Severe Human Influenza Infections in Thailand: Oseltamivir Treatment and Risk Factors for Fatal Outcome

Abstract

BackgroundInfluenza is often not recognized as an important cause of severe or fatal disease in tropical and subtropical countries in Southeast Asia. The extent to which Oseltamivir treatment may protect against a fatal outcome in severe influenza infections is not known. Thailand's National Avian Influenza Surveillance (NAIS) system affords a unique opportunity to describe the epidemiology of laboratory-confirmed severe and fatal human influenza infections.Methodology/Principal FindingsDuring January 2004 through December 2006, 11,641 notifications to the NAIS were investigated in 73 of 76 Thai provinces. Clinical and demographic data and respiratory swab specimens were collected and tested by PCR for influenza. Using the NAIS database, we identified all patients with laboratory confirmed human influenza (A/H3N2, A/H1N1 and Type B) infection. A retrospective medical record review was conducted on all fatal cases with laboratory confirmed influenza and from a sample of hospitalized cases in 28 provinces. The association of underlying risk factors, Oseltamivir treatment and risk of a fatal outcome were examined. Human influenza infections were identified in 2,075 (18%) cases. Twenty-two (1%) deaths occurred including seven deaths in children less than ten years of age. Thirty-five percent of hospitalized human influenza infections had chest X-ray confirmed pneumonia. Current or former smoking; advanced age, hypertension and underlying cardiovascular, pulmonary or endocrine disease were associated with a fatal outcome from human influenza infection. Treatment with Oseltamivir was statistically associated with survival with a crude OR of .11 (95% CI: 0.04–0.30) and .13 (95% CI: 0.04–0.40) after controlling for age.ConclusionsSevere and fatal human influenza infections were commonly identified in the NAIS designed to identify avian A/H5N1 cases. Treatment with Oseltamivir is associated with survival in hospitalized human influenza pneumonia patients.

Correlates of severe disease in patients with 2009 pandemic influenza (H1N1) virus infection

“…tions of seasonal influenza, obesity 4 and other underlying comorbidities 3,5 may be risk factors for severe disease. The interval from onset of symptoms to initiation of antiviral therapy or other treatment and supportive care was also associated with adverse outcome in a recent case series.…”

Randomised controlled trial and health economic evaluation of the impact of diagnostic testing for influenza, respiratory syncytial virus and Streptococcus pneumoniae infection on the management of acute admissions in the elderly and high-risk 18- to 64-year-olds

“…However, we did not stratify illness severity as part of the study or take into consideration the possibility that late treatment may benefit severely ill patients who are hospitalised with influenza, as such treatment falls outside NICE guidance. Evidence indicates that oseltamivir (Tamiflu ® , Roche) treatment of patients hospitalised with seasonal [71][72][73] and pandemic 2009 H1N1 influenza [74][75][76][77][78][79][80] is associated with reductions in radiological pneumonia, illness severity and death. Even when administered > 48 hours after symptom onset, oseltamivir showed considerable potential for reducing pneumonia due to 2009 pandemic H1N1 virus.…”

The characteristics, clinical manifestations and outcomes of pandemic influenza A (H1N1) 2009 in the elderly

“…Evolution of the disease is usually benign and self-limiting, and a reduction in symptoms usually occurs in an average of three days [7][8][9][10][11] . However, in the elderly, very young children, and individuals at high risk, with comorbidities or who are pregnant, the clinical symptoms of seasonal influenza can evolve to be serious 7,9,10,12 .…”