Asymptomatic Tuberculosis in the Namibia National Tuberculosis Prevalence Survey: Occurrence Under Various Case Definitions
6 affiliations
- 1School of Medicine University of Namibia Windhoek Namibia
- 2National Tuberculosis and Leprosy Programme Ministry of Health and Social Services Windhoek Namibia
- 3Department of Pulmonology, Allergology and Clinical Immunology Inselspital, Bern University Hospital, University of Bern Bern Switzerland
- 4World Health Organization Geneva Switzerland
- 5Amsterdam University Medical Centres University of Amsterdam Amsterdam the Netherlands
- 6Desmond Tutu TB Centre Stellenbosch University Stellenbosch South Africa
Abstract
Background: Asymptomatic tuberculosis (TB) is emerging as a disease state warranting attention because it is presumed infectious, yet affected individuals lack symptoms. The World Health Organization recommends screening for cough, fever, weight loss and night sweats and recently defined asymptomatic TB. However, the place of these symptoms in the definition has not yet been standardised. We determined the proportion of patients with bacteriologically confirmed asymptomatic TB without four symptom definitions: persistent cough (> 2 weeks), cough of any duration, W4SS of any duration or W4SS for > 2 weeks.
Methods: Secondary analysis of the Namibia TB prevalence survey data was performed; a representative sample had been interviewed for symptoms, underwent chest radiography and was offered bacteriological testing. The proportion of asymptomatic TB was computed for each definition. Logistic regression was used to determine factors associated with asymptomatic TB across four definitions.
Results: Among 29,495 participants in the nationally representative sample (86.8% of the target sample size), 123 TB cases met the case definition. Mean age was 45 years, and 74 (60%) were male. Of TB cases, 60/123 (48.8%) reported a cough of any duration, 20/123 (16.3%) a fever of any duration, 25/123 (20.3%) weight loss and 26/123 (21.1%) night sweats. Asymptomatic TB ranged from 39.8% to 63.0% by definition, with screening based on prolonged cough missing 63.0% of bacteriologically confirmed TB patients, while screening based on W4SS any duration missed 39.8% of TB cases.
Conclusion: Even when using an inclusive symptom screening system that includes any duration of the W4SS, asymptomatic TB occurred in 39.8%, highlighting a public health concern for asymptomatic TB. There is a need to standardise the symptoms being used when defining asymptomatic TB and we recommend the W4SS of any duration.
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BibTeX
@article{ruswa2026asymptomatic,
title = {{Asymptomatic Tuberculosis in the Namibia National Tuberculosis Prevalence Survey: Occurrence Under Various Case Definitions}},
author = {Nunurai Ruswa and Gunar Gunther and Farai Mavhunga and Frank Cobelens and Mareli Claassens},
journal = {Tropical Medicine \& International Health},
year = {2026},
month = jul,
doi = {10.1111/tmi.70206},
url = {https://doi.org/10.1111/tmi.70206},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Asymptomatic Tuberculosis in the Namibia National Tuberculosis Prevalence Survey: Occurrence Under Various Case Definitions
AU - Nunurai Ruswa
AU - Gunar Gunther
AU - Farai Mavhunga
AU - Frank Cobelens
AU - Mareli Claassens
PY - 2026
DA - 2026/07/28
JO - Tropical Medicine & International Health
DO - 10.1111/tmi.70206
UR - https://doi.org/10.1111/tmi.70206
AB - Background: Asymptomatic tuberculosis (TB) is emerging as a disease state warranting attention because it is presumed infectious, yet affected individuals lack symptoms. The World Health Organization recommends screening for cough, fever, weight loss and night sweats and recently defined asymptomatic TB. However, the place of these symptoms in the definition has not yet been standardised. We determined the proportion of patients with bacteriologically confirmed asymptomatic TB without four symptom definitions: persistent cough (> 2 weeks), cough of any duration, W4SS of any duration or W4SS for > 2 weeks. Methods: Secondary analysis of the Namibia TB prevalence survey data was performed; a representative sample had been interviewed for symptoms, underwent chest radiography and was offered bacteriological testing. The proportion of asymptomatic TB was computed for each definition. Logistic regression was used to determine factors associated with asymptomatic TB across four definitions. Results: Among 29,495 participants in the nationally representative sample (86.8% of the target sample size), 123 TB cases met the case definition. Mean age was 45 years, and 74 (60%) were male. Of TB cases, 60/123 (48.8%) reported a cough of any duration, 20/123 (16.3%) a fever of any duration, 25/123 (20.3%) weight loss and 26/123 (21.1%) night sweats. Asymptomatic TB ranged from 39.8% to 63.0% by definition, with screening based on prolonged cough missing 63.0% of bacteriologically confirmed TB patients, while screening based on W4SS any duration missed 39.8% of TB cases. Conclusion: Even when using an inclusive symptom screening system that includes any duration of the W4SS, asymptomatic TB occurred in 39.8%, highlighting a public health concern for asymptomatic TB. There is a need to standardise the symptoms being used when defining asymptomatic TB and we recommend the W4SS of any duration.
SN - 1360-2276
SN - 1365-3156
ER -