J Infect Dis 2019 Mar 29. Epub 2019 Mar 29.
Global Immunization Division, U.S. Centers for Disease Control and Prevention.
Background: Surveillance data from a large measles outbreak in Mongolia suggested an increased case fatality ratio (CFR) in the second of two waves. To confirm the increase in CFR and identify risk factors for measles death, we enhanced mortality ascertainment and conducted a case-control study among infants hospitalized for measles.
Methods: We linked national vital records with surveillance data of clinically- or laboratory-confirmed infant (aged <12 months) measles cases with rash onset during March-September 2015 (wave 1) and October 2015-June 2016 (wave 2). We abstracted medical charts of 95 fatal cases and 273 nonfatal cases hospitalized for measles, matched by age and sex. We calculated adjusted matched odds ratios (amORs) and 95% confidence intervals (CIs) for risk factors.
Results: Infant measles deaths increased from 3 among 2,224 cases (CFR: 0.13%) in wave 1 to 113 among 4,884 cases (CFR: 2.31%) in wave 2 (p<0.001). Inpatient admission, 7-21 days before measles rash onset, for pneumonia or influenza (amOR: 4.5; CI 2.6-8.0), but not other diagnoses, was significantly associated with death.
Discussion: Measles infection among children hospitalized with respiratory infections likely increased deaths due to measles during wave 2. Preventing measles virus nosocomial transmission likely decreases measles mortality.