Last updated:
12 December 2005
1. Reason for surveillance
- To rapidly identify, isolate, and treat cases.
- To rapidly identify contacts of cases and of infected birds so that they can be counselled, assessed, placed under surveillance, offered chemoprophylaxis with antiviral agents, and rapidly isolated should symptoms occur.
- To describe the epidemiology of avian influenza (AI) in humans in NSW.
2. Case definition
Suspected Case
A suspected case requires clinical evidence and epidemiological evidence. Clinical evidence
Person with acute respiratory illness, characterized by fever (temperature >380C), cough, and fatigue. Epidemiological evidence
Onset of symptoms within seven days of:
- contact with a confirmed human case of AI during the infectious period (i.e., one day before to 7 days after onset of AI illness (for children aged 12 years or less - one day before and 21 days after onset of illness)
OR
- close contact with poultry, or with any dead birds where the cause of death is unknown, in an area known to have outbreaks of AI
OR
- working in a laboratory that processed samples from persons or animals suspected of having AI infection.
Confirmed Case:
A confirmed case requires clinical evidence and laboratory definitive evidence. Laboratory definitive evidence
One or more of the following positive laboratory tests:
- Isolation of AI virus by culture from appropriate respiratory tract specimen, or
- Detection of AI virus by nucleic acid testing from appropriate respiratory tract specimen, or
- Detection of AI virus antigen from appropriate respiratory tract specimen, or
- Immunofluorescence antibody (IFA) test positive using specific AI antiserum, or
- Single high titre antibody to AI virus or a fourfold or greater rise in titre to AI virus.
Factors to be considered in case identification
In the unusual event that an AI strain transforms into one that is easily transmitted between humans, it is no longer avian influenza, but becomes human (and possibly pandemic) influenza. The response to human pandemic influenza is described in the national and state influenza pandemic management plans. The evidence base for defining what constitutes "contact" with a human case is limited. For the purposes of the case definition, it is taken to mean being within one metre of an infectious case for any length of time, or the same room as an infectious case for at least one hour. An AI-affected area is defined as a region within a country with confirmed outbreaks of AI strains as reported by the World Organization for Animal Health (OIE, http://www.oie.int/eng/en_index.htm). With respect to the H5N1 AI outbreak that commenced in Asia in 2003, information regarding A(H5)-affected countries is available at http://www.who.int/csr/disease/avian_influenza/country/en/ . The case definition is based on available clinical, epidemiological and laboratory data and it should be recognised that it may be modified as a better understanding of the disease in humans unfolds. Because of the current uncertainty about whether person-to-person transmission occurs, and the possibility that the AI strain could mutate in to a form that is more easily spread from person-to-person including via airborne spread, cases require airborne, droplet, contact and standard infection control precautions.
3. Notification criteria and procedure
Avian influenza in humans is notifiable by:
- medical practitioners and hospital CEOs
It is recognised that the heightened awareness about AI should prompt clinicians to report cases to their local PHU for help in the triage and management of suspected AI cases. PHUs should report suspected and confirmed cases to the Communicable Diseases Branch (CDB) by telephone immediately on notification. In the event of AI being identified in NSW birds, the NSW Department of Primary Industries (DPI) will notify NSW Health, which will notify the relevant Public Health Unit.
4. The disease
Infectious agent
Avian influenza virus. All AI viruses are influenza A viruses and multiple subtypes of influenza are known to infect birds. AI viruses can have low or high pathogenicity in poultry - LPAI or HPAI. To date, only H5 and H7 varieties have been known to cause outbreaks of HPAI in birds although both LPAI and HPAI can rarely cause illness in humans following very close contact. It is believed that human pandemic influenza strains may mutate from AI viruses. Mode of transmission
Infected birds shed virus in their saliva, nasal secretions, and faeces. Susceptible birds become infected when they have contact with contaminated excretions from infected birds or from contaminated surfaces or water. Transmission of infection from birds to humans is uncommon. When it has occurred, it is believed to have resulted from close contact with infected poultry or breathing in dust contaminated with their excretions. Although unequivocal evidence is lacking, it remains a possibility that a small number of human cases have occurred as a result of close and prolonged person-to-person transmission, the precise mode of which is unknown. The virus can survive on poultry products (including eggs and blood) but the risk of infection from these can be minimised by cooking the products, and regular hand-washing. Timeline
Although the incubation period for avian influenza may vary with the subtype, the typical incubation period for influenza is 1-4 days, with an average of 2 days. Adults can be infectious from the day before symptoms begin through to approximately 5 days after illness onset. Children can be infectious for > 10 days, and young children can shed virus for several days before their illness onset. Severely immunocompromised persons can shed virus for weeks or months. Clinical presentation
The clinical presentation of AI in humans may vary with the virus subtype. All subtypes can cause symptoms typical of human influenza (fever, cough, fatigue, myalgia, sore throat, shortness of breath, runny nose, headache). The most common presentation of humans infected with H7 strains is conjunctivitis. The H5N1 subtype has caused viral pneumonia with a high mortality rate, and in small number of cases, an encephalitic or diarrhoeal presentation has been reported.
