New Study Indicates That Even Delayed Treatment With Oseltamivir Improves Survival In Patients Infected With Avian Influenza (H5N1)

A study published in the Journal of Infectious Diseases indicates that treatment with oseltamivir significantly reduces mortality in patients with influenza A/H5N1, or 'bird flu', even when given late in the course of illness.


In humans, influenza A/H5N1 is associated with severe disease and a high mortality rate.1 The multinational observational study, which is the largest-ever analysis of confirmed influenza A/H5N1 cases, showed a survival rate of 50% in patients who received oseltamivir within six to eight days after the onset of their influenza symptoms, compared with 29% in patients who did not begin antiviral treatment during the same time period. In addition, these data, collected from 308 A/H5N1 patients occurring between 1997 and 2009 in 12 countries, showed oseltamivir was even more effective when treatment was started soon after symptom onset, with approximately 80% of patients surviving when oseltamivir was administered within two days of symptom onset compared to 20% survival for those who were untreated.


Prof Wiku Adisasmito from the University of Indonesia and lead author notes:


"This important study highlights a new finding, that even delayed treatment with oseltamivir offers benefits. Clearly early treatment is what clinicians should aim to initiate and retain a high index of suspicion, but if presentation or diagnosis is delayed, treatment should still be started with oseltamivir. This study also highlights the benefits of the aggregation of data derived from many cases from multiple sites."


Nancy Dreyer, Principal Investigator and Chief of Scientific Affairs for Outcome commented: "Influenza A/H5N1 continues to pose a threat to public health because of its widespread presence in birds. Given its ability to cause severe disease and high mortality, and to crop up unexpectedly, it is critical that we are prepared to have the means to cope with this. This study has shown that oseltamivir continues to work effectively against this strain and reinforces the benefits of ensuring patients presenting with influenza symptoms are promptly diagnosed and treated. It also shows a treatment benefit even when treatment initiation is delayed."


Notes
About avian influenza A(H5N1)


The first human outbreak of Influenza A/H5N1 or avian influenza was detected in Hong Kong SAR and since then, more than 500 cases have been reported. Most human cases result from exposure to infected poultry; however, there is a persistent danger that if virus adaptation leads to increased human to human transmissibility, it could trigger a global pandemic with high associated health and economic costs.


About the Avian Flu Registry


The Avian Flu Registry is a one of a kind global database collecting detailed information on clinical presentation, treatment, and course of human influenza A/H5N1 from 12 countries. It is designed as a collaborative study involving members of the international scientific and medical communities interested in better understanding the clinical course and effectiveness of current treatments of avian influenza in humans. The Registry contains information on nearly 70% of World Health Organization confirmed cases of H5N1. The Registry is led by Outcome Sciences, Inc. (d/b/a Outcome) with collaboration from physicians and epidemiologists from Azerbaijan, Hong Kong, Indonesia, Nigeria, Pakistan, Thailand, Turkey and the UK. Data collection is continuing. The registry is funded by a contract from Hoffmann-La Roche.


About the study


The study is an observational study of laboratory-confirmed H5N1 infection. No treatments were prescribed or provided for this study. Instead, what doctors actually used for treatment was recorded for study purposes, along with whatever information that was available about the patients symptoms and survival.


- Data on cases were obtained primarily from clinical records, published cases series and governmental agency reports


- 308 cases occurring between 1997 - 2009 were identified from 12 countries; Azerbaijan, Hong Kong, Nigeria, Pakistan, Turkey, Egypt, Indonesia, Bangladesh, Cambodia, China, Thailand and Vietnam


- 150 subjects received oseltamivir only, two received ribavirin in combination with oseltamivir and one received rimantadine in combination with oseltamivir


- Overall, the median age of cases was 17 years (range: 1 - 75 years); 46%