Abstract
Following the indication of the World Health Organization, a national plan for the elimination of measles was approved in Italy and this included the improvement of the molecular surveillance of measles viruses and the interruption of indigenous transmission of the disease. Nevertheless, large outbreaks continue to occur in almost all regions of the country, including Sicily. Here we describe the epidemiology and molecular dynamics of measles viruses as a result of the measles surveillance activity carried out by the “Reference Laboratory for Measles and Rubella” in Sicily over a 5-year period. Biological samples of 259 suspected measles cases were tested for viral RNA detection and a total of 223 (86.1%) were classified as laboratory confirmed. The median age of confirmed measles cases was 21.0 years and about half of them were adults aged 19 years and older. Overall, one-third of the patients showed clinical complications and these latter were more common among adults than children (44.9% vs. 25.7%). The vast majority of measles cases were unvaccinated (94.2%, n = 210). The phylogenetic analysis of 221 measles virus nucleotide sequences revealed sporadic detections of genotypes D4 and H1, while endemic circulation of genotypes D8 and B3 was documented. Genotype D8 was associated with epidemics occurred between 2013 and 2016, whereas genotype B3 was more recently introduced into Sicily characterizing the current measles outbreak. The results of this study confirm the autochthonous co-circulation of viral variants belonging to different genotypes during the study period, and emphasizes the need of measles surveillance programmes in order to investigate the viral dynamics, the pathways of disease transmission, and to eventually adapt the development of successfull vaccine formulations.
Highlights
Measles is a highly contagious human disease characterized by acute symptoms including high fever, conjunctivitis, coryza, cough and a maculopapular rash
Local Health Authority (LHA) is responsible for the investigation and public health management of suspected cases and contacts, following the case definition of the European Union (EU) Commission Decision of 2012 [5]
This study aimed to report the epidemiology of measles infection in Sicily, describing the genetic diversity of circulating measles virus (MV) and variants during the period 2012–2017 by using a phylogenetic approach
Summary
Measles is a highly contagious human disease characterized by acute symptoms including high fever, conjunctivitis, coryza, cough and a maculopapular rash. The World Health Organization (WHO) have launched a global strategic plan with the goal of improving the implementation of vaccination programmes for measles and rubella elimination [1]. This determined the interruption of transmission in the WHO region of the Americas [2], whereas the Eastern Mediterranean, European and Western Pacific WHO regions have formally set target dates for measles elimination [3]. Despite efforts and recommendations of the public health community, sustained outbreaks continue to occur in countries which introduced mass vaccination schedules against measles, as part of their national immunization programmes, and an estimated 134,200 global deaths for measles were reported in 2015, mostly in low-income countries [4]. Molecular data are used to recognize authocthonous or imported cases and to identify epidemiologically-linked outbreaks
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