Measles Outbreak in Kamukunji Sub-County, Nairobi County - Kenya, 2018
- Vaccine preventable diseases
Background:
In early 2018, measles outbreaks began in rural Kenya. In August 2018, cases were laboratory-confirmed in urban Kamukunji Sub-county, home to a large migrant, refugee population, with first-dose measles containing vaccine (MCV1) and second-dose measles containing vaccine (MCV2) coverage of 73% and 35% respectively in 2017. We conducted an epidemiologic investigation to inform control efforts.
Methods:
We reviewed health facility registers and interviewed community health workers regarding sick children residing near confirmed cases, including a boarding school. A suspected case was an illness with fever, maculopapular rash, and cough, coryza or conjunctivitis or one where a clinician suspected measles, in any person living or visiting Kamukunji during January 1–October 3, 2018. A confirmed case was measles immunoglobulin M (IgM) antibody positive, not induced by vaccination; epidemiologically linked to a laboratory-confirmed case without specimen; or clinically compatible without epi-linkage or adequate specimen collected. We interviewed cases or their guardians using a structured questionnaire. We collected serum samples for IgM antibody detection by enzyme-linked immunosorbent assay (ELISA) and nasopharyngeal samples for measles virus RNA detection by real-time polymerase chain reaction (RT-PCR) and genotyping by sequencing the detected virus. We calculated descriptive statistics and attack rates by various categories.
Results:
During January–October, 2018, we identified 67 confirmed cases [52 (78%) epi-linked and 15 (22%) laboratory- confirmed]; 28 (42%) from the community and 39 (58%) from health facilities. Of the confirmed cases, 43 (64%) were male; 39 (58%) were aged <5 years and 10 (15%) were aged <9 months (range: 3 months–19 years). The highest attack rate was 15 per 10,000 in children <1 year. Only 15 (28%) of 53 cases eligible for MCV1 had received it; and only nine (29%) of 31 cases eligible for MCV2 had received it. Of 16 blood samples collected, 10 (63%) were positive for measles IgM antibodies. Measles virus genotype B3 was detected in five (71%) of 7 nasopharyngeal samples collected.
Conclusion
This outbreak occurred among under-vaccinated children in an urban sub-county. Children aged <1 year had highest attack rates, illustrating the importance of providing two doses of MCV to eligible children in order to protect those most vulnerable.
In early 2018, measles outbreaks began in rural Kenya. In August 2018, cases were laboratory-confirmed in urban Kamukunji Sub-county, home to a large migrant, refugee population, with first-dose measles containing vaccine (MCV1) and second-dose measles containing vaccine (MCV2) coverage of 73% and 35% respectively in 2017. We conducted an epidemiologic investigation to inform control efforts.
Methods:
We reviewed health facility registers and interviewed community health workers regarding sick children residing near confirmed cases, including a boarding school. A suspected case was an illness with fever, maculopapular rash, and cough, coryza or conjunctivitis or one where a clinician suspected measles, in any person living or visiting Kamukunji during January 1–October 3, 2018. A confirmed case was measles immunoglobulin M (IgM) antibody positive, not induced by vaccination; epidemiologically linked to a laboratory-confirmed case without specimen; or clinically compatible without epi-linkage or adequate specimen collected. We interviewed cases or their guardians using a structured questionnaire. We collected serum samples for IgM antibody detection by enzyme-linked immunosorbent assay (ELISA) and nasopharyngeal samples for measles virus RNA detection by real-time polymerase chain reaction (RT-PCR) and genotyping by sequencing the detected virus. We calculated descriptive statistics and attack rates by various categories.
Results:
During January–October, 2018, we identified 67 confirmed cases [52 (78%) epi-linked and 15 (22%) laboratory- confirmed]; 28 (42%) from the community and 39 (58%) from health facilities. Of the confirmed cases, 43 (64%) were male; 39 (58%) were aged <5 years and 10 (15%) were aged <9 months (range: 3 months–19 years). The highest attack rate was 15 per 10,000 in children <1 year. Only 15 (28%) of 53 cases eligible for MCV1 had received it; and only nine (29%) of 31 cases eligible for MCV2 had received it. Of 16 blood samples collected, 10 (63%) were positive for measles IgM antibodies. Measles virus genotype B3 was detected in five (71%) of 7 nasopharyngeal samples collected.
Conclusion
This outbreak occurred among under-vaccinated children in an urban sub-county. Children aged <1 year had highest attack rates, illustrating the importance of providing two doses of MCV to eligible children in order to protect those most vulnerable.