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Early oseltamivir use shortens shedding of H1N1 virus

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – Patients with the H1N1 virus who started oseltamivir in the first 3 days of illness had shorter periods of viral shedding, according to an observational study reported in the April 1st issue of Clinical Infectious Diseases.

The data are from the first 70 consecutive patients admitted to Singapore’s Tan Tock Seng Hospital in the spring of 2009 for PCR-confirmed H1N1 infection. All subjects received oseltamivir for 5 days and were discharged when nasal and throat swab PCR results were negative.

Dr. David C. Lye and colleagues report that their median patient age was 26 years, 60% were men, and 29% had comorbidities. Sixty-three percent had influenza-like illnesses, 91% had fever, 88% had cough, 66% had sore throat, and 53% had rhinorrhea. On average, patients entered the hospital 3 days after illness onset.

Viral shedding continued for an average of 6 days after illness onset. In 37% of patients, shedding lasted beyond 7 days.

Besides having more cough and lower oxygen saturation, patients with comorbidities were comparable to patients without them in terms of clinical features and viral shedding.

Early treatment with oseltamivir seemed to shorten the duration of viral shedding. Twenty-two percent of patients treated within 1 to 3 days of onset were shedding virus at 7 days, compared with 53% who received the drug later (p < 0.01).

On the other hand, oseltamivir therapy starting on or after day 4 “was associated with more prolonged viral shedding.” The median duration of shedding was 5 days when therapy started within 3 days of illness onset, 7 days when therapy started on day 4, and 8.5 days when therapy began on day 5 or later.

“In contrast to randomized controlled trials showing earlier alleviation of symptoms for oseltamivir and zanamivir given in the first 2 days of illness…we did not observe earlier resolution of fever or respiratory symptoms in our patients who received oseltamivir within the first 2 days of illness,” the authors said.

“Our findings call into question the clinical benefit of oseltamivir therapy for acute uncomplicated pandemic (H1N1) 2009 infection,” they add. “However, our study was small and unrandomized.”

They conclude: “Further research on viral shedding in untreated patients with mild illness, treated patients with severe illness and surveillance for the emergence of oseltamivir resistance should be considered.”

Reference:

Clin Infect Dis 2010.