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Influenza update - 20 May 2011 (WHO, edited)
[Source: World Health Organization, full page: (LINK).]
Influenza update - 20 May 2011
Update number 134
Summary
? The influenza season is largely finished in the temperate countries of the northern hemisphere with transmission now either undetectable or at very low levels in most areas.
? A few tropical countries are experiencing low grade transmission including the Dominican Republic, Venezuela (influenza A(H1N1)2009) and Jamaica (influenza type B) in the Americas, Rwanda (influenza A(H3N2) and Madagascar (influenza type B) in Sub-Saharan Africa.
? The influenza season has not yet started in the temperate countries of the southern hemisphere. Australia has reported a small increase in reports of influenza-like illness however actual detections of influenza virus have decreased in most jurisdictions in recent weeks, including in the northern tropical states.
? A summary review of the northern hemisphere 2010/11 winter influenza season will be published in the World Health Organization's Weekly Epidemiological Record on May 26, 2011.
Countries in the temperate zone of the northern hemisphere
North America:
North America circulation of influenza viruses (snapshot) pdf, 99kb
Influenza activity in both the United States of America (USA) and Canada has now largely returned to baseline levels.
Rates of influenza-like illness (ILI), reports of influenza related deaths, and influenza related hospitalizations all continue to decrease in both countries, though some localized activity persists in the Canadian provinces of Nova Scotia and Newfoundland.
The percentage of respiratory specimens testing positive for influenza virus is low, 5% in Canada and less than 2% in the USA, and are predominantly influenza type B.
Europe, North Africa and the Middle East:
Influenza activity across Europe and northern Africa has also returned to very low levels.
Consultations for ILI and acute respiratory infection (ARI) are at very low levels in Europe and half of countries reported no influenza activity. Only 2% and 4% of respiratory samples tested positive for influenza from sentinel ILI and severe acute respiratory infection (SARI) cases, respectively, in Europe.
Little or no influenza activity is being detected in reporting countries of North Africa and the Middle East.
Of the small numbers of viruses being detected in Europe, North Africa and the Middle East, influenza type B is the most common type.
Northern Asia:
Eastern Asia circulation of influenza viruses (snapshot) pdf, 108kb
No notable influenza activity is being reported from Mongolia, northern China, the Republic of Korea or Japan.
Rates of ILI and detections of influenza viruses are all quite low; 3% of all outpatient visits were due to ILI in northern China, which is below that observed in the previous three seasons.
Most influenza viruses detected in the area are influenza type B (all 12 viruses in northern China and 60% of 415 viruses in Japan).
Countries in the tropical zone
Very little influenza activity is being reported across the tropical regions. In the Americas, the Dominican Republic has been reporting low numbers of influenza A(H1N1)2009 for the last five weeks.
Jamaica has also experienced low numbers of persistent influenza type B transmission for several weeks, though in both of these countries numbers have recently decreased.
Previously noted influenza A(H1N1)2009 circulation in Venezuela peaked in late march and has now returned to very low levels.
Several countries in the tropical areas of Central and South America are now reporting an increase of respiratory infection activity related to respiratory syncytial virus transmission.
In Sub-Saharan Africa, the previously reported transmission of influenza A(H1N1)2009 and influenza type B in Ghana and Kenya is subsiding.
Rwanda has experienced recent active transmission of influenza A(H3N2) over the past 10 to 12 weeks and Madagascar reports persisting transmission of primarily influenza type B with fewer numbers of H3N2.
In tropical areas of Asia, very low numbers of influenza viruses are being reported with below baseline rates of ILI, where these data are available.
Countries in the temperate zone of the southern hemisphere
Southern hemisphere circulation of influenza viruses (snapshot) pdf, 116kb
The influenza season has not yet started in the temperate countries of the southern hemisphere.
Australia, which had previously observed higher than expected numbers of influenza virus detections, most notably in the northern states of Queensland and the Northern Territories, reports that detections of virus have been decreasing in most jurisdictions in recent weeks.
ILI reports in Australia have increased slightly but are still low.
The majority of virus detections in Australia over the summer have been H3N2, though in the past one week H1N1 (2009) and influenza type B have become relatively more common.
Source of data
The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks.
The updates are based on available epidemiological and virological data sources, including FluNet (reported by the Global Influenza Surveillance Network) and influenza reports from WHO Regional Offices and Member States. Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.
