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Abstract
Objectives To estimate the impact of a smallpox attack in Mumbai, India, examine the impact of case isolation and ring vaccination for epidemic containment and test the health system capacity under different scenarios with available interventions.
Setting The research is based on Mumbai, India population.
Interventions We tested 50%, 70%, 90% of case isolation and contacts traced and vaccinated (ring vaccination) in the susceptible, exposed, infected, recovered model and varied the start of intervention between 20, 30 and 40 days after the initial attack.
Primary and secondary outcome measures We estimated and incorporated in the model the effect of past vaccination protection, age-specific immunosuppression and contact rates and Mumbai population age structure in modelling disease morbidity and transmission.
Results The estimated duration of an outbreak ranged from 127 days to 8 years under different scenarios, and the number of vaccine doses needed for ring vaccination ranged from 16 813 to 8 722 400 in the best-case and worst-case scenarios, respectively. In the worst-case scenario, the available hospital beds in Mumbai would be exceeded. The impact of a smallpox epidemic may be severe in Mumbai, especially compared with high-income settings, but can be reduced with early diagnosis and rapid response, high rates of case finding and isolation and ring vaccination.
Conclusions This study tells us that if smallpox re-emergence occurs, it may have significant health and economic impact, the extent of which will depend on the availability and delivery of interventions such as a vaccine or antiviral agent, and the capacity of case isolation and treatment. Further research on health systems requirements and capacity across the diverse states and territories of India could improve the preparedness and management strategies in the event of re-emergent smallpox or other serious emerging infections.
- public health
- infection control
- virology
- smallpox
- variola
- vaccines
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Footnotes
Contributors CRM designed the study and developed the research questions, supervised the research, drafted and revised the manuscript, gave final approval of the manuscript. VC participated in the literature review and study development, developed research questions, modelling analysis and drafted and revised the manuscript. BM conducted a literature review, collected the data, performed modelling analysis and drafted and revised the manuscript. AAC helped with the development of the study, participated in the literature review and manuscript drafting and revision. JN participated in the literature review, study development, drafted and revised the manuscript. AD collected the data, participated in the literature review and drafted the manuscript.
Funding Raina MacIntyre is supported by a NHMRC Principal Research Fellowship, grant number 1137582.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplemental information. All data used in this study are publicly available online and listed in the references.
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