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Published Date: 2013-01-07 21:59:51
Subject: PRO/EDR> Influenza (04): WHO update
Archive Number: 20130107.1486115

INFLUENZA (04): WHO UPDATE
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Date: Fri 4 Jan 2013
Source: WHO Surveillance and Monitoring, Influenza updates [edited]
http://www.who.int/influenza/surveillance_monitoring/updates/2013_01_07_surveillance_update_176.pdf

Influenza update no 176
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Summary
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- Reporting of influenza activity has been irregular in the past 2 weeks due to the holiday season in many countries. As a result, overall virus detections reported have dropped off although in most countries in the northern temperate regions, influenza activity appears to have continued rising.
- Many countries of North America, Europe, North Africa, Eastern Mediterranean, and temperate Asia have reported increasing influenza activity over the past weeks. North China has started its influenza season.
- In tropical Asia, influenza activity was similar to previous weeks, with persistent low-level circulation.
- Influenza activity in sub-Saharan Africa has declined in most countries, with the exception of the Democratic Republic of Congo and Ghana.
- In the Caribbean, Central America, and tropical South America, influenza activity decreased to low levels, except for Bolivia, where there is increasing circulation of influenza A(H3N2).
- Influenza activity in countries of the southern hemisphere is currently at inter-seasonal levels.
- Several unconfirmed media stories have reported a number of deaths related to infection with influenza A(H1N1)pdm09 in different parts of the world [such as in report [2] below]. As with other seasonal influenza viruses, it is expected that some deaths would occur with infection, in particular now, when influenza season starts in the northern hemisphere. These reports at times refer to this A(H1N1)pdm09 virus as "swine flu", causing some confusion with other viruses recently reported in the United States. A(H1N1)pdm09 virus has been circulating in humans for more than 3 years and now is a seasonal human influenza virus.

Countries in the temperate zone of the northern hemisphere
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North America
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Influenza activity in North America has increased sharply since the last report with Canada and the United States both reporting widespread transmission of influenza. Influenza activity in Canada continued to rise with increases in all indicators in the last 2 weeks.
The influenza-like illness (ILI) consultation rate increased from 4 percent at the time of the previous report to 6.6 percent, with the highest rate observed in children less than 5 years old, followed by 5-19 year olds. The percentage of samples that tested positive for influenza also increased from 17.8 percent to 31.1 percent. In the last 2 weeks, 127 new influenza outbreaks were reported: 87 in long-term-care facilities, 9 in hospitals, 1 in a school, and 30 in other facilities or communities. This represents a marked increase from the previous report of 22 outbreaks. 241 laboratory confirmed influenza associated hospitalizations were reported in 5 provinces; 97 percent (236/241) were influenza A, of which, half (117/236) were sub-typed. Of those with subtype information, 97.5 percent (114/117) were influenza A(H3N2) and 1.5 percent (3/117) were A(H1N1)pdm09. Just over half of these cases (51 percent, 123/241) were aged 65 years or older. 16 influenza associated deaths were reported in the last 2 weeks of 2012; all with influenza A. Influenza A continued to predominate in Canada, with very few detections of influenza B. Of the respiratory specimens that were positive for influenza in the previous reporting week, 97.7 percent (4525/4632) were positive for influenza A, and 2.3 percent (107/4632) for influenza B. Of the influenza A viruses that were sub-typed, 97.4 percent (1164/1195) were A(H3N2) and 2.6 percent (31/1195) were A(H1N1)pdm09. Since the start of the season, the National Microbiology Laboratory has antigenically characterized 177 influenza viruses (136 A(H3N2), 17 A(H1N1)pdm09, and 24 influenza B). The 136 influenza A(H3N2) viruses were antigenically similar to the vaccine virus A/Victoria/361/2011. The 17 A(H1N1)pdm09 viruses were antigenically similar to the vaccine virus A/California/07/09. Among the influenza B viruses, 20 were antigenically similar to the vaccine virus B/Wisconsin/01/2010 (Yamagata lineage) and 4 were similar to B/Brisbane/60/2008 (Victoria lineage; component of the previous 2011-2012 seasonal influenza vaccine). None of the viral samples tested were resistant to the neuraminidase inhibitors oseltamivir (n=128) or zanamivir (n=127).

