Bird flu: Not just a flu

Influenza or more simply flu, is a respiratory disease caused by a group of viruses. It can attack human beings and certain animals. Normally, people are infected only by the human influenza viruses, not by the animal or avian (bird) influenza viruses. Although avian influenza viruses usually do not infect human beings, several instances of human infections have been reported since 1997. On some occasions, animal influenza viruses, or viruses containing genes from animal influenza viruses can start infecting people. The bird flu is especially dangerous because our immune systems don't have any antibodies to handle something that used to be relegated to animals. Thus, it takes hold with unprecedented force, settles in the lungs, and resists anti-viral and anti-bacterial medication

These viruses evolve in two ways, through drift and through shift. Drift refers to inexact replication, such that newer viruses are further from the original genetic material, but share enough DNA that they are still only spread amongst a single species.

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When a virus shifts, it means that the genes of one virus mix, or breed, with a different virus, usually inside a carrier. Due to shift, bird flu mixed with a human kind of flu, and was thus able to infect humans through direct contact with birds.

When a completely new strain of influenza virus emerges among human populations with the ability to spread easily from person to person, the virus can spread world wide within months and even weeks, leading to a higher level than usual of mortality and severe illness. In this situation, all age groups are vulnerable to infection, and there can be disruption of all sectors of the society. Such a situation is called influenza "pandemic." Pandemics are different from usual influenza seasons and happen relatively infrequently.

Symptoms of avian influenza in humans
The reported symptoms of avian influenza in humans have ranged from no symptoms, typical influenza-like symptoms, e.g., fever, cough, sore throat, and muscle aches, to eye infections (conjunctivitis), pneumonia, acute respiratory distress, viral pneumonia, and other severe and life-threatening complications

Why bird flu is a threat
The bird flu is especially dangerous because our immune systems don't have any antibodies to handle something that used to be relegated to animals. Thus, it takes hold with unprecedented force, settles in the lungs, and resists anti-viral and anti-bacterial medication.

There is currently rising concern that an avian or bird influenza virus, known as avian influenza (AI), influenza A (H5N1) or simply as H5N1. The virus is circulating widely among birds, primarily in Asia but now also in parts of Europe, and may gain the ability to spread easily from person to person and lead to the first influenza pandemic of the 21st century. Many of the prerequisites for the start of an influenza pandemic appear to be in place, but the virus still has not gained the ability to conduct efficient and sustained human-to-human transmission. The possibility that the H5N1 virus will gain this ability must be considered quite "real" but also is not certain. Once the virus has gained the ability to spread easily among people, then no country or region can be considered as a low risk area for infection. In essence, there will be no "safe havens" from potential exposure to the virus. It is impossible to predict where and when, or if at all, an outbreak of the AI may occur. However, the rising concern over the H5N1 virus requires prevention and preparedness.

Spread of bird flu
The situation of AI is rapidly evolving in Asia as well as globally. Several countries are now already infected, e.g. Cambodia, China, Croatia, Indonesia, Kazakhstan, Laos, Mongolia, Pakistan, Russia, Thailand, Vietnam, Rumania, and Turkey. The list of infected countries is growing day by day, partly due to arrival of migratory birds or wild birds from infected countries. Even though till date there is no reported case of AI in the country, Bangladesh is considered as at risk along with other countries like India, Kyrghyzstan, Philippines, Morocco, Myanmar, Algeria, and Iran. Bangladesh is vulnerable to this disease as geographically the country lies on a major route of migratory birds. It is therefore crucial to take all curative and preventive measures in tackling the disease effectively in the event of its occurrence.

Anti-viral agents for influenza
Four different influenza antiviral drugs (amantadine, rimantadine, oseltamivir, and zanamivir) are approved by the US Food and Drug Administration (FDA) for the treatment of influenza; three are approved for prophylaxis. All four have activity against influenza A viruses. However, sometimes influenza strains can become resistant to these drugs, and therefore the drugs may not always be effective. Monitoring of avian influenza A viruses for resistance to influenza antiviral medications is ongoing.

If an influenza pandemic occurs, the following are expected:

1. Given the geographical location of Bangladesh in a high-risk region, neighbouring countries Myanmar, Nepal and India, which were bordering China, Thailand, and Laos, the pandemic virus of H5N1 could spread rapidly, leaving little or no preparation time.
2. The spring migration of birds of 2006 may result in the spread of HPAI H5N1 virus further across Europe since birds migrating from southern zones will have intermingled with European Russia and Siberia-origin birds during the 2005-2006 winter nesting areas.
3. Given the high level of global travel, the pandemic virus may spread to much of the world within weeks to months, leaving little or no time to prepare.
4. The health care workforce is likely to be reduced because health care workers also will become ill and will also stay home to care for ill family members.
5. For weeks at a time, significant shortages of personnel may occur, disrupting essential community services.
6. Vaccines and antiviral agents for pandemic influenza, and antibiotics to treat secondary infections will be in short supply initially, while distribution of available supplies is likely to be unequal. It will take several months or longer before any effective pandemic vaccine becomes widely available.
7. Many if not most medical facilities in Bangladesh will be overwhelmed by the overall response to the pandemic.

The writer is Program Officer, Migration Health, for an inter-governmental organisation.