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Etiological analysis of discarded measles in the context of a measles outbreak among a highly immunized population
Nuria Torner1,2, Sara Mercader3, Angela Dominguez1,2
1CIBER Epidemiology and Public Health CIBERESP, Institute Carlos III, Madrid, Spain.
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.
Insights
Accurate diagnosis of discarded measles cases is crucial for outbreak control, even in highly vaccinated populations. This study highlights the importance of molecular tools and serological testing for differential diagnosis.
Area of Science:
- Virology
- Epidemiology
- Immunology
Background:
- Measles poses significant global health risks, causing severe complications, morbidity, and mortality.
- Outbreaks can occur even in highly immunized populations, necessitating robust diagnostic strategies.
Purpose of the Study:
- To evaluate the etiological diagnosis of measles cases that were initially discarded during a measles outbreak.
- To assess the diagnostic utility of molecular and serological methods in a highly vaccinated setting.
Main Methods:
- A retrospective observational study of discarded measles cases during an outbreak in Catalonia (October 2006–July 2007).
- Case confirmation based on measles serum IgM, RT-PCR (urine/nasopharyngeal swab), or epidemiological linkage.
- Serological testing using commercial and in-house measles IgM enzyme immunoassays.
Main Results:
- Etiologies were determined for 11.2% of 89 discarded samples, including rubella, human herpesvirus 6, and measles.
- Significantly fewer confirmed measles cases (10%) were vaccinated compared to discarded cases (54%).
Conclusions:
- Sensitive surveillance systems are vital for measles case identification, outbreak response, and elimination efforts.
- Molecular and serological tools are essential for accurate differential diagnosis of suspected measles infections.
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