In the USA, the majority of influenza viruses detected were A(H3N2), however influenza B accounted for a larger proportion than in Canada. Of the 2961 influenza positive specimens in the last week of 2012, 79 percent were influenza A and 21 percent were influenza B. Of the influenza A viruses with sub-type information, 98 percent were A(H3N2). Since 1 October 2012, the CDC has antigenically characterized 413 influenza viruses. All 17 A(H1N1)pdm09 viruses tested were characterized as A/California/7/2009-like and 99.3 percent of the 279 A(H3N2) influenza viruses tested were A/Victoria/361/2011-like. Of the 115 influenza B viruses characterized 69 percent were B/Wisconsin/1/2010-like of the Yamagata lineage, the B virus component of this season's trivalent influenza vaccine, and 31 percent were of the Victoria lineage.
Since 1 Oct [2012], none of the 526 A(H3N2), 39 A(H1N1)pdm09, or 226 B viruses have been resistant to neuraminidase inhibitors.

No new human infections of novel influenza A virus were reported in the last week. A total of 312 infections with variant influenza viruses have been reported from 11 states since July 2012. More information about H3N2v infections can be found at http://www.cdc.gov/flu/swineflu/h3n2v-outbreak.htm.

Europe
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Influenza activity in the Europe has increased, mainly in the northern and western part of the continent. Growing numbers of countries in different parts of the region reported increasing detections of influenza viruses, though overall reporting was reduced due to the holiday season. The European Centre for Disease Prevention and Control (ECDC) announced the start of the influenza season from the last week of November [2012] for the countries of the European Union and the European Economic Area (EU/EEA).

In EU/EEA countries, 25.3 percent of clinical samples were positive for influenza virus, a slight reduction from the previous week. The distribution of viruses types and subtypes in Europe was notably different from that observed in North America. Throughout Europe, since the beginning of the season, influenza A accounted for about 60 percent of influenza viruses detected and influenza B, 40 percent. However in contrast to North America, of the influenza A viruses that were subtyped, 51 percent (655/1293) were A(H3N2) and 49 percent (638/1293) were A(H1N1)pdm09. In the last week of December [2012], influenza A(H1N1)pdm09 increased in proportion, relative to A(H3N2), making up 72 percent (139/194) of influenza A viruses from sentinel sources with subtype information in that week.

In the last week of December 2012, 4 countries (France, Italy, the Netherlands, and Norway) reported medium intensity transmission. Previously this season, only France and Luxembourg had reported medium activity 2 weeks ago, and no countries had reported medium activity before that. The geographic spread of influenza activity was reported as widespread by Belgium, Denmark, France, Norway, and the UK (England), regional by Italy, the Netherlands, and the United Kingdom (Scotland), and sporadic by Estonia, Greece, Lithuania, and Spain. Prior to the last 2 weeks, no countries had reported widespread activity.

Sentinel SARI hospitalization rates that were positive for influenza also increased with 42 laboratory-confirmed cases in 4 countries (Belgium, France, Ireland, and the United Kingdom).

Since the end of September [2012], 7 countries (Denmark, England, Germany, Latvia, Portugal, Romania, and Switzerland) have antigenically characterized 81 influenza viruses; 6 were A(H1N1)pdm09 A/California/7/2009 (H1N1)-like, 52 A(H3N2) A/Victoria/361/2011-like, 15 B/Wisconsin/1/2010-like (Yamagata lineage, and 8 B/Brisbane/60/2008-like (Victoria lineage). None of the 28 A(H1N1)pdm09, 37 A(H3N2), and 16 B viruses tested in that period were resistant to the neuraminidase inhibitors, oseltamivir and zanamivir.

Northern Africa and the eastern Mediterranean region
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Increasing influenza activity has been noted in North Africa and the Middle East. Bahrain and Jordan reported increasing circulation of influenza A(H1N1)pdm09, and Iran, Oman, and Qatar have detected influenza A(H1N1)pdm09 and influenza B. Pakistan detected increasing levels of A(H3N2) and influenza B, while all 3 virus sub-types were in circulation in Algeria.

Temperate Asia
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Influenza activity remained at low levels throughout the temperate region of Asia, however, ILI activity has increased for the 5th consecutive week in northern China. The proportion of outpatient visits at sentinel surveillance sites that were due to ILI increased to 3.9 percent compared to 3.2 percent in the previous report. China has officially announced the start of the influenza season in northern China. 4 outbreaks were reported in the previous week, in Shanxi and Hubei Provinces, and there were no deaths attributed to acute respiratory infections. Influenza A accounted for 98 percent (188/192) of influenza viruses detected; 2 percent (4/192) were influenza B. Of the influenza A that were sub-typed, 81 percent were A(H3N2) and 19 percent were A(H1N1)pdm09. Among influenza viruses antigenically characterized by the Chinese National Influenza Center since October 2012, 198 (100 percent) influenza A(H3N2) viruses are related to A/Victoria/361/2011(H3N2)-like; 69 (95.8 percent) influenza B/Victoria viruses are related to B/Brisbane/60/2008-like; 6 (100 percent) influenza B/Yamagata viruses are related to B/Wisconsin/01/2010- like. None of the influenza samples tested were resistant to the neuraminidase inhibitors, oseltamivir and zanamivir.

