Influenza Situation Update
21 May 2013
Summary
Human infection with avian influenza A(H7N9) virus in China
As of 21 May 2013, a total of 131 cases have been reported (130 from China's National Health and Family Planning Commission and 1 from Taipei Centers for Disease Control). Of these patients, 36 have died. No new cases reported since 8 May 2013 and normalization of emergency operations into routine surveillance and response activities has begun. So far, there has been no evidence of sustained human-to-human transmission. The source and mode of transmission remain unknown, but increasing evidence pointing to poultry exposure. Until the source of infection has been identified and controlled, it is expected that there will be further cases of human infection with the virus.
WHO does not advise special screening at points of entry with regard to this event, nor does it recommend any travel restrictions be applied. WHO continues to work closely with national authorities and technical partners to gain a better understanding of this disease in humans and will continue to provide updated information. WHO will continue to assess the situation and as more information becomes available WHO will revise its guidance and actions accordingly. For more information, visit:
http://www.wpro.who.int/outbreaks_emergencies/H7N9/en/index.html
http://www.who.int/influenza/human_animal_interface/faq_H7N9/en/index.html
In the Northern Hemispherecountries, there has been declining influenza-like illness (ILI) activity, with circulation of influenza A (H1N1) pdm09, A (H3) and influenza B. In northern China, during the week 6 to 12 May 2013, the percentage of visit for ILI (ILI%) at national sentinel hospitals established in 2009 in north China was 2.1%, which was lower than that of the previous week (2.4%) and was also lower compared to the same week of 2012 (2.2%). 6 of 998 (0.6%) ILI specimens were positive for influenza: 5 were influenza A (H1N1)pdm09 and 1 was influenza B (lineage not determined). In Mongolia, during 6 to12 May 2013, ILI activity based on the proportion of outpatients that were ILI continued to show a decreasing trend. During the week 1 to 7 April, among 120 ILI samples, 3 were positive for influenza, all influenza A (H1N1) pdm09. During the week 29 April to 5 May 2013, ILI activity remained low and slightly decreased in Japan; the number of ILI cases per sentinel reporting site was 2.36 relative to 3.07 the previous week. Of the 2 influenza viral isolates that tested positive during the same week, 1 was influenza A(H3) and 1 was influenza B (lineage not determined). In the Republic of Korea, for the week ending 11 May 2013, ILI activity continued to decrease, and the number of ILI cases was 2.9 per 1000 patients, similar to the previous week (2.8 per 1000 patients). 22 of 272 ILI specimens were positive for influenza virus: 11 influenza A (7 A(H3) and 4 A(H1N1)pdm09) and 11 influenza B (lineage not determined).
In the subtropics/tropics, ILI activity was stable and low, with circulation of A (H1N1)pdm09, influenza A(H3), and influenza B. In Southern China, during the week 6 to 12 May 2013, the ILI% at national sentinel hospitals established in 2009 in south China was 3.1%, which was lower than that of the previous week (3.3%) but higher than the level seen during the same period of the previous year (2.7%). 182 of 2305 (7.9%) ILI specimens were positive for influenza: 178 were influenza A (158 H1N1pdm09, 13 H3N2, 7 subtype not determined) and 4 were influenza B (lineage not determined). In Hong Kong (China), local influenza activity continued to decline during 5 to 11 May 2013. Of the 106 samples positive for influenza during this week: 77 influenza A(H1N1)2009, 23 influenza A (H3) and 6 influenza B. In the Mekong, low level influenza activity was reported. In Cambodia, during 14 to 20 April 2013, 39 samples received and none were positive for influenza. In Lao PDR, during 21 to 27 April, 33 ILI sample were received and 2 were positive for influenza B(lineage not determined). In Viet Nam, during 14 to 20 April 2013, 54 samples received and 14 were positive for influenza: 12 were influenza A(H1N1)pdmo9, 1 was influenza (H3), 1 was influenza (H5). In Singapore, acute respiratory infection (ARI*) activity remained stable at 2747 during 5 to 11 May 2013, compared to 2854 in the previous week, remaining below the warning level. The proportion of cases with ILI among the polyclinic ARI cases remained low at 1%. Of 162 ILI samples collected in the past 4 weeks, 18.5% were positive for influenza virus. Of all the influenza virus isolates on April 2013, 44.7% influenza A(H3N2), 31.6% influenza A(H1N1-2009), and 23.7% influenza B.
In the Southern Hemisphere ILI activity remained low. During 5 to 11 May 2013 in Australia, of 208 ILI samples received, 1 was positive for influenza A (H1N1) pdm09 and 1 influenza B(lineage not determined). In New Zealand, during 5-12 May 2013, influenza activity continued to remain low and below the baseline threshold. 7 out of 149 samples received were positive for influenza: 3 B(not typed), 2 A(H3N2), 1 A/Perth/16/2009(H3N2), and 1 A(not sub-typed).
In the Pacific Islands, ILI activity was mostly low and stable. During the week ending 12 May 2013, only American Samoa reported weekly ILI case numbers above the threshold of 90% of its historical values.
*ARI defined as clinical diagnosis of acute upper respiratory tract infection (ICD9 460 – 465: Acute Nosopharyngitis (common cold); 461 Acute Sinusitis; 462 Acute Pharyngitis; 463 Acute Tonsillitis; 464 Acute Laryngitis and Tracheitis; 465 Acute Upper Respiratory Infections of Multiple or Unspecified Sites; 466 Acute Bronchitis and Bronchiolitis). ILI defined as temperature >38C with cough or sore throat.