Descriptive Epidemiology of HPAI H5N1 in the Baltic Sea Region in 2006

1. Descriptive Epidemiology of HPAI H5N1 in the Baltic Sea Region in 2006 Preben Willeberg DVM, PhD, Dr. Vet. Sc., Dr. Vet. Sc.h.c., Dipl. ECVPH CVO, Professor

2. World-wide occurrence of HPAI H5N1

4. AI-infected tufted duck

5. Chronology of HPAI H5N1- events in or near Denmark in 2006 • 15 February – wild bird case in Rügen • Early March – w.b.cases in Sweden • 12 March – first w.b.case in Denmark • 2 May – 43rd w.b. case in Denmark • 18 May – positive back-yard poultry flock • 24 May – positive magpie on AI premise

6. Week 7

7. Week 8

8. Week 9

9. Week 10

10. Week 11

11. Week 12

12. Week 13

13. Week 14

14. Week 15

15. Week 16

16. Week 17

17. Week 18 - 19

18. Week 20 - 21

19. Week 22+

20. Monthly distribution of HP H5N1 cases in wild birds 2006

21. Predicted risk areas (March 2006) poultry density & wild water fowl locations

22. Location of wild birds tested for HPAI January through May 2006

23. Diagnostic methods Routine test: RT-PCR for influenza A and specific H5 subtype RT-PCR: specific H7 subtype Pos influenza A – negative H5 Sequencing of PCR-product – HP or LP Positive subtype H5 Positive subtype H7 Pos influenza A - negative H7 Pos influenza A - negative H5 RT-PCR for nucleoprotein Influenza A confirmation + Inoculation in embryonated eggs

24. Table 1 Location of cases of HPAI H5N1 in wild birds in 2006 County Number of AI pos. No. of birds tested Prop. mortality rates Nordjylland 0 74 - Viborg 0 21 - Århus 0 52 - Ringkøbing 0 25 - Vejle 0 46 - Ribe 0 47 - Storstrøm 8 93 9% Fyn 27 141 19% Frederiksborg 4 58 7% Sønderjylland 3 170 2% Vestsjælland 1 67 2% Roskilde 0 21 - Københavns/Frb. kommune 0 57 - Bornholm 1 97 1% Unknown 0 151 - Total 44 1120 (626) 4% (7%) Location by county of AI tested dead wild birds in 2006

25. Number of dead wild birds tested January through June 2006

27. The affected zones (April) and bird species

28. Zones established as of 7 April 2006 Red: Protection zones Blue: Surveillance zones

29. Additional testing • 1112 samples of bird dropping have been analysed by PCR • These samples were collected ultimo February to ultimo April 2006. • All samples have given negative test results, except one pool with samples from five herring gulls (Larus argentatus), which were HP H5N1-pos.

30. The first outbreak of HPAI H5N1 in Denmark • Confirmed: 18 May 2006 • Location: Near the town of Kerteminde on the island of Funen. • Affected population: A backyard poultry holding with 102 animals (51 chickens, 41 ducks, 5 geese, 3 guinea fowls and 2 peacocks) of which 47 had died. • Source of infection: Contact with wild birds.

31. Mortalityreported by owner

32. Zones and areas 18 May 2006

33. Species North Germany Sweden Number of cases Proportion Number of cases Number of tested birds Proportional mortality rate 138 6 58 Swans 10% 3 74 4% 48 230 21% 35 0 85 - 9 1 60 Crows 2 0 21 Total 222 58 528 Occurrence of HPAI in Northern Germany and Sweden by species 10% 62% Birds of prey 23 Ducks 15 7% Other water fowl - 16% 2% Gulls and terns 4% - 1% 11% 100%

34. Proportional mortality by species

35. Wild birds tested in other member states around the Baltic Sea (February – May 2006) H5N1-positive H5N1-negative Estonia 0 151 Finland 0 440 Latvia 0 139 Lithuania 0 574 Poland 70 (3.5%)* 1904 * 67 were swans

36. AI ”frontier” in Europe

37. Discussion • Why did it last 4 weeks for the infection to reach the 40 km from Rügen to the Danish coast? • AI “frontier” through Europe/Denmark – did the infection stop /die out – or did the birds just fly somewhere else – and what about the indigenous birds? • First cases of documented spread from poultry to wild birds and of “healthy carriers” in Europe? • Species differences among wild birds in risk of transmission – which birds to monitor?

38. Possibilities of a “die-out” of the (local) epidemic ? • Low AI-specific mortality, which was only detected due to (unusually?) high unspecific mortality (cold winter) – so AI epidemic was never severe (after Rügen) • Possible reasons for low AI-specific mortality: • Low field diagnostic sensitivity – with PCR not likely? • Low case fatality – not likely with HPAI H5N1 – species differences? • Low incidence of AI infection in regional wild birds – species differences? Reason for few situations of poultry becoming affected? • Low prevalence of AI infections – self-cure? Immunity? Species differences? • Lower no. of cases and % HPAI of dead birds by month and sub-region – migration of birds would presumably not change % of HPAI among dead birds (unless all infected birds migrated) • “Frontier” without other sub-regions on the migration route becoming affected (Norway, Finland) • Could a “die-out” in late spring explain the absence of infection in the fall migration (so far)? • What are the reasons for a “die-out”?

39. Decision to raise risk level from low to medium ---------------------------------------------------------------------------------------  Cases --------------------------- ---------------------------------------------------------- No. tested All neg. < X YES YES Surveillance of relevant wild ---------------------------------------------------------- bird populations during the > X NO YES relevant period  --------------------------------------------------------------------------------------------- X: for design prevalence = 5% with 95% confidence: X = 60 for design prevalence = 5% with 99% confidence: X = 90 for design prevalence = 1% with 95% confidence: X = 300 for design prevalence = 1% with 99% confidence: X = 460

40. Questions or comments?