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H1N1 Oseltamivir treatment can begin before lab confirms infection: WHO

Wednesday, August 26, 2009, 8:19 This news item was posted in Featured category and has 0 Comments so far.

Healthy patients with uncomplicated illness need not be treated with antivirals

Oseltamivir (Tamiflu) treatment for swine flu causing H1N1 influenza A virus should start immediately and not wait for laboratory confirmation for the virus, in areas where the virus is circulating widely in the community, recommmends WHO in its latest guidelines for use of antivirals against H1N1 infection.

Doctors seeing patients with influenza-like illness should assume that the pandemic virus is the cause in areas where the virus is circulating widely in the community and treatment decisions should not wait for laboratory confirmation of H1N1 infection.

World Health Organisation (WHO) has issued guidelines for the use of antivirals in the management of patients infected with the H1N1 pandemic virus.

The guidelines represent the consensus reached by an international panel of experts who reviewed all available studies on the safety and effectiveness of these drugs. Emphasis was placed on the use of oseltamivir and zanamivir to prevent severe illness and deaths, reduce the need for hospitalization, and reduce the duration of hospital stays.

H1N1 pandemic virus is currently susceptible only to oseltmivir (Tamiflu) and zanamivir (Relenza) which belong to the classs of antiviral drugs known as neuraminidase inhibitors. H1N1 is resistsnt to a second class of antivirals – the M2 inhibitors.

Treatment with oseltamivir should begin as soon as possible for patients who initially present with severe illness or whose condition begins to deteriorate,Studies show that early treatment, preferably within 48 hours after symptom onset, is strongly associated with better clinical outcome.

Oseltamivir, when properly prescribed, can significantly reduce the risk of pneumonia – a leading cause of death for both pandemic and seasonal influenza – and the need for hospitalization, indicates evidence reviewed by the WHO panel.

For patients with severe or deteriorating illness, treatment should be provided even if started later. Where oseltamivir is unavailable or cannot be used for any reason, zanamivir may be given.

Treatment should be based on clinical assessment and knowledge about the presence of the virus in the community, WHO recommends saying that these recommendation is supported by reports, from all outbreak sites, that the H1N1 virus rapidly becomes the dominant strain.

All patient groups, including pregnant women, and all age groups, including young children and infants can be treated in this way.

Pregnant women receive antiviral treatment as soon as possible after symptom onset, as they are included among groups at increased risk.

Treatment with either oseltamivir or zanamivir is recommended for patients with underlying medical conditions that increase the risk of more severe disease. These patients should also receive treatment as soon as possible after symptom onset, without waiting for the results of laboratory tests.

Worldwide, most patients infected with the pandemic virus continue to experience typical influenza symptoms and fully recover within a week, even without any form of medical treatment. Healthy patients with uncomplicated illness need not be treated with antivirals.

However, H1N1 infection can get complicated in patients with underlying chronic disease, including asthma, chronic obstructive pulmonary disease, chronic hepatic or renal failure, diabetes or other cardiovascular conditions.

At the same time, the presence of underlying medical conditions will not reliably predict all or even most cases of severe illness. Worldwide, around 40 per cent of severe cases are now occurring in previously healthy children and adults, usually under the age of 50 years.

H1N1 infection can turn complicated in some of these patients suddenly, usually on day 5 or 6 following the onset of symptoms.

In cases of severe H1N1 illness, clinicians may consider using higher doses of oseltamivir, and for a longer duration, than is normally prescribed.

Major complications are viral pneumonia, which destroys the lung tissue and does not respond to antibiotics, and the failure of multiple organs, including the heart, kidneys, and liver. These patients require management in intensive care units using therapies in addition to antivirals.

Shortness of breath, either during physical activity or while resting; difficulty in breathing; turning blue; bloody or coloured sputum; chest pain; altered mental status; high fever that persists beyond 3 days; low blood pressure are some of the symptoms of major complications with H1N1 infection.

Clinicians, patients, and those providing home-based care need to be alert to warning signals that indicate progression to a more severe form of illness, and take urgent action, which should include treatment with oseltamivir.

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