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What is avian influenza?
Avian influenza bird flu is an infection caused by the bird flu viruses, which occur naturally among birds. Wild birds are carriers of the bird flu viruses, which are found in their intestines. However, these birds themselves do not get sick from them. Nonetheless, avian influenza bird flu is easily transmittable among birds. This virus can also pass on to domesticated birds, which include chickens, ducks, and turkeys.
Infected birds shed the influenza virus in their saliva, nasal secretions, and faecal droppings. Susceptible birds become infected when they come in contact with contaminated secretions or excretions. Moreover, domesticated birds can also become infected with avian influenza virus through direct contact with infected waterfowl or poultry, through contact with infected surfaces, or materials that have been contaminated with the avian influenza virus.
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Infection with avian influenza viruses in domestic poultry causes two main forms of disease that is the mild pathogenic form and the highly pathogenic form. The “mild pathogenic” form may usually go undetected and cause only mild avian influenza symptoms like ruffled feathers and a drop in egg production. However, the highly pathogenic form has the potential of spreading rapidly through poultry flocks. It can affect multiple internal organs and has a mortality rate that can reach 90-100% within 48 hours.
Avian influenza virus does not usually infect humans, but there have been several cases of human infection since 1997. It is believed that most cases of bird flu infection in humans have resulted from contact with infected poultry or contaminated surfaces. There is no evidence of human-to-human transmission so far.
Migratory birds may or may not carry the avian flu virus. It depends on whether these birds have flown from a region where avian flu is prevalent. As a precaution, humans should stay away from these birds and their droppings.
What drugs are available for treatment?
Avian influenza bird flu is difficult to diagnose through symptoms alone. Therefore, a laboratory test must be conducted. Avian influenza is usually diagnosed by collecting a swab from the nose or throat during the first few days of the illness. This swab is then tested at a laboratory for the avian influenza disease. If it is late in the illness, it may be difficult to find an avian influenza virus directly using these methods. In this case, a diagnosis is made by looking for evidence of the body’s response to the virus. This procedure requires two blood specimens and it can take several weeks to verify the results.
There is no effective treatment for avian influenza. However, good husbandry, proper nutrition, and broad spectrum antibiotics may reduce secondary infections. It must be remembered that recovered flocks continue to intermittently shed the virus.
Avian influenza bird flu in humans can be treated with antiviral drugs that are clinically effective in both preventing and treating the disease. Vaccines, however, take at least four months to be made and must be prepared for each subtype. Once the disease has been detected and reported, stringent disease control measures must be taken.
An antiviral medication, oseltamivir (Tamiflu), manufactured by Roche Laboratories, is used as a treatment for influenza A virus, and as a prophylaxis within 48 hours of exposure. Studies to date suggest that these prescription medications approved for human influenza strains can effectively prevent avian influenza infections in humans. However, sometimes avian influenza virus strains can become resistant to these drugs and therefore may not always be effective.
Amantadine and rimantadine are the M2 inhibitors whereas oseltamivir and zanamivir are the neuraminidase inhibitors. These drugs have been licensed for the prevention and treatment of human influenza in some countries, and are thought to be effective regardless of the causative strain. However, analysis of viruses isolated from the recently fatal cases indicates that the viruses are invariably resistant to the M2 inhibitors. Network laboratories are also conducting studies to confirm the effectiveness of neuraminidase inhibitors against the current H5N1 bird flu strains.
Current avian influenza vaccinations, when administered to high-risk groups such as poultry cullers, protect against circulating human strains and thus reduce the risk. Dual infections in birds and humans give the avian and human viruses an opportunity to exchange genes, possibly resulting in a new influenza virus subtype with pandemic potential. Seasonal epidemic influenza vaccines, however, offer no protection against infection with the H5N1 bird flu virus – it will need specific avian influenza vaccine.
Tamiflu to treat avian influenza
Two main risks for human health from avian influenza are:
- The risk of direct infection when the virus passes from the infected bird to humans, sometimes resulting in severe disease; and
- The risk that the virus – if given enough opportunity – will change into a form that is highly infectious for humans and spread easily from person to person.
Tamiflu Oseltamivir can be used for treating people aged 1 year or older, who are infected with the human or avian influenza virus. However, this medication is most effective when it is started within 48 hours (2 days) of starting to feel unwell. The earlier it is started after the onset of symptoms, the more effective it will be.
Oseltamivir is a neuraminidase inhibitor that helps prevent the influenza virus from spreading inside the body. If started within 48 hours of the first influenza symptoms, these medications can reduce the severity of symptoms as well as the time taken to recover from the illness.
Oseltamivir can also be used to prevent getting influenza in those who have been exposed to the people who have recently become ill with influenza. Oseltamivir can be used to prevent influenza in people aged 13 years and older if the appropriate influenza vaccine is not available.
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Oseltamivir is an oral prescription medication that comes in a capsule form for adults and as a suspension for children. The dosage in adults without severe kidney problems is:
- One capsule twice a day for 5 days when used to treat influenza, and
- One capsule daily for at least 7 days when used to prevent getting influenza.
You should not take Oseltamivir if you are allergic to this medication, or to any of the medication ingredients. Before starting treatment, tell your doctor about other medications you may be taking. You should also tell your doctor if you have any chronic or serious illnesses, in particular if you have kidney disease, asthma or lung disease, as special precautions may be needed.
Overall, this neuraminidase inhibitor is very safe. The most common side effects include nausea, vomiting and other gastrointestinal symptoms. However, these affect less than 1 in 10 people. Taking the medication with food may help reduce or prevent thee side effects.
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