‘In the 20th century, three influenza pandemics killed over 40 million people – and many experts agree that a new pandemic may occur at any time. The Severe Acute Respiratory Syndrome (SARS) outbreak in 2003 clearly demonstrated the vulnerability of the interconnected world to the spread of infectious diseases.’ World Health Organization (WHO), 2005 Avian influenza or ‘bird flu’ has been in and out of the headlines since a dramatic outbreak made poultry ill in Hong Kong in 1997. Eighteen people also contracted the virus, which caused severe respiratory symptoms and six human deaths. Within three days the entire poultry population of Hong Kong – around 1.5 million birds – was destroyed and, says WHO, a pandemic was thus averted.
The trouble is, no one will ever know if they were right, or if the authorities overreacted. Is the threat really as great as many experts believe?
Bird flu was first identified in Italy more than 100 years ago. It is a disease of wild fowl, but it tends to affect them mildly – indeed, they can migrate hundreds of miles while suffering from the infection. Thus wild birds have the capacity to spread it to new countries.
The 1997 avian influenza (type H5N1) that re-emerged in 2005 seems to be especially virulent. It started in South-East Asia and has now become entrenched in domestic chickens and ducks in Vietnam, Indonesia, parts of Thailand, Cambodia, China and probably Laos. There have been human cases in several countries: Vietnam, Thailand, Cambodia, Indonesia and, most recently, China. These are all regions where some people live in cramped housing in close contact with their domestic fowl.
Migratory birds have taken the virus out of South-East Asia to Russia, Kazakhstan, Mongolia, Turkey and Romania. Several different diseases of animals can transfer to humans but normally only when there is unusually close contact: shared, cramped accommodation or occupational exposure (eg abattoir workers) or bites.
Person-to-person spread is therefore unusual and normal travellers are at low risk.
The big concern with the H5N1 bird flu virus – and with all strains of influenza – is that it has the potential to mutate and transform into a human disease capable of transmission between humans.
One of WHO’s recommendations is that people who are in close contact with poultry should be immunised against the current strains of influenza. It is hoped that this will avoid simultaneous infection with human and bird flu, depriving the viruses of opportunities to exchange genetic material and become more dangerous to people. It was heartening to discover that cases of bird flu reported in Essex demonstrated that quarantine precautions are effective.
Our best defence against the spread of flu is prompt responses by public health authorities to outbreaks, so it is reassuring that WHO is taking this so seriously. Effort is going into developing vaccines too. However a new vaccine takes four months or so to produce, and viruses can then foil vaccine production by mutation.
There are currently four anti-viral drugs that are some help in treatment of influenza: the older amantadine and rimantadine, which are only effective against influenza A, and the recently developed oseltamivir (Tamiflu) and zanamivir (Relenza). These last two are taken for four to seven days and work best if started within hours of the beginning of the illness, but definitely within 48 hours. They can also be taken to prevent infection after being exposed to the virus.
Over 30 million doses of Tamiflu have been taken – mostly in Japan – and there have been some reports of nasty side effects including abnormal behaviour, confusion and hallucinations, as well as two suicides that may be associated. While a number of my patients are clamouring to get Tamiflu capsules, I have simply been immunised against ‘ordinary’ flu and await developments.
Pandemics are rare but recurrent phenomena: in 1918 about 40 million people died from Spanish flu; the next pandemic (Asian flu, 1957) killed about two million; the 1968 Hong Kong flu killed around a million. In the pre-jet age, the flu virus took six to nine months to spread throughout the globe; the next one – it is predicted – will take three.
While WHO are forecasting ‘the next pandemic’, we can be confident that the risks to ordinary travellers will be small. It is still best to focus on accident prevention, safe sex and being properly insured; these issues are more important in protecting health, and a higher priority than wondering where you can acquire your own supplies of Tamiflu.
And there’s no point asking your GP for a prescription, just in case: we can’t get it. We’re not even supposed to prescribe it privately and, in the UK, pharmacists can’t get hold of it.
If you want more up-to-the-minute information on bird flu or other outbreak news check the WHO (www.who.int) and the Center for Disease Control and Prevention (CDC; www.cdc.gov) websites – although they make scary reading.
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