Epidemiological and molecular investigation of a measles outbreak in Punjab, Pakistan, 2013‐2015

Abstract

Despite the availability of an effective vaccine, the measles virus continues to cause significant morbidity and mortality in children worldwide. Molecular characterization of wild-type measles strains is an invaluable component of epidemiological studies or surveillance systems that provides important information pertinent to outbreak linkages and transmission pathways. Serum samples and throat swabs were collected from suspected measles cases from the Punjab province of Pakistan (2013-2015) and further tested for measles immunoglobulin M (IgM) through enzyme-linked immunosorbent assay and reverse-transcriptase polymerase chain reaction for molecular characterization. Among the total of 5415 blood samples, 59% tested positive for measles IgM. Males had a higher infection rate (55%) than females (45%), and the highest frequency of positive cases (63%) was found in the age group of 0 to 5 years. Partial sequencing of the nucleoprotein gene showed that 27 strains belonged to the B3 genotype, whereas 2 viruses were identified as D4. On phylogenetic analysis, Pakistani B3 strains were found to be closely related to previously reported indigenous strains and those from neighboring countries of Iran and Qatar. This is the first report on the detection of the measles B3 genotype from Punjab, Pakistan. The current study shows a high burden of measles infections in Punjab province owing to poor routine immunization coverage in major cities. It is imperative that national health authorities adopt strategic steps on an urgent basis for improvement of routine immunization coverage. Molecular epidemiology of the measles viruses circulating in different parts of the country can provide useful data to manage future outbreaks.

Measles and Rubella Incidence and Molecular Epidemiology in Senegal: Temporal and Regional Trends during Twelve Years of National Surveillance, 2010–2021

“…Our reported male–female ratio of 1:1.2 in IgM-positive measles cases is consistent with findings from Zaidi et al [ 32 ], and disproportionate to the child (<7years) sex ratio of 1:1.06 in Senegal ( , accessed on 1 August 2022). The even higher male–female ratio of suspected cases of 1:1.4 may suggest a difference in care-seeking or other factors influencing case-finding, as sex-related differences in measles incidence are not consistently reported elsewhere [ 34 , 35 ].…”

“…Consistent with other studies in Burkina Faso, Italy and Pakistan [ 30 , 31 , 32 ], the majority of both measles (96.9%) and rubella (77.9%) infections were in unvaccinated patients (or those with unknown vaccination status). The type of vaccine (i.e., MCV vs. MRV), however, is not captured in our data—and so inferences cannot be made regarding rubella vaccine failure, although very few rubella cases occurred in children with a documented vaccine history following MRV introduction in 2014.…”

“…Our phylogenetic analyses supported evidence from one previous study [ 17 ] that there is exclusive circulation of the B3 measles genotype in Senegal, as in several other sub-Saharan African [ 39 , 40 ], European [ 7 , 31 , 41 , 42 ] and Asian [ 32 ] countries. This differs to some settings in Europe, including France Italy and Romania where co-circulation of genotypes D8 and B3 have been detected [ 7 , 43 , 44 ].…”

“…Most confirmed measles infections were in children less than five years of age (55.8%), suggesting coverage within the EPI may still be insufficient. Conversely, rubella cases were more commonly reported in the 5–15 years age group, in line with findings in Pakistan and Cameroon, where 63% and 97% of laboratory confirmed cases belonged to this age group, respectively, suggesting the need for additional catch-up immunization [ 29 , 32 ]. This is of particular concern given that 21.5% of women in Senegal give birth before the age of 18 (32.4% in rural districts), heightening the risk of congenital rubella as a complication in this age group [ 33 ].…”

“…This differs to some settings in Europe, including France Italy and Romania where co-circulation of genotypes D8 and B3 have been detected [ 7 , 43 , 44 ]. All B3 strains detected in the current study clustered into a B3.1 sub-genotype—previously detected in Cameroon, Central African Republic, Ghana, Nigeria, Kenya, Tanzania and Pakistan [ 32 , 40 , 45 , 46 , 47 ]. However, the B3.3 lineage previously reported to be the dominant circulating sub-genotype in the period 2009–2011 in Senegal [ 17 ] was not detected in the present study, possibly due to a non-exhaustive sequencing.…”