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Update number 134
Summary
? The influenza season is largely finished in the temperate countries of the northern hemisphere with transmission now either undetectable or at very low levels in most areas.
? A few tropical countries are experiencing low grade transmission including the Dominican Republic, Venezuela (influenza A(H1N1)2009) and Jamaica (influenza type B) in the Americas, Rwanda (influenza A(H3N2) and Madagascar (influenza type B) in Sub-Saharan Africa.
? The influenza season has not yet started in the temperate countries of the southern hemisphere. Australia has reported a small increase in reports of influenza-like illness however actual detections of influenza virus have decreased in most jurisdictions in recent weeks, including in the northern tropical states.
? A summary review of the northern hemisphere 2010/11 winter influenza season will be published in the World Health Organization's Weekly Epidemiological Record on May 26, 2011.
Countries in the temperate zone of the northern hemisphere
North America:
North America circulation of influenza viruses (snapshot) pdf, 99kb
Influenza activity in both the United States of America (USA) and Canada has now largely returned to baseline levels.
Rates of influenza-like illness (ILI), reports of influenza related deaths, and influenza related hospitalizations all continue to decrease in both countries, though some localized activity persists in the Canadian provinces of Nova Scotia and Newfoundland.
The percentage of respiratory specimens testing positive for influenza virus is low, 5% in Canada and less than 2% in the USA, and are predominantly influenza type B.
Europe, North Africa and the Middle East:
Influenza activity across Europe and northern Africa has also returned to very low levels.
Consultations for ILI and acute respiratory infection (ARI) are at very low levels in Europe and half of countries reported no influenza activity. Only 2% and 4% of respiratory samples tested positive for influenza from sentinel ILI and severe acute respiratory infection (SARI) cases, respectively, in Europe.
Little or no influenza activity is being detected in reporting countries of North Africa and the Middle East.
Of the small numbers of viruses being detected in Europe, North Africa and the Middle East, influenza type B is the most common type.
Northern Asia:
Eastern Asia circulation of influenza viruses (snapshot) pdf, 108kb
No notable influenza activity is being reported from Mongolia, northern China, the Republic of Korea or Japan.
Rates of ILI and detections of influenza viruses are all quite low; 3% of all outpatient visits were due to ILI in northern China, which is below that observed in the previous three seasons.
Most influenza viruses detected in the area are influenza type B (all 12 viruses in northern China and 60% of 415 viruses in Japan).
Countries in the tropical zone
Very little influenza activity is being reported across the tropical regions. In the Americas, the Dominican Republic has been reporting low numbers of influenza A(H1N1)2009 for the last five weeks.
Jamaica has also experienced low numbers of persistent influenza type B transmission for several weeks, though in both of these countries numbers have recently decreased.
Previously noted influenza A(H1N1)2009 circulation in Venezuela peaked in late march and has now returned to very low levels.
Several countries in the tropical areas of Central and South America are now reporting an increase of respiratory infection activity related to respiratory syncytial virus transmission.
In Sub-Saharan Africa, the previously reported transmission of influenza A(H1N1)2009 and influenza type B in Ghana and Kenya is subsiding.
Rwanda has experienced recent active transmission of influenza A(H3N2) over the past 10 to 12 weeks and Madagascar reports persisting transmission of primarily influenza type B with fewer numbers of H3N2.
In tropical areas of Asia, very low numbers of influenza viruses are being reported with below baseline rates of ILI, where these data are available.
Countries in the temperate zone of the southern hemisphere
Southern hemisphere circulation of influenza viruses (snapshot) pdf, 116kb
The influenza season has not yet started in the temperate countries of the southern hemisphere.
Australia, which had previously observed higher than expected numbers of influenza virus detections, most notably in the northern states of Queensland and the Northern Territories, reports that detections of virus have been decreasing in most jurisdictions in recent weeks.
ILI reports in Australia have increased slightly but are still low.
The majority of virus detections in Australia over the summer have been H3N2, though in the past one week H1N1 (2009) and influenza type B have become relatively more common.
Source of data
The Global Influenza Programme monitors influenza activity worldwide and publishes an update every two weeks.
The updates are based on available epidemiological and virological data sources, including FluNet (reported by the Global Influenza Surveillance Network) and influenza reports from WHO Regional Offices and Member States. Completeness can vary among updates due to availability and quality of data available at the time when the update is developed.
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