Investigation of a Measles Outbreak in Kasumbalesa, Chililabombwe District – Zambia 2021.
- Healthcare related infections
Background
Zambia still experiences annual measles outbreaks despite having made major strides toward its control. On 15 November 2021, Chililabombwe district reported 24 cases of acute febrile rash illness and 3 deaths that occurred in Kasumbalesa border town.
Methods
We conducted an outbreak investigation in Kasumbalesa Township from 17-23 November 2021. A case-control study was done using a structured questionnaire to identify risk factors for cases of acute febrile rash illness. A case was defined as anyone who presented with acute febrile rash illness from August 2021 and controls were derived from the cases households and selected households. Twenty-four serology and fifteen genomic sequencing samples were collected from suspected cases for laboratory analysis. We used logistic regression to calculate adjusted odds ratios and 95% Confidence intervals.
Results
420 people were elicited of which 33 were cases while 387 were controls. There were 3 deaths among cases. Median ages for cases and controls were 38 and 25 years (ranges 0.5–95 and 1–82) respectively, 60% of the cases were female. 2 (7%) of the cases and 303 (81%) of the controls were either fully or partially vaccinated against measles. Eighteen of the 24 samples tested positive for measles IgM and 6 of 15 samples had identical sequences recovered and contained a viral strain, genotype B3. Major predictors for measles infection were being unvaccinated [AOR 46.6, 95%CI: 10.2- 363.0], household religious affiliation (Zionist religious sect) [AOR 100.7 (95%CI 25.2 - 606.6)], age [AOR 0.9, 95%CI: 0.8 – 1.0] and sex - males [AOR 0.2, 95%CI: 0.0 – 0.8].
Conclusion
Religious affiliation is a key factor in vaccine hesitancy seen among some religious communities. This leads to low vaccine coverage and increased risk of measles outbreaks. Health messaging should target health promotion, disease prevention and treatment including behavioural change in high risk communities.
Zambia still experiences annual measles outbreaks despite having made major strides toward its control. On 15 November 2021, Chililabombwe district reported 24 cases of acute febrile rash illness and 3 deaths that occurred in Kasumbalesa border town.
Methods
We conducted an outbreak investigation in Kasumbalesa Township from 17-23 November 2021. A case-control study was done using a structured questionnaire to identify risk factors for cases of acute febrile rash illness. A case was defined as anyone who presented with acute febrile rash illness from August 2021 and controls were derived from the cases households and selected households. Twenty-four serology and fifteen genomic sequencing samples were collected from suspected cases for laboratory analysis. We used logistic regression to calculate adjusted odds ratios and 95% Confidence intervals.
Results
420 people were elicited of which 33 were cases while 387 were controls. There were 3 deaths among cases. Median ages for cases and controls were 38 and 25 years (ranges 0.5–95 and 1–82) respectively, 60% of the cases were female. 2 (7%) of the cases and 303 (81%) of the controls were either fully or partially vaccinated against measles. Eighteen of the 24 samples tested positive for measles IgM and 6 of 15 samples had identical sequences recovered and contained a viral strain, genotype B3. Major predictors for measles infection were being unvaccinated [AOR 46.6, 95%CI: 10.2- 363.0], household religious affiliation (Zionist religious sect) [AOR 100.7 (95%CI 25.2 - 606.6)], age [AOR 0.9, 95%CI: 0.8 – 1.0] and sex - males [AOR 0.2, 95%CI: 0.0 – 0.8].
Conclusion
Religious affiliation is a key factor in vaccine hesitancy seen among some religious communities. This leads to low vaccine coverage and increased risk of measles outbreaks. Health messaging should target health promotion, disease prevention and treatment including behavioural change in high risk communities.