Background: Pandemic influenza (H1N1) 2009 is susceptible to oseltamivir. There are few reports on its clinical and virologic response to oseltamivir.
Methods: During the pandemic containment response in Singapore, all patients with positive polymerase chain reaction (PCR) results for pandemic influenza (H1N1) 2009 were hospitalized, given oseltamivir for 5 days, and discharged when daily PCR results for combined nasal and throat swab samples became negative. Six patients had concurrent positive viral culture and PCR results.
Results: The median age of the first 70 consecutive patients was 26 years (interquartile range, 21-38 years); 60% were men, and 29% had comorbidity. The mean time (+/-SD) from illness onset to hospital admission was 3+/-2 days. Influenza-like illness was noted in 63% of patients. Fever occurred in 91%, cough in 88%, sore throat in 66%, and rhinorrhea in 53% of patients. The mean duration (+/-SD) of viral shedding from illness onset was day 6+/-2 days. Viral shedding persisted beyond 7 days in 37% of patients. Clinical features and viral shedding were similar between those with and without comorbidity, except the former had more cough and lower oxygen saturation. Patients receiving oseltamivir on days 1 to 3 of illness had significantly shorter viral shedding duration, compared with those treated from day 4 onwards (P < .05). The mean durations (+/-SD) of positive PCR and viral culture results were 5+/-8 and 4+/-18 days, respectively, for 6 patients with concurrent positive viral culture and PCR results.
Conclusions: Prolonged viral shedding was noted in young immunocompetent adults with mild pandemic influenza (H1N1) 2009 despite receipt of oseltamivir. When prescribed during the first 3 days of illness, oseltamivir shortened the duration of viral shedding.