Global Alert and Response (GAR)

Pandemic (H1N1) 2009 - update 109

Weekly update

As of 12 July, worldwide more than 214 countries and overseas territories or communities have reported laboratory confirmed cases of pandemic influenza H1N1 2009, including over 18337deaths.

WHO is actively monitoring the progress of the pandemic through frequent consultations with the WHO Regional Offices and Member States and through monitoring of multiple sources of information.

Situation update:

Worldwide, overall pandemic influenza activity remains low. The most active areas of pandemic influenza virus transmission currently are in parts of South Asia, West Africa, and Central America. In the temperate zone of the southern hemisphere, pandemic and seasonal influenza activity has remained low during the first half of the southern hemisphere winter, except in South Africa, where increased detections of primarily seasonal influenza viruses (type B and H3N2) were reported during late June and early July 2010. Seasonal influenza H3N2 viruses continue to circulate at varying levels across parts of the Americas, Africa, and Southeast Asia. Increased seasonal influenza activity continues to be observed in several countries of Central America.

To date, most countries of the temperate zone of the southern hemisphere, with the exception of South Africa, have reported low overall levels of respiratory disease activity and low to sporadic levels of pandemic and seasonal influenza virus circulation during the first half of the southern hemisphere winter season. Pandemic influenza viruses have been detected only sporadically or at low levels in most of these countries. As reported last week, South Africa began observing a sharp increase in the proportion of sentinel respiratory samples testing positive for influenza virus (primarily seasonal influenza B and H3N2) during late June 2010, reaching a peak of ~50% detection rate during the first week of July 2010, and falling to ~40% during the second week of July 2010. In Chile (as of late June 2010) and Argentina (as of early July 2010), the most recent available data show that influenza activity remains sporadic in Argentina and low in Chile (~5% respiratory samples tested positive for influenza, 84% of which were pandemic virus with small numbers of seasonal influenza H3N2 and type B detected as well). In both Chile and Argentina, RSV has been the predominant circulating respiratory virus since mid-April 2010. In Australia, as of the last week of June 2010, overall rates of ILI remained low and below levels observed during the same period in past three winter seasons. Although a small cluster of pandemic influenza cases, including a few hospitalized cases, were recently detected in the Northern Territory of Australia, pandemic and seasonal influenza virus detections remain otherwise sporadic, albeit slightly increased during late June and early July 2010. Similarly, in New Zealand, rates of ILI have remained low and below the seasonal baseline, with only sporadic detections of pandemic and seasonal H3N2 viruses through the first week of July 2010. In both Australia and New Zealand, current levels of ILI are similar to those observed during the same period in 2008, when the influenza season was noted to have arrived and peaked late in winter.

In Asia, overall pandemic influenza activity remains low to sporadic, except in parts of southern and western India, Malaysia, and Singapore. As reported last week, in India, transmission of pandemic influenza virus remains active but stable in the southern state of Kerala. The extent of illness in the community is currently being assessed and monitored by the Government of India. Similar numbers of new cases, including small numbers of fatal cases, have been reported on a weekly basis since transmission first increased during mid-June 2010. Recent, small increases in pandemic influenza virus circulation have also been observed since mid-June 2010 in other southern and western states of India, particularly in the western state of Maharashtra. In Singapore, levels of ARI increased during the first two weeks of July 2010; however, the intensity of pandemic influenza virus transmission has declined during June and July 2010 after peaking in May 2010. The proportion of patients with ILI testing positive for pandemic influenza virus in Singapore remained stable (14-16%) during first two weeks of July 2010. In addition, substantial co-circulation of seasonal influenza H3N2 viruses (with pandemic H1N1 virus) was detected in Singapore throughout May and June 2010. In Malaysia, numbers of new cases of pandemic influenza continued to decline; overall pandemic influenza activity fell substantially in June and early July 2010 after peaking during mid-April to mid-May 2010. Low levels of seasonal influenza type B viruses (and to much lesser extent pandemic influenza virus) continue to circulate across northern and southern China as levels of ILI remain stable and near seasonal levels seen in the same period in recent years. Low levels of pandemic and seasonal influenza (H3N2 and type B) viruses also continued to circulate in Hong Kong SAR (China), Chinese Taipei, and parts of Thailand.

