Do seasonal patterns of influenza virus and respiratory syncytial virus correlate with pneumococcal disease in rural Thailand?
Session IV – Rhodes, Julia
Title of Contribution: Do seasonal patterns of influenza virus and respiratory syncytial virus correlate with pneumococcal disease in rural Thailand?
Author(s): Julia Rhodes PhD,1 Henry Baggett MD,MPH, 1 Malinee Chittaganpitch MSc, 2 Sathapana Naorat MSc, 1 Prabda Prapasiri PhD, 1 Mark Simmerman PhD, RN, 1 Surang Dejsirilert MSc,2 Somrak Chantra MD,3 Pongpun Sawatwong, MSc,1 Dean Erdman, DrPH,4 Matthew R. Moore MD, MPH, 4 Sonja J. Olsen PhD, 4 Leonard Peruski PhD, 1 Kumnuan Ungchusak MD, MPH,5 Susan A. Maloney MD, MHSc1
Affiliation(s): 1International Emerging Infections Program, Thailand Ministry of Public Health (MOPH) – U.S. Centers for Disease Control and Prevention (CDC) Collaboration, Nonthaburi, Thailand, 2National Institute of Health, MOPH, Nonthaburi, Thailand, 3Sa Kaeo Provincial Health Office, MOPH, Sa Kaeo, Thailand, 4CDC, Atlanta, GA, 5Bureau of Epidemiology, MOPH, Nonthaburi, Thailand
Background: In temperate climates, seasonal peaks of influenza virus (flu) and respiratory syncytial virus (RSV) occur each winter and coincide with peaks in invasive pneumococcal disease (IPD). This together with findings from animal models, suggest that flu and RSV infections may predispose patients to IPD. We examined disease patterns in Thailand, a tropical climate where flu and RSV tend to peak during June through October.
Methods: We initiated active, population-based surveillance for patients hospitalized with pneumonia in 2 rural Thailand provinces in 2003. Clinical pneumonia was defined as evidence of acute infection with signs or symptoms of respiratory disease. A sample of pneumonia patients with chest radiographs performed within 48 hours of admission provided nasopharyngeal swabs for flu and RSV testing by PCR. In these same provinces enhanced surveillance for bacteremia requiring hospitalization, including S. pneumoniae bacteremia (SPN), began in November 2005. We compared SPN case counts during months of peak flu and RSV activity to SPN counts during the non-peak months for flu and RSV.
Results: From Nov 2005-Dec 2007, we identified 429 flu and 385 RSV pneumonia cases. In 2006, flu and RSV positivity rates peaked during June-Oct and corresponded with a non-significant increase in SPN: 9.2 cases/month from June-Oct vs 6.4 for the rest of 2006 (p=0.38) (Figure). In 2007 RSV positivity again peaked from June-Oct with no corresponding increase in SPN: 2.4 (June-Oct) vs. 6.0 (Nov-May) cases/month, p=0.05. In contrast, in 2007 flu positivity peaked in Feb and March, with a smaller increase around November. This shift of the flu peak to Feb-Mar corresponded to a non-significant increase in SPN: 7.5 (Feb-Mar) vs. 3.9 (remainder of 2007) cases/month, p=0.15. Overall from Nov 05-Dec 07 monthly SPN cases were not statistically correlated with monthly positivity rates of flu (R2=.13, p=0.52) or RSV (R2=.13, p=0.52) Results were unchanged when SPN cases were limited to patients with pneumonia.
Conclusions: Seasonal peaks in flu and RSV do not appear to correlate with increases in SPN in these two provinces in rural Thailand. As data from tropical regions are scarce, these findings contribute to ongoing discussions about potential associations between flu, RSV and pneumococcal disease.
