AVIAN INFLUENZA

Background

Influenza viruses type A, B and C are among the causes of respiratory tract infections in humans. Type A virus has 15 subtypes some of which are predominant in pigs (swine influenza virus), in humans (human influenza virus), in horses (equine influenza virus) or in birds (avian influenza virus)1.

Human and animals can pass influenza virus from one to another. Humans can thus, become sick from avian or swine influenza when they pick up the virus from these animals2.

In irregular intervals which can be as frequent as yearly, genetic particles of viruses from birds and pigs or humans are mixed (assortment) to produce novel subtypes with increasing virulence. The theory of the pandemic flu is derived from the expectation that such a mixture of viral materials will produce a novel influenza that will spread early in humans unhindered by a non-existent human immunity3.

Influenza A viruses are classified into subtypes based on two surface proteins, the hemagglutinin (HA) and neuraminidase (NA). A virus that has a type 1 HA and type 2 NA, for example, would have the subtype H1N2. At least 16 types of hemagglutinins (H1 to H16), and 9 neuraminidases (N1 to N9) are known to exist in birds4.

Transmission

Symptoms

The symptoms of swine influenza and avian influenza in people are similar to the symptoms of regular human seasonal influenza infection and include:

  • Fever
  • Conjunctivitis
  • Fatigue
  • Lack of appetite
  • Coughing
  • Sore throat
  • Vomiting and diarrhea.
  • Muscle ache

However, it is important to note that infection with a HPAI virus if untreated can result into a multi-organ disease including acute respiratory illness and neurologic disorder 12.

Diagnosis/Testing

Diagnosis of Human Avian Influenza infection is done through isolation of viral particles in culture of respiratory secretions (throat and nasal swab inclusive). However this technology is often not available in developing countries. It is also highly biohazardous. Commercial rapid tests which are easily applicable in the field are less sensitive.

The most used diagnostic method is real time polymerase chain reaction RT-PCR13,14, a molecular method alternative that reduces the challenges inherent in viral culture process.

Treatment

Antiviral drugs Oseltamivir, Peramivir, and Zanamivir have been successful in treatment of Avian Influenza A viruses. However, some evidence of antiviral resistance has been reported in HPAI Asian H5N1 viruses and influenza A H7N9 viruses isolated from some human cases 12.

PREVENTION & CONTROL:

Prevention and control strategies for Avian Influenza include the following:

In Humans

 Vaccination

Taking annual seasonal influenza vaccination is recommended to protect against seasonal influenza virus. This might not protect against any new strain15.

 Infection prevention practices

  • Those responding to or working with poultry should wearing personal protective equipment while working in communities with existing outbreak.
  • Eat well cooked poultry and poultry products.
  • Practice good hand hygiene

 Public Education

  • Include self-monitoring for illness during and after responding to HPAI outbreaks among poultry.
  • Increase surveillance
  • Engender societal behavioural changes

In Poultry farms

 Disinfection

 Vaccination of birds

 Infection prevention practices

  • Culling infected poultry farm birds
  • Proper disposal of death birds.

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