Surveillance of Influenza Infections among a Cohort of Adult Factory Workers in Bandung, Indonesia

Session I – Kosasih, Herman

Title of Contribution: Surveillance of Influenza Infections among a Cohort of Adult Factory Workers in Bandung, Indonesia
Author(s): Ardini Raksanagara1, Nugroho Susanto2, Chairin Ma'roef2, Ungke Antonjaya2, Rismalia2, Gustiani2, Hadidjah Chrisno1, Herman Kosasih2, Timothy H. Burgess3, Patrick J Blair4, and Maya Williams2
Affiliation(s): 1 PT Grandtex, Bandung, Indonesia , 2 Naval Medical Research Unit Two, Jakarta, Indonesia, , 3 Naval Medical Research Center, Silver Spring, Maryland, 4Naval Health Research Center, San Diego, California

Abstract:
To determine the disease burden and clinical manifestations associated with influenza infections in an adult population, influenza-like illness (ILI) surveillance was conducted at a factory in Bandung, Indonesia from September 2004 until April 2008.  The factory is comprised of approximately 1,800 adult workers, and as employees have to provide a medical certificate from the factory clinic when they are absent from work, most employees did not seek medical assistance elsewhere. Workers enrolled in ILI surveillance had to have a body temperature >37 C accompanied by at least one of the following symptoms: coryza, cough or sore throat. During forty four months of observation, 1408 patients were enrolled in the surveillance program. Influenza infections were confirmed in 429 (30.5%) cases, consisting of 135 (9.6%) influenza A H1N1, 202 (14.3%) influenza A H3N2, and 89 (6.3%) influenza B. This percentage of confirmed influenza infections is significantly (p<0.01) higher than the overall national program percentage (30.5% vs 22%). Although influenza cases were identified all year round, the majority of cases were identified during the rainy season (approximately 77.2%). During this season, influenza A was predominant (90%), while during the dry season influenza B was predominant (56%). The clustering of cases among employees occurred quite frequently (19 clusters/per year).  Clinically, in confirmed influenza cases, cough, coryza and anorexia were significantly (p<0.01) more frequent than non-confirmed cases.  Additionally, confirmed influenza infections caused significantly (p<0.01) longer absenteeism than non-influenza cases (1.55 days vs 1.25 days).  The incidence rate of influenza among employees was 62/1000 employees per year. Direct cost (medical and absenteeism cost) for the factory due to influenza was US$ 364.86/1000 employees year. This surveillance provides valuable information related to the disease burden of influenza in adults and should be extended to evaluate the efficacy and cost/benefit of influenza vaccination among adult workers.