Epidemiology and Infection



Seasonal trends of viral respiratory tract infections in the tropics


F. T. CHEW a1, S. DORAISINGHAM a2, A. E. LING a2, G. KUMARASINGHE a3 and B. W. LEE a1c1
a1 Department of Paediatrics, National University of Singapore
a2 Department of Pathology, Singapore General Hospital
a3 Department of Microbiology, National University Hospital, Singapore

Abstract

To evaluate the seasonal trends of viral respiratory tract infections in a tropical environment, a retrospective survey of laboratory virus isolation, serology and immunofluorescence microscopy in two large general hospitals in Singapore between September 1990 and September 1994 was carried out. Respiratory tract viral outbreaks, particularly among infants who required hospitalization, were found to be associated mainly with respiratory syncytial (RSV) infections (72%), influenza (11%) and parainfluenza viruses (11%). Consistent seasonal variations in viral infections were observed only with RSV (March–August) and influenza A virus (peaks in June, December–January). The RSV trends were associated with higher environmental temperature, lower relative humidity and higher maximal day-to-day temperature variation. Although the influenza A outbreaks were not associated with meteorological factors, influenza B isolates were positively associated with rainfall. These data support the existence of seasonal trends of viral respiratory tract infections in the tropics.

(Accepted January 1 1998)


Correspondence:
c1 Author for correspondence: Dr B. W. Lee, Department of Paediatrics, National University of Singapore, Lower Kent Ridge Road, Singapore 119074.


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