Factors contributing to measles transmission during an outbreak in Kamwenge District Western Uganda April to August 2015.

Friday, 12th of January 2018

BMC Infect Dis. 2018 Jan 8;18(1):21. doi: 10.1186/s12879-017-2941-4.

Factors contributing to measles transmission during an outbreak in Kamwenge District Western Uganda April to August 2015.

Nsubuga F¹ Bulage L² Ampeire I³ Matovu JKB⁴ Kasasa S⁴ Tanifum P⁵ Riolexus AA² Zhu BP⁵.

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Abstract

BACKGROUND:

In April 2015 Kamwenge District western Uganda reported a measles outbreak. We investigated the outbreak to identify potential exposures that facilitated measles transmission assess vaccine effectiveness (VE) and vaccination coverage (VC) and recommend prevention and control measures.

METHODS:

For this investigation a probable case was defined as onset of fever and generalized maculopapular rash plus ≥1 of the following symptoms: Coryza conjunctivitis or cough. A confirmed case was defined as a probable case plus identification of measles-specific IgM in serum. For case-finding we reviewed patients medical records and conducted in-home patient examination. In a case-control study we compared exposures of case-patients and controls matched by age and village of residence. For children aged 9 m-5y we estimated VC using the percent of children among the controls who had been vaccinated against measles and calculated VE using the formula VE = 1 - OR_M-H where OR_M-H was the Mantel-Haenszel odds ratio associated with having a measles vaccination history.

RESULTS:

We identified 213 probable cases with onset between April and August 2015. Of 23 blood specimens collected 78% were positive for measles-specific IgM. Measles attack rate was highest in the youngest age-group 0-5y (13/10000) and decreased as age increased. The epidemic curve indicated sustained propagation in the community. Of the 50 case-patients and 200 controls 42% of case-patients and 12% of controls visited health centers during their likely exposure period (OR_M-H = 6.1; 95% CI = 2.7-14). Among children aged 9 m-5y VE was estimated at 70% (95% CI: 24-88%) and VC at 75% (95% CI: 67-83%). Excessive crowding was observed at all health centers; no patient triage-system existed.

CONCLUSIONS:

The spread of measles during this outbreak was facilitated by patient mixing at crowded health centers suboptimal VE and inadequate VC. We recommended emergency immunization campaign targeting children <5y in the affected sub-counties as well as triaging and isolation of febrile or rash patients visiting health centers.