5. Managing single notifications
Response time
Investigation
Immediately on notification of a suspected case, begin follow up investigation and notify the CDB. The form "Avian Influenza (AI) in humans - Reporting Form" (see appendices) should be completed and faxed to CDB the same day. Data entry
Within 1 working day of confirmation, enter confirmed case on NDD as Disease: influenza (avian); Organism: influenza virus; Subtype: (for example) H5N1. Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. Regardless of who does the follow-up, PHU staff should ensure that action has been taken to:
- confirm the onset date and symptoms of the illness
- confirm results of relevant pathology tests, or recommend that tests be done (the laboratory should be advised before sending the specimens)
- find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview
- seek the doctor's permission to contact the case or relevant care-giver
- review case and contact management
- ensure appropriate infection control professionals are notified and infection control policies are available to those caring for the case
- identify the likely source of infection.
Case management
Investigation
Obtain a travel history, and follow up clinical results and case details. See "Recommended samples for laboratory workup for suspected cases of avian influenza (AI)" (in appendices) for guidance on laboratory testing. Note. If interviews with suspected cases are conducted face-to-face, the person conducting the interview must have a thorough understanding of infection control practices, be competent in using appropriate personal protective equipment (PPE), and ideally have been vaccinated with the current (human) influenza vaccine. Treatment
The PHU must ensure that case management follows "Avian influenza (AI) in humans: Interim guidance for recognition, investigation and infection control" (in appendices). Antiviral medications have been shown to attenuate disease in cases of human influenza if given early in the course of the illness (within 48 hours). They may also be effective for treating AI. The preferred agents are neuraminidase inhibitors (oseltamivir and zanamivir). Education
Provide Avian Influenza Fact Sheet to cases and their close contacts. Ensure that they are aware of the signs and symptoms of AI, the requirements of isolation, contact details of the PHU and the infection control practices and precautions that can prevent the transmission of AI. Isolation and restriction
Infectious cases must be isolated until no longer infectious (see section 4: Timeline). Advice from the facility's infection control professional should be sought. Health care workers and others who come into contact with the case must use airborne, droplet, contact and standard infection control precautions (plus eye protection if within 1m). The mode of transmission is unclear, but postulated to be mainly droplet and direct contact. However, the possibility of airborne transmission remains, and airborne precautions must be used. If hospitalised, patients should be managed in a single room with airborne, droplet, contact and standard precautions and if available, a negative pressure room. Similarly, in a primary care setting such as a GP surgery, patient isolation and airborne, droplet, contact and standard infection control precautions should be employed. Cases may be managed at home only if the case and contacts are counselled about risk, infection control measures are made available and are in place, and a comprehensive discharge plan has been made by the treating hospital medical team in liaison with the PHU. Environmental evaluation
Where local transmission of AI is thought possible, a thorough review of contributing environmental factors should be done. If transmission is thought to be poultry-related, the environmental assessment should include a review of opportunities for exposure to infected birds, in collaboration with DPI and WorkCover NSW. If health care-associated infection is suspected, the adequacy of infection control procedures must be reviewed. Staff conducting the environmental evaluation must have a thorough understanding of infection control practices, be competent in using personal protective equipment (PPE), and have been vaccinated with the current (human) influenza vaccine. They must follow airborne, droplet, contact and standard infection control precautions, including appropriate PPE (gown, gloves, protective eyewear and P2 mask). Contact management
Identification of contacts
AI is not easily transmitted between humans and the only reports to date where human-to-human transmission has been suggested has involved close and prolonged contact. Until more evidence emerges, the public health intervention will need to be carefully considered on a case-by-case basis. Following a report of any suspected case, the NSW AI Expert Panel will be convened by CDB to help plan the public health response, including identification of contacts. Chemoprophylaxis
Antiviral medications may have efficacy in preventing diseases in contacts. Unless the available evidence clearly shows lack of efficacy, close contacts of confirmed cases should receive anti-influenza medication (neuraminidase inhibitors - oseltamivir and zanamivir) to prevent infection. Education
Contacts should be counselled about their risk and the symptoms of AI and placed under surveillance (see "Avian influenza ("bird flu") advice for people under surveillance" in appendices). The PHU should ensure that contacts are contacted on a daily basis for 7 days to determine if symptoms of AI have developed. If symptoms develop, the PHU should arrange assessment by an appropriately qualified medical practitioner. This must take place in a setting where risk is managed through the use of appropriate infection control precautions. Isolation and restriction
Contacts are not required to isolate themselves from the community but must adhere to advice regarding self-monitoring until the incubation period expires. Symptomatic contacts must be rapidly isolated until AI is excluded.
6. Managing special situations
Where DPI reports an outbreak of AI in birds in NSW, the PHU has the responsibility of ensuring that the risk of human infection is minimised. The public health actions should be guided by the NSW AI Expert Panel, which will be convened by CDB in collaboration with the PHU. Issues to be addressed include:
- Working with DPI and WorkCover NSW to ensure that people entering the area deemed by DPI to harbour infection have been trained in the use of PPE, and use it where the potential for exposure to infected birds or the dust from infected birds is present.
- Providing oral and written information to people who were exposed to the infected birds about the risk of infection, the methods of minimising the risk, symptoms to be alert for, and to report to the PHU immediately, should symptoms occur.
- Assessing whether people who were exposed to infected birds require anti-influenza medicine, and if so arranging supply (via CDB) and administration of the medicine. Indications for anti-influenza medicines will be determined by the AI Expert Panel, and may be limited to persons with direct exposure to infected birds in the absence of appropriate PPE.
- Placing exposed people under surveillance for seven days as per Section 5. Should symptoms develop, the PHU should arrange for a medical assessment and diagnosis of the person.
- The local Health Service Functional Area Co-ordinator (HSFAC) can assist in logistic issues.
Avian Influenza in Humans Reporting - Appendices
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