Pandemic (H1N1) 2009 - update 69

Weekly update

As of 4 October 2009, worldwide there have been more than 375,000 laboratory confirmed cases of pandemic influenza H1N1 2009 and over 4500 deaths reported to WHO.

As many countries have stopped counting individual cases, particularly of milder illness, the case count is significantly lower than the actually number of cases that have occurred. 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 data.

In the temperate regions of the Northern Hemisphere, transmission of influenza virus and rates of influenza-like-illness (ILI) continue to increase marking an unusually early start to fall and winter influenza season in many countries. Geographically widespread influenza is being reported throughout North America, with the United States reporting ILI levels elevated above the seasonal baseline for the past month and Mexico reporting a high intensity of respiratory diseases for the past three weeks. In Canada, although overall ILI activity remains low, focal increases have been reported in the western part of Canada. In Europe and Central and Western Asia, early transmission of influenza virus continues to increase in many countries, with more intense focal activity being reported in a few. National or regional ILI levels remained elevated above the baseline in parts of the United Kingdom (Northern Ireland and Scotland), Ireland, and Israel. In Ireland, a high intensity of respiratory diseases has been reported for the past two weeks, with the highest rates of ILI reported among children aged 5-14 years old. In addition to Ireland and Israel, widespread geographic spread of influenza virus is also now being reported in Belgium, the Netherlands, and Cyprus. At least 10 countries in the region are also reporting an increasing trend in respiratory diseases activity. In Japan, influenza activity continues to be elevated above the seasonal epidemic threshold since week 33, most recently in the large population centers.

In the tropical regions of the Americas and Asia, influenza virus transmission persists, however influenza activity remained variable. Geographically widespread to regional influenza activity continues to be reported throughout the tropical region of the Americas without a consistent overall trend (and increasing trend in parts of the Caribbean, and decreasing in much of tropical Central and South America). High intensity respiratory diseases activity was reported in Columbia, Cuba, and El Salvador, and moderate healthcare impact was experienced in many countries; two countries, Barbados and St. Lucia, reported severe healthcare impact. As influenza transmission slowly declines in many parts of South and Southeast Asia, several countries are reporting geographically regional spread (India, Bangladesh, and Thailand) or localized spread (Sri Lanka and Myanmar) of influenza activity; and most countries in the region have reported experiencing a low health care impact since late September.

In the temperate regions of the southern hemisphere, influenza transmission has largely subsided (Chile, Argentina, and New Zealand) or continues to decline substantially (South Africa and Australia).

All pandemic H1N1 2009 influenza viruses analyzed to date have been antigenically and genetically similar to A/California/7/2009-like pandemic H1N1 2009 virus. See below for a detailed laboratory surveillance update.

Qualitative indicators (Week 29 to Week 39: 13 July - 27 September 2009)

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 during weeks 29 to 39. 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 4 October 2009

The countries and overseas territories/communities that have newly reported their first pandemic (H1N1) 2009 confirmed case(s) since the last web update (No. 68) as of 4 October 2009 are:

Tajikistan.

*Given that countries are no longer required to test and report individual cases, the number of cases reported actually understates the real number of cases.