Human influenza A/H3N2 activity increases in many countries in central and eastern Europe - update 8

21 January 2004

Summary of global influenza surveillance (to 10 January 2004)

Influenza activity associated with A/Fujian/411/2002-like viruses continued to increase and/or remained widespread in many central and eastern European countries (Austria, Croatia, Latvia, Norway, Russia Federation, Slovenia, Switzerland and Ukraine). Influenza activity also increased in Italy and Japan and remained widespread in some parts of Canada and USA.

Most reported influenza infections this season have been attributed to influenza A(H3N2) viruses. The majority of A(H3N2) viruses antigenically characterized so far have been shown to be A/Fujian/411/2002-like; the others have been A/Panama/2007/99-like.

In Viet Nam there have been 5 laboratory-confirmed cases of infection with A(H5N1) virus . All have died. On Tuesday 6 January, WHO announced influenza pandemic preparedness Phase 0 Level 2

Several countries have reported outbreaks of highly pathogenic influenza A(H5N1) in poultry. This is of great concern as frequent transmission of avian influenza viruses to humans increases the possibility for genetic reassortment with circulating human influenza strains and the possibility of a new influenza pandemic caused by such reassortant viruses. A WHO team has been sent to Viet Nam to investigate the outbreaks and WHO Collaborating Centres for Reference and Research on Influenza and some national reference laboratories are conducting antigenic and genetic analysis of the H5N1 viruses isolated from human and birds during the recent outbreaks in Asia. Results will guide WHO in preparing prototype viruses for pandemic vaccine production and providing diagnostic test kits for H5N1 viruses to national influenza centres.

Reports from individual countries

Austria. An increase in influenza activity was observed in week 2 (4–10 January), although the acute respiratory illness (ARI) consultation rate was still below the epidemic threshold.

Belgium. Influenza A(H3N2) activity continued to decline in week 2, with a fall in both the number of viruses identified and the influenza-like illness (ILI) consultation rate. Regional influenza activity was reported for week 2.

Canada. In week 2, widespread influenza activity continued in Newfoundland, Quebec and Ontario. The overall ILI consultation rate was 40 cases per 1000 consultations, which was within the expected range for the time of year. Of the 490 influenza viruses antigenically characterized by the National Microbiology Laboratory to date, 456 (93%) were A/Fujian/411/2002-like, 25 (5%) were A/Panama/2007/99-like, one was an A/New Caledonia/20/99 (H1N1)-like virus, one was A(H1N2) and 7 (1.4%) were influenza B viruses (1 B/Hong Kong/330/2001-like and 6 B/Sichuan/379/99-like).

Croatia. Influenza A(H3N2) activity continued to increase significantly and was reported as widespread for week 2, with 10 influenza A(H3N2) and 11 A non-subtyped viruses identified.

Denmark. Influenza activity declined in week 2, with the ILI consultation rate dropping below the epidemic threshold.

France. Influenza activity continued to decline throughout France. Widespread influenza A(H3N2) activity was reported in one region for week 2.

Germany. Localized influenza activity was reported for week 2, with 9 influenza A(H3N2) and 9 A non-subtyped viruses identified.

Israel. Influenza activity remained at a low level in week 2, with 7 influenza viruses detected.

Italy. Influenza activity was reported as sporadic, with a slight increase in influenza A(H3N2) activity in week 2.

Japan. Influenza activity increased in week 2, with 37 influenza A(H3N2) viruses detected (compared with 6 in week 1).

Latvia. Influenza A(H3N2) activity increased significantly in week 2, with localized activity reported.

Norway. Influenza activity has been declining gradually since week 51, although significant activity still remained in large parts of the country in week 2. Of 919 influenza A virus detected so far this season, 237 were subtyped as A(H3) and 27 as A(H1). All A(H3) strains antigenically characterized were A/Fujian/411/2002-like and all A(H1) strains were A/New Caledonia/20/99-like. The neuraminidase of recent A(H1N2) viruses was N2.

Romania. Regional influenza activity was reported for week 2, with medium ARI morbidity.

Russia Federation. Widespread influenza activity persisted. In 21 of 34 cities, ILI morbidity exceeded the epidemic threshold by 16.6–127.8% in week 2.

Slovenia. Influenza activity increased significantly in week 2 and was reported as regional.

Sweden. The ILI consultation rate decreased in week 2, with 138 influenza viruses detected. Influenza activity was reported as regional.

Switzerland. In week 2, the ILI consultation rate and the number of influenza viruses detected declined for the first time since the beginning of the recent epidemic phase, although activity remained widespread. All strains antigenically characterized were closely related to influenza A/Fujian/411/2002-like virus.

Ukraine. In week 2, widespread influenza activity was reported in the north and east the country; an increase in activity was observed in the west.

United Kingdom. During week 2 the ILI consultation rate changed little in England, Scotland and Wales but increased slightly in Northern Ireland. The number of specimens decreased following the overall decline in influenza activity. No influenza virus was detected during week 2. Of the viruses antigenically characterized, 172 (97%) have been confirmed as A/Fujian/411/2002-like, 3 as A/Panama/2007/99-like and 2 as B/Hong Kong/330/2001-like.

United States. The overall ILI consultation rate, the number of states reporting widespread influenza activity and the percentage of specimens testing positive for influenza continued to decrease in week 2. However, pneumonia and influenza mortality (10.2%) continued to increase and exceeded the epidemic threshold (8.1%) for the time of year. Widespread influenza activity was reported in 20 states and in New York City, and regional activity was reported in 24 states during week 2. Of the specimens tested, 11.9% were positive for influenza, with 313 influenza A viruses and 6 B viruses identified. Since week 40, the Centers for Disease Control and Prevention in Atlanta have antigenically characterized 2 influenza A(H1) viruses, 511 A(H3N2) viruses and 5 B viruses from the USA. Of the 511 A(H3N2) viruses characterized, 98 (19.2%) were A/Panama/2007/99-like and 413 (80.8%) were A/Fujian/411/2002-like.

Other reports. Low influenza activity was reported in Greece, Guyana, Hong Kong Special Administrative Region of China, Hungary, Morocco and Portugal. Argentina, Australia, Madagascar, Poland and Spain reported no influenza activity.