Update 177 final - WHO · Influenza Update N° 177 ... zed children zed children S, the major B accounte sitive for influ B. Of the in C ested were ested were A isconsin/1/ l influenza

Influenza update | 18 January 2013 1

Influenza Update N° 177 18 January 2013

Summary

Influenza activity in North America remained high with some indications that activity might have peaked in areas. Some but not all indicators of severity in the United States of America and Canada have been slightly higher than in previous recent seasons. The onset of the season was earlier than usual and coincided with circulation of other respiratory viruses. Influenza A(H3N2) predominates in North America with A(H1N1)pdm09 being uncommon.

Many countries in Europe and temperate Asia are reporting increasing influenza activity with A(H1N1)pdm09 being relatively more prominent in Europe than in North America.

Some countries in the Eastern Mediterranean and the North Africa have reported declining detections of influenza positive samples. Influenza A(H1N1)pdm09 is predominant in the region.

In tropical Asia, the influenza activity is similar to previous weeks, with persistent low-level circulation.

Influenza activity in sub-Saharan Africa has declined in most countries

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 in countries of the southern hemisphere are currently at inter-seasonal levels

Note: Global epidemiology and surveillance updates are periodically collected from data reported by National authorities or organizations responsible for reporting this data. For further information on specific influenza virus activity in the world and scientific literature for practitioners and other professionals in the field, please visit the links provided at the end of this document.


Countries in the temperate zone of the northern hemisphere

North America

Influenza activity in North America has seen a sharp increase since the beginning of December 2012 extending into 2013, which is earlier than expected. Some indicators of influenza activity are still elevated while others indicate that activity might have peaked.

Influenza-like illness (ILI) consultation rates which have been increasing since early December 2012 declined slightly in Canada during the first week in January. The ILI consultation rate decreased from 67.1/1000 patient visits at the time of the previous report, to 58.7 during the first week of January, with the highest rates observed in children of the 5-19 age group, followed by the <5 years. The percentage of samples that tested positive for influenza also decreased slightly from 34.5% in the end of December to 32.4% in the beginning of January. But an increasing number of regions (two in AB, two in BC, one in MB, three in NL, five in ON, and two in QC) reported widespread influenza activity and the number of reported influenza outbreaks sharply increased in the first week of 2013. In the first week of January, 107 new influenza outbreaks were reported across the country, a markedly higher weekly number than any week of the previous two years. ILI consultations rates have also exceeded the 95% confidence intervals for two consecutive weeks in late December 2012. Of the 69 new laboratory confirmed influenza-associated paediatric hospitalizations, 55% were aged 0-2. In the first week of 2013, 298 laboratory confirmed influenza associated hospitalizations were reported, of which type and subtype information was available for 252. For these cases, 96.4% (243/252) were influenza A, of which, approximately 51.4% (125/243) were due to influenza A(H3N2) virus and 12.1% (5/243) were influenza A(H1N1)pdm09 virus. Just over half of these cases, 54%, (162/298) were aged 65+. Of the 138 cases with available data, 14.5% were admitted to the intensive care unit (ICU). Fourteen deaths were reported in week 1 of January, all but one were above 65 years old. The one exception was in a case aged 0-4 years with influenza A.

Influenza A continued to dominate in Canada, with few detections of influenza B. Of the 3,864 samples that were positive for influenza in the first week of January, 98.1% were positive for influenza A and 1.9% for influenza B viruses. Of the influenza A viruses that were sub-typed, 95.9% was A(H3N2) and 4.1% was A(H1N1)pdm09. Since the start of the season, the National Microbiology Laboratory (NML) has antigenically characterized 193 influenza viruses (143 A(H3N2), 25 A(H1N1)pdm09 , and 25 influenza B). The 143 influenza A(H3N2) viruses were antigenically similar to the vaccine virus A/Victoria/361/2011. The 25 A(H1N1)pdm09 viruses were antigenically similar to the vaccine virus A/California/07/09. Among the influenza B viruses, 21 were antigenically similar to the vaccine virus B/Wisconsin/01/2010 (Yamagata lineage) and four were similar to B/Brisbane/60/2008 (Victoria lineage; component of the 2011-2012 seasonal influenza vaccine). None of the viral samples tested against neuraminidase inhibitors oseltamivir (n=178) or zanamivir (n=176) were resistant.

Influenza activity in the US remained high, although there is some evidence that it might have peaked in some areas at the end of December. ILI consultation rates decreased to 4.3% which is still above the national baseline of 2.2%, with 32.8% of samples testing positive for influenza, down from 35.2 in the last week of December and the 3rd consecutive week of decline. Almost all states (47) reported widespread influenza activity. The proportion of all deaths attributed to pneumonia and influenza (P&I) reported through the 122 Cities Mortality Reporting System slightly exceeded the national threshold of 7.2% (the upper 90% confidence interval for the previous 10 seasons) for the first time in recent weeks but has generally been mid-range for most of the season. Two influenza-associated pediatric deaths were reported the last week of December, bringing the total for the season so far to 20 (34 pediatric deaths were reported during the 2011-12 influenza season). Both deaths were associated with influenza A, one of which was sub-typed as A(H3N2) virus. Between 1 October 2012 and 5 January 2013, 3 710 laboratory-confirmed influenza-associated hospitalizations were reported, a rate of 13.3 per 100 000 population. In comparison, the end of season cumulative rate of hospitalization in 2011-12 season, a relatively mild season, was 8.6 and 21.4 in 2010-11. The highest rates of hospitalization (53.4 per 100 000) were reported in individuals over 65 years of age followed by the 0-4 years (22.4 per 100 000). Among all hospitalizations, 86.2% (3198/3710) were associated with influenza A and 13.0% (484/3170) with influenza B virus. Among hospitalizations with influenza A subtype information, 98.7% (767/777) were attributed to A(H3N2) and 1.3% (10/777) were attributed to A(H1N1)pdm09. As expected, the greatest proportion of laboratory confirmed influenza

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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 and Response System) 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.

Link to web pages Epidemiological Influenza updates: http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance Epidemiological Influenza updates archives 2012: http://www.who.int/influenza/surveillance_monitoring/updates/GIP_surveillance_2012_archives Virological surveillance updates : http://www.who.int/influenza/gisrs_laboratory/updates/summaryreport Virological surveillance updates archives :

http://www.who.int/influenza/gisrs_laboratory/updates/en/index.html

Contact [email protected]

Documents

Update 177 final - WHO · Influenza Update N° 177 ... zed children zed children S, the major B accounte sitive for influ B. Of the in C ested were ested were A isconsin/1/ l influenza