The avian influenza or bird flu has been in the news for some time now. From time to time we come to learn of how a parrot died of the deadly H5N1 strain of the influenza virus in UK or how migratory birds have been dying in large numbers in Siberia or China. Side by side we also get sporadic news of a human being dying of this flu in Indonesia or in Vietnam. Experts have also been talking of the threat of a global influenza epidemic (or pandemic) and there is news of how Tamiflu (an influenza medicine) stocks are being sold out in many countries.

Potential vaccine shortage

At present the Government of India has stock of 20,000 doses of the anti-avian flu vaccine supplied by WHO.

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All of us are familiar with influenza having had influenza more than once in our childhood. Influenzas are usually characterized by fever, sore throat or cough, running nose and red eyes. Ordinary flu is self limiting and gets cured in about a week, whether you take medicine or not. From our childhood, most of us may also remember having been told that if you take medicines you will get cured in one week, otherwise it will take seven days for you to get okay. (Translated from a common Hindi saying that goes dawai loge tho ek saptah, dawai nahi loge tho saat din!)

Why is there such a hue and cry over such a simple and common ailment?

Influenza is caused by the influenza virus. There are many kinds of influenza virus, and those which affect human beings usually get transmitted through droplet infection or through the respiratory tract. While in most cases 'flu' is relatively mild, it can also assume severe forms. This is particularly so when the influenza virus is a new one. As a rule, most of us have developed some kind of immunity over the years to the common influenza virus. Even then, the very young or old, or those whose immune system is not robust may suffer complications from the common influenza virus as well. A particularly severe influenza pandemic occurred in 1918 (called the Spanish flu) when an estimated 40 million people died all over the world due to the disease. There have been two other flu pandemics in the last century – in 1957 and 1968 (the Asian flus), which took a lesser toll of lives.

Why the concern about bird flu?

According to the WHO, a flu pandemic occurs when three conditions are satisfied. First, a new influenza virus must emerge in the human population to which everyone is susceptible, second, it must be easily transmitted from one person to another and finally it should be able to cause serious illness. It is based on these three criteria that there is concern that the avian flu that has emerged in Southeast Asia may well transform itself into the next flu pandemic.

The avian flu that is in the news is a contagious disease that commonly occurs in birds and sometimes in humans and pigs. It is caused by a type A influenza virus and many are now familiar with its specific type -- H5N1. The disease may occur in a mild form or a severe form. It may start as a mild illness but after some months, due to changes in the virus, the disease may become serious and rapidly kill nearly all the affected birds. Hence the name, Highly Pathogenic Avian Influenza (HPAI). The present avian flu epidemic is severe. It is affecting domesticated poultry (chicken, turkey and eggs from infected birds) plus ducks, pigs, tigers and human beings in some countries.

This avian flu virus is (currently) not easily transmitted from birds to humans and all the persons whose death has been due to avian flu came in close contact with infected birds. Humans get infected from handling the birds or any material which is contaminated by the bird faeces. The virus may enter the respiratory tract by a simple act like rubbing your nose using your hand which may have held poultry. From 1997, when this current virus was first described in Hong Kong, till 14 November, a total of 126 human beings were affected and 64 succumbed.

The number of fatalities may not be of pandemic proportions, but there are a couple of things happening to the virus in the last eight years that has caused experts to raise the alert.

First, the virus is changing its virulence or ability to infect. Earlier it caused disease in poultry, but did not cause the disease in wild ducks. Ducks were asymptomatic carriers. But now, these ducks are dying in large numbers. There is evidence that wild birds and mammals are also dying in large numbers from this virus. Cats, which were earlier thought immune to the disease have also been found to be affected. There is also suspicion of human to human transmission in a few cases. All this clearly points to the fact that the virus is changing its character. The ability of a virus to change its character is itself well known. It does this either by mutation or by reassortment (incorporating human genetic material which will make virus replication in human beings easier).

Dr Samlee Plianbangchang, WHO Regional Director for the South-East Asia Region has warned, "The threat of a pandemic is very real. It is no longer a question of if it will occur. It is now only a question of when." He also pointed out that two of three pre-requisites to start any influenza pandemic have already been met. These are the emergence of a new virus to which all are susceptible and that the new virus is able to replicate and cause disease in humans. The third pre-requisite, which has not yet happened, is the ability of the new virus to be transmitted efficiently among humans (i.e. human to human.)

Should we be worried in India?

India is recovering from a badly managed Japanese Encephalitis (JE) outbreak this year which hit U.P. and Bihar. Considering that JE has been around in the country for over twenty five years (i.e. it is not new), and JE prevention and control measures are better known, the recurring failure in arresting JE each year does not bode well for the country. However it would be worthwhile to review the current state of vulnerability and preparedness.

Early warning and detection

While India does have a system of disease notification, influenza is currently not among the list of notifiable diseases. Notifiable diseases have to be reported to health authorities by the attending doctor, so there is a check on both incidence and spread.

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