H7N2 Avian Influenza Outbreak in Conway: Case Investigation and Response

1. One flu over the chickens house – the tale of H7N2 and a wide cohort of people Dr Marion Lyons

2. Background • Since 1998 there have been the following human cases of avian influenza infection with viruses other than H5N1: 1. H9N2: China 1998 - 6 cases; Hong Kong 1999 - 2 cases; Hong Kong 2003 - 1 case; Hong Kong 2007 - 1 case 2. H7N2: USA 2002-3 - 2 cases 3. H7N7: Netherlands - 89 cases (1 death) 4. H7N3: Canada 2004 - 2 cases; UK 2006 - 1 case 5. H10N7: Egypt - 2 cases.

3. Rationale for action The rationale for the substantial response mounted by the NPHS and wider NHS to this incident was: • the protection of the health of both individuals and the wider population. • The rapid detection of human cases allows early treatment with antiviral medication to reduce morbidity and mortality in these individuals. • From a public health or population perspective the rationale for the response is to rapidly utilise all feasible opportunities to prevent the avian virus from developing the ability to start an influenza pandemic.

4. The Incident • NPHS informed on the afternoon of the 23rd May of the finding of H7 Influenza A in dead chickens on a small holding in Conway • The owner had bought 15 young Rhode Island Red chickens from a market in Chelford, Cheshire, on May 7th. He added them to his existing flock of chickens • By 17th May, about ten of the new chickens had died • He called his private vet, who came and took some of the chickens to his surgery and sent samples for microbiological testing. These were confirmed as showing H7 influenza virus (the N type was not yet available) on 23rd May • By this time, fifteen birds had died and Animal Health (previously the State Veterinary Service) decided to cull the remaining 30 hens and two geese

5. What to do?A “Strict approach” “The principles of the Strict approach include: • Keeping the numbers of persons exposed to an absolute minimum • Commencing prophylaxis with Neuraminidase inhibitors for persons already exposed (who have been in close contact with infected birds) as soon as possible • Advising persons who are likely to be exposed as responders to commence prophylaxis in advance of commencement of duties and ascertaining satisfaction with Personal Protective Equipment (PPE) use • Follow-up of exposed persons and/or their close or family contacts dependent on expert epidemiological and virological advice

6. Who was at risk? • The two people on the smallholding in North Wales were interviewed by phone to establish their symptoms, their date of onset and the details of their contact with the confirmed infected poultry. • Both of these fitted the criteria for human cases and therefore the details of any human contacts these two people had had during their period of possible infectivity was established. • It became clear that a family living nearby had visited the smallholding and also had had significant contact with the owner when he visited them, whilst he was symptomatic, at their own home. (Two of the members of this family had developed symptoms and fitted the case criteria)

7. Dealers Purchasers 7 May 2007 Corwen Animal illness Chickens, Ducks, Peacocks 15 Laying hens Leicester No animal illness 13 cases 139 contacts Chelford Market, Cheshire 11 Ducklings St Helens 1 Unconfirmed animal illness Lleyn Peninsular No animal illness, 1 case 77 contacts Ducklings 20 chickens, 3 ducks, 3 peacocks 4 cases 91 contacts St Helens 2 Animal illness 2 cases 7 contacts Wales was not alone Figure 1: Connection between poultry movements and human infection

8. Management of the incident At the first NPHS meeting, the tasks needing to be done immediately were identified: • to determine the full details of human contacts of the infected poultry • to communicate with local GPs, microbiologists, Local Health Board Chief Executives and all CCDCs, and to inform LA s. • to contact Animal Health vets and staff to arrange for their anti viral prophylaxis prior to culling • to contact local Accident and Emergency Departments and inform them of signs and symptoms to be aware of

9. Case ascertainment • Any person who was identified as fitting the criteria for a case was assessed by a doctor, mostly on a home visit. • A clinical assessment was made according to the definitions. If the assessment fitted the case definition, samples were taken for investigation and advice given to the person. Oseltamivir at a treatment dose was prescribed by the GP undertaking the assessment.

10. Definition of a case • The following case definitions were used: • Definite case: Individual with laboratory confirmed diagnosis of influenza • Suspected case: Individual in close contact with infected flock or definite or treated case if with influenza-like illness (respiratory tract symptoms, fever, myalgia) or conjunctivitis • The definition used by GPs in their clinical assessments from 24th May was Clinical Presentation: • Fever (≥ 38°C) OR history of fever AND respiratory symptoms (cough or shortness of breath), flu like illness including myalgia, OR conjunctivitis AND Epidemiological criteria: • Close contact (within 1 metre in a closed environment) with live or dead affected chickens from the affected farm in Corwen, North Wales, OR sick birds with confirmed or suspected Avian flu within 8 days prior to onset of symptoms. • OR • Close contact (household contact) with a symptomatic human case.

11. Contacts of cases Primary - Individual in contact with an infected flock Secondary - Individual not in contact with an infected flock who is in contact with a case (definite or suspected) Close contact with infected poultry was defined on 23rd May as: • Close contact with birds and/or litter (within 1 metre) in an “indoor environment” such as laying sheds. • Close contact with a human case was defined on 25th May as: • Anyone who had been in close contact for several hours with a human case in the period 24 hours prior to onset of symptoms until 8 days after onset.

12. Epidemiology results By the end of the incident, 14 probable cases and 216 contacts had been identified using the clinical and epidemiological criteria established on Day 1. The sequence of daily changes to the database is shown in Table 3.

13. Attack rate by proximity of contact to infected poultry

14. Cases and contacts by site

15. Control measures • PPE • Prophylaxis and treatment doses of oseltamivir • 84 people given prophylaxis • 16 people given treatment doses • oseltamivir contraindicated in 1 person

16. Partnership working • WAG • LHBs and primary care organisations • HPA • North Wales Police • DEFRA

17. Communications 1. Cases, contacts and their families • Direct contact with cases, contacts and their families • Letters (schools, cases reminding them to have follow up blood samples etc) • Meetings (2 meetings arranged at the school) 2. Public • Help lines, Website, Leaflets and Media

18. Communications cont. 3. Communication with partner organisations • HPA • LHBs • LA 4. Health Professionals • Daily teleconference • Daily liaison with key workers • Written guidance for all GPs, A&E Departments and pharmacists 5. Hospitals • Via Consultant Micribiologists 6. Public Officials and elected members

19. Conclusions • There was an outbreak of H7N2 avian influenza in poultry in England and Wales, affecting birds at three premises in Denbighshire, Merseyside and Nottinghamshire in May and June of 2007 • There was an epidemiological link between the sites through the live poultry market that took place at Chelford in Cheshire on May 7th 2007 • Virologically confirmed influenza A, believed to be of the same type as that isolated from the poultry, occurred in four persons, two of whom lived in Wales with the other two living in North West England.

20. Conclusions • Thus, transmission of H7N2 to human beings occurred. • The occurrence of influenza like illnesses among persons, 11 in Wales, who either had no, or minimal, contact with infected birds also meant that transmission of H7N2 from person to person may have occurred • The public health management, as a precaution, however, actively addressed the possibility of person to person spread by identifying contacts and arranging for them to receive oseltamivir. • Thus, during the public health response in Wales, 14 people were treated as probable cases of avian influenza and 218 people were treated as contacts.