Emerging disease surveillance and response

Influenza Situation Update

15 April 2014

Summary

In the Northern Hemisphere countries, influenza-like illness (ILI) activity has decreased. In northern China, during the week 31 March to 6 April 2014, the percentage of visits for ILI (ILI%) at national sentinel hospitals established in 2009 in north China was 2.8%, which was lower than the previous week and the same week in 2013 (both 2.9%). The proportion of ILI specimens positive for influenza has also decreased: 116 of 976 (11.9%) ILI specimens were positive for influenza. Of the positive specimens, 18 (15.5%) were influenza A (13 were H3N2 and 5 were (H1N1)pdm09) and 98 (84.5%) were influenza B(4 Yamagata and 94 lineage not determined). In Mongolia, during the week 24 to 30 March 2014, ILI activity based on the proportion of outpatients exhibiting ILI substantially decreased compared to 2 weeks ago and was just below the upper tolerance limit (60%). The proportion of patients with pneumonia among the hospitalized was also lower compared to 2 weeks ago. The proportion of ILI specimens positive for influenza also decreased; there were 40 specimens positive for influenza virus among 132 ILI samples (30.3%) submitted: of those laboratory confirmed, 8 were influenza A(H3) and 32 influenza B (lineage not determined) during 23 to 29 March 2014. In Japan, during the week 3 to 9 April 2014, ILI activity decreased; the number of ILI cases per sentinel reporting site was 6.1, lower than the previous week. Similarly, in the Republic of Korea, for the week ending 5 April 2014, ILI activity continued to decrease; the number of ILI cases was 15.3 per 1000 patients at sentinel sites, lower than the previous week. Proportion of ILI specimens positive for influenza also decreased; there were 111 specimens positive for influenza virus among 239 (46.4%) ILI samples submitted: 21 influenza A(H3), 5 influenza A(H1N1)pdm09 and 85 influenza B (lineage not determined) during 23 to 29 March 2014.

In the subtropics/tropics, overall ILI activity remained variable. In Southern China, during the week 31 March to 6 April 2014, the ILI at national sentinel hospitals established in 2009 in south China was 3.2%, which was higher than that of the previous week (3.1%) higher than that for the same week of 2013 (3.0%). However, the proportion of ILI specimens positive for influenza has decreased: 273 of 2663 (10.3%) ILI specimens were positive for influenza. Of the positive specimens, 95(34.8%) were influenza A (28 were H3N2, 60 were (H1N1)pdm09 and 7 subtype not determined) and 178 (65.2%) were influenza B(lineage not determined). In Hong Kong (China), during 30 March to 5 April 2014, local influenza activity has continued to decrease but not returned to baseline level yet. Of the 276 samples positive for influenza during this week, 40 were influenza A(H3), 46 were influenza A(H1N1)pdm09, 184 were influenza B and 6 were influenza C viruses. During 30 March to 5 April 2014, hospital admission rates with principal diagnosis of influenza decreased for children aged 0–4 years, persons aged 5–64 years and persons aged 65 years and above (0.81, 0.06 and 0.34 cases per 10 000 people in the age group, respectively). Additionally, weekly number of deaths with any diagnosis of influenza in public hospitals has decreased.

In the Mekong, influenza activity was variable. In Lao PDR, during 16 to 22 March 2014, 6 of 50 (12.0%) ILI specimens were positive for influenza: 3 were influenza A(H1N1)pdm09and 3 were influenza B (Lineage not determined). In Viet Nam, the influenza activity slightly increased. During 30 March to 5 April 2014, 12 of 34 (35.3%) ILI specimens were positive for influenza: 3 were influenza A(H1N1)pdm09, 3 was influenza A(H3) and 6 were influenza B (Lineage not determined).

In Singapore, acute respiratory infection (ARI*) activity decreased. During 30 March to 5 April 2014, 2,059 patients sought treatment compared to 2,198 patients the previous week. The proportion of cases with ILI among the polyclinic ARI cases remained low at below 1%. Of 100 ILI samples collected in the past 4 weeks in the community, 33.0% were positive for influenza virus. Of all the influenza virus isolates in March 2014, 8.8% were influenza A(H3N2), 23.5% were influenza A(H1N1)pdm09 and 67.6% were influenza B.

In Australia, ILI activity increased compared to the previous two weeks, but remained at low level. During the week 23 to 29 Mar 2014, 16 of 227 (7.0%) ILI specimens tested positive for influenza: 8 was influenza A(H3), 6 were influenza A(H1) and 2 were influenza B (lineage not determined).

In the Pacific Islands, ILI activity was variable with an increase observed in a number of islands. During the week ending 6 April 2014, Fiji, New Caledonia and Palau reported weekly ILI case numbers above the threshold of 90% of their historical values.


Global influenza situation

Epidemiological update:
http://www.who.int/influenza/surveillance_monitoring/updates/latest_update_GIP_surveillance/

Virological update:
http://www.who.int/influenza/gisrs_laboratory/updates/summaryreport


*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.


For further information on the influenza situation or its surveillance, please visit the following links:


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