Prevention key to containing new avian flu outbreak

The unexpected outbreak of influenza A(H7N9) on the mainland marks the first time the virus has been detected in humans. By last night, there were 18 confirmed cases, of which six have been fatal.

Until more information is available, clinical understanding of the disease behaviour of H7N9 infections remains incomplete. So far, it is believed that the primary risk factor for human infection appears to be direct or indirect exposure to infected live or dead poultry or contaminated environments.

Drawing from previous experience with H5N1 and other strains of influenza, initial symptoms could include a high fever, and other flu-like symptoms such muscle cramps, sore throat, cough, loss of energy, breathlessness, diarrhoea, vomiting, abdominal pain and chest pains.

In the face of such a devastatingly infectious disease, prevention is key.

Hong Kong's proximity to the mainland and its role as a global nexus puts it in a particularly delicate position. Visitor health screening should be strongly considered and implemented judiciously. As well, hospitals and clinics should be bolstered with H7N9 testing; health care personnel placed on high alert for suspicious cases and stockpiles of antivirals be updated and assured.

There has been no human-to-human transmission, the advent of which is crucial to a pandemic alert.

Avian influenza, or bird flu, is an infectious disease of birds caused by viruses of the same family that causes the "flu" in humans. They are, however, not identical and have important genetic distinguishing features. Normally, avian influenza viruses do not infect humans. But every now and then, these viruses and human influenza A viruses converge in a host (fowl or mammal) and reassemble into a new strain. This drastic form of mutation is known as "antigenic shift". The new strain is more lethal and very transmissible due to the nature of poultry farming and an interconnected world. Worse, due to their novelty, these viruses are usually not covered by the annual vaccine profiles. In the past decade, one such dreaded strain, H5N1, alerted the world to just how catastrophic an antigenic shift could be. Since its first outbreak in Hong Kong in the late '90s, it demonstrated widespread re-emergence in 2003 and 2004, spreading from Asia to Europe and Africa, has become entrenched in poultry and continues to claim lives.