In the tropical regions of the Americas, overall pandemic and seasonal influenza activity remained low, except in parts of Central and South America, where there has been recent active co-circulation of pandemic and seasonal influenza H3N2 viruses. The majority of recent active transmission of pandemic influenza virus has been reported in Colombia, Costa Rica, and to a lesser extent in Cuba. In Colombia, although low level circulation of pandemic influenza viruses has persisted throughout the first half 2010, a second period of active transmission began in mid-May 2010, peaked in June 2010, has now largely subsided during the second of week of July 2010. Similarly, in Costa Rica, low level circulation of pandemic virus has persisted throughout 2010, however, there has been a recent resurgence in active transmission (though less intense than the initial 2009 wave) of pandemic influenza virus during June 2010. As reported previously, in Panama, a sharp increase in the circulation influenza A viruses (particularly H3N2, but also small numbers of pandemic H1N1) was reported over the month of June 2010; a high intensity of respiratory diseases and a moderate impact on healthcare services continued to be reported during the second week of July 2010. In Nicaragua, recent active transmission of seasonal influenza H3N2 viruses, which began during late May 2010 and peaked during mid June 2010, appears to have largely subsided during recent weeks. Many countries in the region continue to report ongoing co-circulation of other respiratory viruses, most notably RSV.

In sub-Saharan Africa, the current situation is largely unchanged since the last update. Pandemic and seasonal influenza activity continues to be observed in several countries. Ghana, in West Africa, continued to have a sustained resurgence in circulation of pandemic influenza virus during June 2010, more than several months after the first period of pandemic activity peaked (early April 2010). Seasonal influenza type B viruses continue to circulate in parts of central and southern Africa, particularly in Cameroon, where an increase in influenza type B virus circulation was observed during June 2010. Small numbers of seasonal H3N2 viruses continue to be detected across Africa, particularly in eastern and southern Africa; the most recent detections have been reported in Kenya and South Africa.

Overall, in the temperate regions of the northern hemisphere (North America and Europe), pandemic and seasonal influenza viruses have been detected only sporadically or at very low levels during the past month.

*Countries in temperate regions are defined as those north of the Tropic of Cancer or south of the Tropic of Capricorn, while countries in tropical regions are defined as those between these two latitudes.

**Abbreviations: influenza-like-illness (ILI), acute respiratory infection (ARI), and severe acute respiratory infection (SARI)

MAP OF INFLUENZA ACTIVITY AND VIRUS SUBTYPES (WEEK 26: 20 JUNE - 3 JULY 2010)

  • Map of influenza activity and virus subtypes
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    Description: Displayed data reflect the most recent data reported to Flunet (www.who.int/FluNet), WHO regional offices or on Ministry of health websites in the last 2 weeks. The percent of specimens tested positive for influenza includes all specimens tested positive for seasonal or pandemic influenza. The pie charts show the distribution of virus subtypes among all specimens that were tested positive for influenza. The available country data were joined in larger geographical areas with similar influenza transmission patterns to be able to give an overview (http://www.who.int/csr/disease/swineflu/transmission_zones/en)

Qualitative indicators (Week 29, 2009 to Week 26, 2010: 13 July 2009 - 3 July 2010)

The qualitative indicators monitor: the global geographic spread of influenza, trends in acute respiratory diseases, the intensity of respiratory disease activity, and the impact of the pandemic on health-care services.

The maps below display information on the qualitative indicators reported. Information is available for approximately 60 countries each week. Implementation of this monitoring system is ongoing and completeness of reporting is expected to increase over time.

Geographic spread of influenza activity
Trend of respiratory diseases activity compared to the previous week
Intensity of acute respiratory diseases in the population
Impact on health care services
Laboratory-confirmed cases of pandemic (H1N1) 2009 as officially reported to WHO by States Parties to the IHR (2005) as of 11 July 2010

The countries and overseas territories/communities that have newly reported their first pandemic (H1N1) 2009 confirmed cases since the last web update (No. 108): none.

The countries and overseas territories/communities that have newly reported their first deaths among pandemic (H1N1) 2009 confirmed cases since the last web update (No. 108): none.

*The reported number of fatal cases is an under representation of the actual numbers as many deaths are never tested or recognized as influenza related

**No update since 7 March 2010

***No update since 23 May 2010

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