Bird Flu Alarm

Understanding Avian Influenza


Fever >38 C, cough +/- sputum.
Other common symptoms - sore throat, rhinitis, muscle aches, diarrhoea.
Progression to pneumonia occurs early, breathlessness.
Asymptomatic infections seen in HK and Japan.

Infectious Period
Generally, 1 day before onset of symptoms to 5 days in adults and 3 weeks in young children.
Infectiousness related to amount of viral shedding.
Viral shedding correlated with severity of illness.
Minimal symptoms, asymptomatic can still be infectious.

To build immunity against infections
Human vaccine against H5N1 avian flu under development.
To be effective, need close match with actual pandemic strain. First doses 4-6 months into pandemic (egg-based vaccine).
Clinical trials underway; commercial availability 2008.

Anti-viral Drugs
Four antiviral drugs available against influenza.
M2 inhibitors (amantadine, rimantadine) not effective against H5N1
Neuraminidase inhibitors (oseltamivir, zanamivir) probably effective (in-vitro and animal studies)
Zanamivir (Relenza) ? oral inhalation.
Oseltamivir (Tamiflu) ? oral capsules/syrup.
Can be used for treatment and prevention.

Treatment for 5 days.
Prevention only as long as drug is taken.
Must be given early (within 2 days) to be effective. Reduces duration of symptoms by 1-2 days. About 40-50% effectiveness in reducing likelihood of developing pneumonia.
For prophylaxis, about 80-90% effective in preventing disease.

Understanding Avian Influenza