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Published Date: 2012-11-09 22:35:27
Subject: PRO/AH/EDR> Influenza (104): WHO update
Archive Number: 20121109.1402543

INFLUENZA (104): WORLD HEALTH ORGANISATION UPDATE
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Date: Fri 9 Nov 2012
Source: World Health Organisation (WHO), Surveillance and Monitoring, Influenza Update [edited]
http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance/en/

Influenza update number 172
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Summary
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- Many countries of the Northern Hemisphere temperate region reported increasing detections of influenza viruses, particularly in North America and Western Europe, however none have crossed their seasonal threshold for ILI/ARI [influenza-like illness/acute respiratory disease] consultation rates.
- Several countries in the tropical areas experienced active transmission of influenza virus in recent weeks. In the Americas, Nicaragua and Costa Rica reported mainly influenza B virus detections. In Asia, India, Sri Lanka, Nepal, and Cambodia are all reporting a mixture of all 3 virus subtypes.
- In Sub-Saharan Africa, Cameroon and Ethiopia have reported an increase in influenza virus detections.
- Influenza activity in the temperate countries of the Southern Hemisphere is at inter-seasonal levels. A review of the 2012 southern hemisphere influenza season was published in the Weekly Epidemiological Record (WER) 2 Nov 2012, vol. 87, 44 (pp. 421-436) http://www.who.int/wer/2012/wer8744.pdf.

Countries in the temperate zone of the northern hemisphere
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Many countries of the temperate regions of the Northern Hemisphere reported increasing numbers of detections of influenza, however, none have yet crossed their seasonal thresholds for ILI/ARI consultations rates and numbers of influenza virus detections are still low.

North America

In Canada, the national rate of influenza-like illness [ILI] remained low however there has been a slight increase in the number of influenza virus detections. In addition, 2 influenza outbreaks were reported in long term care facilities and 5 influenza associated hospitalizations in persons over 65 years. Influenza A accounted for 22 of 25 influenza viruses detection and all of the type A viruses with subtype information were influenza A(H3N2).

In the United States of America, ILI consultation rates are at 1.2 percent, [which is] below the seasonal threshold (2.2 percent). Many states are yet to report any influenza activity but 33 states have reported sporadic detections. Of 3036 specimens tested in late October [2012], 188 (6.2 percent) were positive for influenza virus. Among the positive influenza samples, 58 percent were influenza A and 97 percent of those were influenza A(H3N2).

Europe

Although overall influenza circulation remained low and below thresholds, there were reports of increasing ILI activity in Armenia, Israel, Poland, the Republic of Moldova and western Russia. Sporadic virus detections were reported in the Czech Republic, Denmark, France, Lithuania, Norway, regions of Russia, Sweden and the United Kingdom.

Northern Asia

Northern China continued to report very low influenza activity, while in Mongolia, ILI activity has increased particularly in Dornod and Selenghe provinces. However, the large majority of viruses detected in Mongolia in October were respiratory viruses other than influenza.

Number of specimens positive for influenza by subtype in the Northern Hemisphere
http://gamapserver.who.int/gareports/Default.aspx?ReportNo=5&Hemisphere=Northern

Countries of the tropical zone
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Tropical countries of the Americas

Influenza type B transmission has been noted in some countries of Central America and the Caribbean in recent weeks but is generally at low levels.

El Salvador, Costa Rica, and Nicaragua reported continued low level transmission of influenza type B, with smaller numbers of A(H3N2), following a peak of influenza B transmission in late August. In the Caribbean, Jamaica has reported recent transmission of influenza B whilst in Cuba, numbers of influenza A(H1N1)pdm09 detections have increased slightly over several weeks following a peak influenza B transmission in June. Epidemics of bronchiolitis have been noted in Guadeloupe and Martinique along with an increase of respiratory syncytial virus (RSV) in Martinique.

In the tropical zone of South America, influenza activity continues to decline with low numbers of virus detections being reported. Influenza activity in Brazil appears overall to be decreasing with both influenza B and influenza A(H3N2) reported at low levels. Since the beginning of 2012, influenza viruses were detected in 21 percent (3900/18700) of SARI cases in Brazil. Of these, 66 percent (2588/3900) were influenza A(H1N1)pdm09. Peru has reported low levels of mainly influenza B virus whilst in Paraguay, both influenza B and influenza A(H3N2) viruses have been reported.

Number of specimens positive for influenza by subtype in the tropical South America transmission zone
http://gamapserver.who.int/gareports/Default.aspx?ReportNo=5&Hemisphere=Southern.

Sub-Saharan Africa

Cameroon and Ethiopia have reported increasing transmission of influenza A(H3N2) since the last report. Kenya continued to report low circulation of mainly influenza B.

Tropical Asia

In tropical Asia, India, Sri Lanka, Cambodia and Nepal continued to report a mixture of influenza B and influenza A(H1N1)pdm09 circulation.

In India, influenza activity has decreased since peaking in mid-September. Influenza A(H1N1)pdm09 has been the most common virus detected throughout the season though it has been only slightly more common than influenza type B. Sri Lanka and Thailand experienced a similar pattern of transmission, however, influenza A(H3N2) has become increasingly detected since early October in Sri Lanka. Nepal is reporting increasing influenza activity, with mainly influenza B in circulation. In southern China, influenza activity is at inter-seasonal levels, with some influenza A(H3N2) being reported.

In South East Asia, Cambodia, Lao PDR and Viet Nam have all reported recent transmission of influenza virus but with differences in the most commonly detected type or subtype. Cambodia has reported influenza A(H3N2) almost exclusively since early September [2012], while Lao PDR has reported a mixture of influenza A(H1N1)pdm09 and influenza A(H3N2) and Viet Nam a predominance of type B with lesser amounts of A(H3N2).

Countries in the temperate zone of the southern hemisphere
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Influenza activity has continued to decline in all temperate countries of the southern hemisphere and is now at inter-seasonal levels.

Temperate countries of southern Africa

In South Africa, influenza activity is now at inter-seasonal levels, with only influenza B in circulation at very low levels. Zambia however, has reported sporadic cases of influenza A(H3N2) and influenza B viruses.

Oceania, Melanesia and Polynesia

Australia and New Zealand have finished their reporting for the influenza 2012 season.

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[The Library of Weekly WHO Flu charts is available at:
http://www.who.int/influenza/gisrs_laboratory/flunet/charts/en/index.html.

Of interest also is the the Weekly Epidemiological Record Review of the 2012 southern hemisphere influenza season, available at: WER 2 Nov 2012, vol. 87, 44 (pp. 421-436
http://www.who.int/wer/2012/wer8744.pdf.

The EuroFlu Weekly Electronic Bulletin similarly reported on 9 Nov 2012 that:
"Levels of influenza activity in the European Region Region remain low, with only a few countries reporting sporadic influenza detections. The influenza positivity rate has been stable; since the start of the season, A(H1N1)pdm09, A(H3N2) and type B viruses have circulated in approximately equal proportions, based on detections and sub-typing of representative type A specimens from both sentinel and non-sentinel sources. The number of hospitalizations due to severe acute respiratory infection (SARI) is stable, and none of the cases reported so far was associated with laboratory-confirmed influenza (http://www.euroflu.org/cgi-files/bulletin_v2.cgi).

The 2012/2013 influenza season in the Northern Hemisphere has yet to unsheathe its claws. - Mod.CP]

See Also