Research article
RNA viruses in community-acquired childhood pneumonia in semi-urban Nepal; a cross-sectional study
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* Corresponding author: Maria Mathisen maria.mathisen@cih.uib.no
1 Centre for International Health, University of Bergen, PO Box 7804, N-5020 Bergen, Norway
2 Medical Microbiology, Department of Laboratory Medicine, Sykehuset Innlandet Lillehammer, Norway
3 Department of Microbiology, Tribhuvan University Teaching Hospital, Kathmandu, Nepal
4 Child Health Department, Institute of Medicine, Tribhuvan University, Kathmandu, Nepal
5 Department of Epidemiology, Division of Epidemiology, Statens Serum Institut, Copenhagen, Denmark
6 Department of Microbiology and Infection Control, University Hospital of North Norway, Tromsø, Norway
7 Division of Infectious Disease Control, Norwegian Institute of Public Health, Oslo, Norway
BMC Medicine 2009, 7:35 doi:10.1186/1741-7015-7-35
Published: 27 July 2009Abstract
Background
Pneumonia is among the main causes of illness and death in children <5 years of age. There is a need to better describe the epidemiology of viral community-acquired pneumonia (CAP) in developing countries.
Methods
From July 2004 to June 2007, we examined nasopharyngeal aspirates (NPA) from 2,230 cases of pneumonia (World Health Organization criteria) in children 2 to 35 months old recruited in a randomized trial of zinc supplementation at a field clinic in Bhaktapur, Nepal. The specimens were examined for respiratory syncytial virus (RSV), influenza virus type A (InfA) and B (InfB), parainfluenza virus types 1, 2 and 3 (PIV1, PIV2, and PIV3), and human metapneumovirus (hMPV) using a multiplex reverse transcriptase polymerase chain reaction (PCR) assay.
Results
We identified 919 virus isolates in 887 (40.0%) of the 2,219 NPA specimens with a valid PCR result, of which 334 (15.1%) yielded RSV, 164 (7.4%) InfA, 129 (5.8%) PIV3, 98 (4.4%) PIV1, 93 (4.2%) hMPV, 84 (3.8%) InfB, and 17 (0.8%) PIV2. CAP occurred in an epidemic pattern with substantial temporal variation during the three years of study. The largest peaks of pneumonia occurrence coincided with peaks of RSV infection, which occurred in epidemics during the rainy season and in winter. The monthly number of RSV infections was positively correlated with relative humidity (rs = 0.40, P = 0.01), but not with temperature or rainfall. An hMPV epidemic occurred during one of the three winter seasons and the monthly number of hMPV cases was also associated with relative humidity (rs = 0.55, P = 0.0005).
Conclusion
Respiratory RNA viruses were detected from NPA in 40% of CAP cases in our study. The most commonly isolated viruses were RSV, InfA, and PIV3. RSV infections contributed substantially to the observed CAP epidemics. The occurrence of viral CAP in this community seemed to reflect more or less overlapping micro-epidemics with several respiratory viruses, highlighting the challenges of developing and implementing effective public health control measures.