Highly pathogenic avian influenza

Part of the Communicable Disease Control Manual

Chapter last reviewed and updated in May 2012.

Contents


Epidemiology in New Zealand

Highly pathogenic avian influenza (HPAI) is caused by a genetically distinct strain of the influenza A subtype H5N1. Although human-to-human transmission of the HPAI H5N1 strain has been limited, emergence of HPAI outbreaks in domestic poultry, high rates of death in infected poultry and a 60 percent case-fatality rate in infected humans are significant causes for concern.

Note: Highly pathogenic avian influenza is a separate notifiable disease to non-seasonal influenza. A separate chapter relates to non-seasonal influenza.

More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website.

Case definition

Clinical description

Rapid onset of respiratory and generalised signs and symptoms of influenza, which can include fever, chills, sweating, a cough and a sore throat.

Laboratory tests for diagnosis

Laboratory confirmation requires identification of H5N1 virus by at least one of the following:

  • real-time reverse transcriptase polymerase chain reaction (RT-PCR)
  • viral culture
  • four-fold rise in H5N1 virus-specific neutralising antibodies.

Case classification

  • Under investigation: A person who has been referred to the public health service for investigation of possible HPAI infection.
  • Suspected: A clinically compatible illness in a person who, in the 7 days before the onset of symptoms, did one or more of the following:
    • was in an area where HPAI infections (in animals or humans) have been suspected or confirmed in the last month
    • consumed raw or undercooked meat from known source animals in an area where HPAI infections have been suspected or confirmed in the last month
    • had close contact with suspected or confirmed HPAI-infected animals
    • was working in a laboratory that is handling samples from people or animals that are suspected of HPAI infection.
  • Probable: A clinically compatible illness with a strong epidemiological link to a confirmed case or defined cluster.
  • Confirmed: A person with laboratory-confirmed HPAI infection.
  • Not a case: A case that has been investigated and subsequently found not to meet the case definition.

Spread of infection

Incubation period

A range of 1–4 days; however, person-to-person transmission of HPAI is currently rare.

Mode of transmission

Predominantly from source animals (birds, pigs) through exposure to infected body fluids or undercooked meat.

Period of communicability

Unknown.

Notification procedure

Attending medical practitioners must immediately notify the local medical officer of health of suspected cases of HPAI.

Laboratory notification of suspected cases of HPAI should be made directly to the Ministry of Health, preferably by telephone. This should be followed by a written (electronic) notification on confirmation.

Management of cases and contacts including other control measures

The health sector response to the New Zealand emergence of any cases of HPAI is guided by the New Zealand Influenza Pandemic Action Plan (Ministry of Health 2010).

Note: A close contact is a person who has cared for, lived with, or had direct contact with respiratory secretions or bodily fluids of a probable or confirmed case

Reporting

Ensure complete case information is entered into EpiSurv.

On receiving a notification, medical officers of health should immediately notify the Ministry of Health, including the Director of Public Health.

The International Health Regulations (IHR) National Focal Point (NFP) in the Ministry must notify the World Health Organization (WHO) of events involving any case of smallpox, poliomyelitis, severe acute respiratory syndrome (SARS) or human influenza caused by a new subtype. The NFP must also use the IHR Decision Instrument for any event involving cholera, pneumonic plague, yellow fever, viral haemorrhagic fevers, West Nile fever or any unusual or potentially serious public health event, and then notify WHO if required.

References and further information

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