The nine human cases of H5N1 avian flu identified in Cambodia during the past few weeks, which has resulted in death in eight of the cases, have ignited new fears about the possibility of a new flu epidemic with potentially serious public health and socio-economic consequences for Southeast Asian nations.
The presence of a new active spot of avian flu gives rise to three main issues: first, a public health issue linked to human contamination and the loss of life, which mainly affects chicken producers and sellers in fresh markets. Second, socio-economic and ecological issues related to the massive destruction of suspected poultry farms. Third, a potential epidemiological issue linked to the prolonged circulation of H5N1 virus, which increases the risk of viral mutation from the avian strain to a virulent human-to-human strain.
Fear of a resurgence of inter-human transmission comes from the past pandemics. The 1918 Spanish flu with its 18 million deaths, the Asian flu in 1957 (one million deaths) and the Hong-Kong flu in 1968 (800, 000 deaths) originated from human influenza flu viruses that acquired significant genetic material from bird flu viruses. Many scientists believe that the next major human flu epidemic could result from repeated and poorly controlled avian flu outbreaks, during which the spontaneous generic variability of the virus would lead to new dangerous human strains.
In Asia, the sporadic epidemics of avian flu started in 1997 with the highly publicised “chicken flu”. Since then, the epizootic flu disease has killed millions of domestic and wild birds and spread to Thailand in 2007-2008.
From 2003 to 2009, human cases of bird flu reached 403 people worldwide with 254 deaths. The majority of infected individuals were from the Asean countries and China with 321 cases and 218 deaths. The risk of contamination appears particularly low but the mortality rate remains extremely high, with up to 65 per cent of confirmed human cases failing to survive.
Compared to the seasonal flu however, these figures remain very low. In a country like France with 65 million inhabitants, the seasonal flu affects between 100,000 to 300,000 people every year and has an average mortality rate of 5,000 individuals, many of them often already suffering from severe chronic illnesses.
Even though the risk of viral mutation remains possible, human contamination by avian flu appears very unlikely in comparison to the seasonal flu infestation. The awareness of poultry producers and the rapid intervention of veterinarian services are essential to circumvent the development of new outbreaks.
The H5N1 flu incubation period lasts usually between two to eight days but may be up to two weeks. Following exposure to possibly contaminated birds, treatment in an intensive care unit must be initiated as soon as possible and, as with any flu syndrome, the patient needs to be isolated. The first and most common symptoms are high fever, cough, abdominal pain, vomiting, diarrhoea and breathing difficulties. Respiratory failure commonly occurs soon after as a result of pneumonia of viral origin, which does not respond to antibiotics. Death may occur from the sixth day onwards.
Antiviral medication, and particularly oseltamivir (Tamiflu), must be used within the first 48 hours following the initial signs. However, its benefit / risk ratio remains controversial. Preventive measures include avoidance of live poultry and common hygiene rules. It is worth noting that the seasonal flu shot does not provide protection against bird flu.
Dr Gerard Lalande is managing |director of CEO-Health, which provides medical referrals for expatriates and customised executive medical check-ups in Thailand. He can be contacted at firstname.lastname@example.org.