Etiological analysis of discarded measles in the context of a measles outbreak among a highly immunized population

Abstract

Background Measles can lead to serious complications and remains an important cause of morbidity and mortality worldwide. In this study we aimed to assess the etiological diagnosis of discarded measles cases in the context of an outbreak among a highly immunized population. Methods We conducted a retrospective observational study of discarded measles cases from an outbreak that occurred from October 2006 to July 2007 in Catalonia. A confirmed case was defined as having a positive measles serum IgM result and/or a positive result by RT‐PCR in urine and/or nasopharyngeal swab; or an epidemiological link to a confirmed case. Serum specimens were tested by a commercially available indirect‐format and by an in‐house capture‐format measles IgM enzyme immunoassays. Results Testing of 89 samples discarded for measles determined the etiologies for 10 (11.2%), including one rubella, three human herpes virus 6, and six measles infections. Of 381 confirmed cases in the outbreak, 10% had received at least one dose of the measles‐mumps‐rubella vaccine versus 54% of the discarded for measles (OR: 0.09; 95% CI: 0.06, 0.14; p < 0.001). Conclusions Highly sensitive surveillance systems are critical to identifying cases, responding to outbreaks and verifying progress towards measles elimination. Molecular tools for measles detection and differential diagnosis, and collection of appropriate specimens for molecular and serological testing are essential to correctly diagnose suspected measles infection.

Differential diagnosis of fever and rash cases negative for measles and rubella to complement surveillance activities

“…Differential diagnosis allowed us to reduce the number of undiagnosed cases from 32% to 12% (including 21 cases untested due to sample unavailability), corresponding to an overall percentage of viral identification of 88%. This percentage is higher compared with other studies performing fever and rash differential diagnosis (e.g., 52.7% in a study conducted in Belarus, 20 11.2% in a study conducted in Catalonia, 18 and 16.1% in Cuba 32 ). However, the number of investigated pathogens was higher in our study, and this may explain some of these differences.…”

“…Moreover, these studies were conducted in countries close to measles and rubella elimination 19,20 or that already achieved the elimination goal. 18,32 To the best of our knowledge, our study is the first to extend fever and rash differential diagnosis to 10 pathogens using molecular methods. With molecular screening, we identified at least one pathogen in 65% of the tested samples.…”

“…However, the number of investigated pathogens was higher in our study, and this may explain some of these differences. Moreover, these studies were conducted in countries close to measles and rubella elimination 19,20 or that already achieved the elimination goal 18,32 …”

“…The spectrum of viral causes of exanthems includes human herpesviruses, parvovirus, enteroviruses (EV), adenoviruses, and SARS‐CoV‐2 15–17 . However, there is a lack of studies that explore the presence of other pathogens associated with morbilliform rash in measles and rubella discarded cases, 18–21 and consequently, little information about the epidemiological characteristics and the burden of each pathogen is available. The aim of this study was to investigate biological samples collected from discarded cases over the years of surveillance activities in Lombardy (2017−2022) to identify other viral pathogens implicated in morbilliform manifestations and improve surveillance activities.…”

“…15 The spectrum of viral causes of exanthems includes human herpesviruses, parvovirus, enteroviruses (EV), adenoviruses, and SARS-CoV-2. [15][16][17] However, there is a lack of studies that explore the presence of other pathogens associated with morbilliform rash in measles and rubella discarded cases, [18][19][20][21] and consequently, little information about the epidemiological characteristics and the burden of each pathogen is available.…”