Influenza Situation Update
7 May 2013
Human infection with avian influenza A(H7N9) virus in China
As of 07 May 2013, total number of confirmed human cases in mainland China is 129, with 31 deaths, 42 recovered. 1 case has also been reported by Taipei Centers for Disease Control. There is no evidence of sustained person to person transmission. The source and mode of transmission remain unknown, but increasing evidence pointing to poultry exposure.
The Chinese government is responding to the event with enhanced surveillance, investigations, close contact tracing, laboratory testing, clinical management, culling of poultry and closing of markets. The WHO-coordinated international response is also focusing on work with WHO Collaborating Centers and partners to ensure that information is available and that materials are developed for diagnosis and treatment and vaccine development. 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 reassess the situation as it evolves. As more information becomes available WHO will revise its guidance and actions accordingly. For more information, visit:
In the Northern Hemispherecountries, there has been varied influenza-like illness (ILI) activity, with circulation of influenza A (H1N1) pdm09, A (H3) and influenza B. In northern China, during the week 15 to 21 April 2013, the percentage of visit for ILI (ILI%) at national sentinel hospitals established in 2009 in north China was 2.4%, which was slightly higher than that of the previous week (2.1%) and the same period of the previous year (2.2%). 44 of 1114 ILI specimens were positive for influenza (3.9%): 33 were influenza A (H1N1)pdm09 and 11 were influenza B (lineage not determined).In Mongolia, during 22 to 28 April, ILI activity based on the proportion of outpatients that were ILI has shown a decreased 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 15 to 21 April, ILI activity increased slightly in Japan but remained low; the number of ILI cases per sentinel reporting site was 2.9 relative to 2.0 the previous week. Of 5 influenza viral isolates tested positive during the same week, 2 were influenza H3N2, 3 were influenza B (Yamagata lineage). In the Republic of Korea, for the week ending 27 April 2013, influenza activity continued to decrease, and the number of ILI cases was 3.6 per 1000 patients, lower compared to the previous week (4.1 per 1000). 33 of 314 (10.5%) ILI specimens were positive for influenza virus during this week: 24 influenza A (19 A(H3) and 5 A(H1N1)pdm09) and 9 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 15 to 21 April 2013, the ILI% at national sentinel hospitals established in 2009 in south China was 3.5%, which was slightly higher than that of the previous week (3.3%) and also higher than the level seen during the same period of the previous year (2.5%). 231 of 2287 ILI specimens were positive for influenza (10.1%): 219 were influenza A (181 H1N1pdm09, 37 H3N2, 1 subtype not determined) and 12 were influenza B (lineage not determined). In Hong Kong (China), local influenza activity has remained low during 21 to 27 April. Of the 159 samples positive for influenza during this week: 125 influenza A (H1N1)pdm09, 26 influenza A (H3) and 8 influenza B. In the Mekong, low level influenza activity was reported. In Cambodia, during 7 to 13 April, 23 samples received and none were positive for influenza. In Lao PDR, during 14 to 20 April, 1 ILI sample received but not positive for influenza. In Viet Nam, during 21 to 27 April 2013, 31 ILI samples received and 4 were positive for influenza: 1 was influenza A(H3N2), 3 were influenza B (lineage not determined). In Singapore, acute respiratory infection (ARI*) activity remained stable at 2 699 during 21 to 27 April 2013, compared to 3 022 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 134 ILI samples collected in the past 4 weeks, 23.9% were positive for influenza virus. Of all the influenza virus isolates on March 2013, 45.8% A/H1N1pdm09, 29.2% A/H3N2, and 25.0% influenza B.
In the Southern Hemisphere ILI activity remained low. During 21 to 27 April 2013 in Australia, 1 out of 225 ILI samples received was positive for influenza A (H1N1) pdm09. In New Zealand, influenza activity continued to remain low and below the baseline threshold.
In the Pacific Islands, ILI activity was mostly low and stable. During the week ending 28 April 2013, American Samoa, Tuvalu and Wallis & Futuna 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.