Influenza

Influenza update - 20 October 2010

Introduction

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), FluID 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.

Description: Displayed data reflect the most recent information reported to 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 all influenza subtypes. 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 (Influenza transmission zones)with similar influenza transmission patterns in order to present an overview

Influenza - Update 119

20 October 2010 - Summary:

Influenza activity in the temperate regions of the Southern Hemisphere is continuing to decline. In most of the temperate regions of the Northern Hemisphere the level of activity is still low. Influenza virus A(H3N2) continues to be the most frequently detected virus world wide. Most of the influenza A(H3N2) viruses are A/Perth/16/2009-like,which is the virus strain included in the seasonal vaccines for the Northern and Southern Hemispheres.

Southern hemisphere temperate countries

This winter's influenza season in the temperate countries in the southern hemisphere has peaked and is declining in most areas.

New Zealand's influenza activity has decreased since late August and is now under baseline for the third consecutive week. The most common influenza virus detected this season in New Zealand is H1N1 (2009). In Australia the influenza surveillance indicated an increase in the activity in the last week of September, Australia has had a co-circulation of mainly H1N1 (2009) and influenza B.

In the southern cone of South America, Chile continues to report high transmission of influenza but since mid September the activity has declined. The predominant virus circulating in Chile has been A(H3N2) with co-circulation of H1N1 (2009) in lower numbers. Detections of other respiratory viruses such as respiratory syncytial virus are also declining. Argentina and Uruguay have both had a season with mostly influenza type B, and are now reporting a decrease in number of virus detections.

In South Africa influenza activity continues to decline, after a season where the majority of the laboratory confirmed cases were influenza type B, but with co-circulation of influenza A(H3N2) and smaller numbers of H1N1 (2009).

Tropical zone

In the tropical areas of the world most countries are reporting decreased influenza activity, but some countries in Southeast Asia, Central and South America are experiencing an increase in transmission intensity due to mainly influenza A(H3N2).

In Central America influenza activity is declining, with influenza A(H3N2) being the most frequently reported virus since August 2010. In the Caribbean, Jamaica is reporting an increased number of severe acute respiratory infections (SARI) with influenza A(H3N2) being the most predominant virus detected . Mexico had an earlier start than normal for the influenza season, with most of the viruses being influenza A(H3N2). The activity peaked in August-September and both influenza like-illness (ILI) and severe acute respiratory disease (SARI) are still declining.

In South America, Colombia is currently reporting increased influenza activity due to mainly A(H3N2) viruses, with co-circulation of H1N1 (2009) and some influenza B.

In South Asia, India's country-wide outbreak of mainly H1N1 (2009) has peaked and there is now a lower incidence of new cases and deaths in all regions being reported.

In South East Asia, neighboring countries Thailand and Cambodia are currently reporting an increased number of influenza virus detections. In Thailand influenza H1N1 (2009) viruses are dominating but there is also an increasing number of influenza A(H3N2) detections and a lower number of influenza B. In Cambodia influenza A(H3N2) is the predominant influenza virus circulating.

In China, Hong Kong Special Administrative Region the sentinel surveillance system for general practitioners shows a decreasing ILI activity during the last weeks.

African countries in the tropical zone are reporting on low influenza activity. Low numbers of H1N1 (2009) viruses were detected in West Africa. Low but sustained transmission of seasonal A (H3N2) continues to be reported from eastern Africa, notably from Kenya. Data from Cameroon and Central African Republic shows sporadic influenza type B, A(H3N2) and H1N1 (2009) activity in the central African region.

Northern hemisphere temperate countries

China is reporting declining influenza virus activity in both the Northern and Southern region. Since mid August, both regions have had predominantly influenza A(H3N2).

Northern America still has low influenza activity. Canada had a slight increase in ILI activity, together with a small increase in the proportion of positive influenza specimens, mainly influenza A(H3N2) viruses. In the U.S. ILI activity is below baseline in all regions.

The European Region is still reporting low levels of influenza activity, with sporadic detections of influenza A(H3N2), H1N1 (2009) and influenza B.

FluNet reports

During weeks 39 to 40 (26 September - 9 October), National Influenza Centres (NICs) from 35 countries reported data to FluNet*. A total of 2,415 specimens were reported as positive for influenza viruses, 2,167 (89.7%) were typed as influenza A and 248 (10.3%) as influenza B. Of the sub-typed influenza A viruses reported, 15.5% were influenza H1N1 (2009) and 84.5 % were influenza A(H3N2). See below for country-specific data.

  • Influenza H1N1 (2009): Australia, Cambodia, Chile, China, Hong Kong SAR, Ghana, Iran (Islamic Republic of), Japan, Kenya, Madagascar, New Zealand, Nigeria, Senegal, Singapore, South Africa, Switzerland, Thailand and United States of America.
  • Influenza A(H3N2): Australia, Bangladesh, Cambodia, Cameroon, Chile, China, Hong Kong SAR, French Guiana, Ghana, Jamaica, Japan, Kenya, Madagascar, Mexico, New Zealand, Singapore, South Africa, Thailand, United Republic of Tanzania and United States of America.
  • Influenza B: Australia, Cambodia, Cameroon, Chile, China, Hong Kong SAR, Honduras, Iran (Islamic Republic of), Singapore, South Africa, Switzerland, Thailand and United States of America.

Algeria, Belgium, Denmark, Estonia, Ethiopia, Finland, France, Greece, Netherlands, Norway, Poland, Russian Federation, Rwanda, Slovenia, Tunisia and United Kingdom reported no influenza activity.

* Some NICs report to FluNet retrospectively leading to updates of previous summary data.

Qualitative indicators

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.

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