information on novel H1N1 influenza (swine flu), go to the World Health Organization and the Centers for Disease Control.

The following is the latest update from the World Health Organization:

Influenza H1N1 (2009) virus transmission remains locally intense in parts of India and New Zealand.

In India, the number of new H1N1 (2009) cases per week, including fatal cases, continued to increase since mid June 2010 in several states, particularly in the western state of Maharashtra and to a lesser extent in Gujarat, Andhra Pradesh, and West Bengal. The current epidemic of influenza H1N1 (2009) does not appear to have peaked yet in these states. Overall, 79 new laboratory confirmed H1N1 (2009) associated deaths were officially reported across India during the week of August 2-8. During last two weeks of July 2010, more than 1/3 of respiratory specimens tested positive for influenza virus in the state of Maharashtra, all of which were H1N1 (2009). In the southern Indian state of Kerala, where recent influenza activity in India was first detected, transmission of H1N1 (2009) virus appears to have peaked during late June and early July 2010 and has declined substantially since. Seasonal influenza B viruses are also known to be currently circulating in India, although at lower levels than H1N1 (2009) viruses.

In New Zealand, the national consultation rate for ILI continued to increase, particularly in recent weeks, passing the seasonal baseline during the last week of July 2010. The majority of influenza viruses detected during the current winter epidemic have been H1N1 (2009). Influenza activity (as indicated by rates of ILI, hospitalizations, and absenteeism) has been geographically uneven but focally intense in some areas, particularly those areas that experienced milder epidemics during the previous winter 2009 pandemic wave. Nationally, overall rates of ILI and numbers of severe and fatal cases remain well below levels seen during the winter 2009 pandemic wave, however, the situation continues to evolve and the current epidemic has yet to peak.

Except in South Africa and New Zealand, overall influenza activity and rates of respiratory diseases remained low in other countries of the temperate southern hemisphere (Australia, Chile, and Argentina). In South Africa, active circulation of seasonal influenza H3N2 and type B viruses was observed during June and July 2010.

Influenza H1N1 (2009) continued to circulate at low to moderate levels over the past month in the tropics of the Americas (Costa Rica, Colombia, Peru, Bolivia, Brazil), West Africa (Ghana), and South and Southeast Asia (India, Bangladesh, Thailand, Cambodia, Singapore, Malaysia).

Variable circulation of seasonal influenza viruses continues to be detected in all regions of the world. Seasonal influenza H3N2 viruses have recently circulated in the tropics of the Americas (particularly in several Central American countries), in southern and western Africa, and in parts of Southeast Asia. The most active areas of influenza type B virus circulation continue to be in parts of central and southern Africa.

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