In Mongolia, influenza activity increased, due to influenza A(H3N2). Although ILI activity increased on the whole, there were marked inter-regional differences, with Selnghe and Dornod provinces reporting the highest rates. While most ILI in recent weeks was associated with other respiratory viruses such as respiratory syncytial virus, rhinovirus, and human coronaviruses, the increase in influenza positive samples in the last week accounted for approximately half of the ILI samples tested.

Influenza activity remained low in both Japan and the Republic of Korea, however, there is some evidence of increasing activity, with detections of influenza A(H3N2) in Japan, and A(H3N2) and A(H1N1)pdm09 in the Republic of Korea.

Countries in the tropical zone
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Tropical countries of the Americas
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In both central America and the Caribbean, detections of influenza declined to low levels from their peaks in late summer. Influenza A(H3N2) and influenza B were the most widely detected sub-types, with the exception of Cuba, which reported A(H1N1)pdm09.

Influenza activity throughout the tropical zone of south America continued to decline with low numbers of virus detections being reported in all countries, except the Plurinational State of Bolivia, which reported increasing circulation of influenza A(H3N2). Influenza A(H3N2) and influenza B were the most widely reported sub-types throughout the region.

Sub-Saharan Africa
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Most countries in Sub-Saharan Africa experienced decreasing detections of influenza virus. However, Ghana continued to report circulation of predominantly influenza A(H1N1)pdm09 while in the Democratic Republic of Congo, there is increasing influenza activity from mainly influenza A(H1N1)pdm09. Zambia and Madagascar are also reporting low-level detections of influenza B virus.

Tropical Asia
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Influenza activity in most countries of south east Asia has remained similar to previous weeks, with continuing low-level circulation in Cambodia, Lao PDR, Sri Lanka, Thailand, and Viet Nam.

India continued to report declining influenza positive samples from its peak in mid-September [2012] of mainly A(H1N1)pdm09, and is now at inter-seasonal levels. Sri Lanka reported persistent circulation of all 3 influenza sub-types, while A(H3N2) and influenza B viruses were detected in Cambodia and Thailand. Similar to previous weeks, transmission of predominantly influenza B virus was reported in Viet Nam.

Influenza activity in Singapore and southern China, including Hong Kong SAR, remained below seasonal thresholds. In Singapore and southern China, half of the influenza virus positive samples were A(H3N2), and in Hong Kong SAR, 62 percent (28/45) were attributed to influenza A(H1N1)pdm09, and 4 percent influenza B. In southern China, influenza B detections increased.

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

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[The original text should be accessed via the source URL above to view the several figures accompanying the foregoing text.

See also the following graphical information obtained from the Global Influenza Surveillance and Response System (GISRS):
1. Northern hemisphere -- Number of specimens positive by subtype:
http://gamapserver.who.int/gareports/Default.aspx?ReportNo=5&Hemisphere=Northern
2. Southern hemisphere -- Number of specimens positive by subtype:
http://gamapserver.who.int/gareports/Default.aspx?ReportNo=5&Hemisphere=Southern.

Previously the identity of the influenza virus responsible for the outbreak of influenza in the Palestinian Territories (West Bank) was queried in ProMED-mail. In fact, as indicated in the preceding update, the H1N1 virus is likely to be the A(H1N1)pdm09 strain, which has replaced the previously circulating H1N1 human strain (incorrectly designated 'swine flu')

The Sun 6 Jan 2013 edition of World Bulletin (http://www.worldbulletin.net/?aType=haber&ArticleID=101324) states that: "The swine flu death toll has risen to 14 in the West Bank. A child and woman have died after contracting swine flu in the northern West Bank, bringing the death toll this winter [2012-13] to 14, the Palestinian health ministry said on Sunday [6 Jan 2012].

Health official Asaad al-Rimlawi said all those who died from the H1N1 virus [infection] had low immune systems. Many of the 365 Palestinians who are being treated for virus have recovered and are in good health, he said.

The ministry said on Friday [4 Jan 2013] that H1N1 cases had also been recently recorded in Jordan, Turkey, Saudi Arabia, and Yemen." - Mod.CP]

See Also