Measles is a highly contagious viral disease that spreads through aerosolized respiratory droplets or contact with nasal and throat secretions of infected individuals¹. Clinically, it presents with fever, maculopapular rash, malaise, cough, coryza, and conjunctivitis. The virus has a secondary attack rate of over 90% among susceptible individuals, with infected persons being contagious from 4 days before to 4 days after the onset of the rash, which typically spreads from the face to the trunk and lower extremities².Measles is typically a mild to moderately severe illness but poses a higher risk of complications in children under 5 years and adults over 30, especially in malnourished children, those with vitamin A deficiency, or weakened immune systems due to HIV or other conditions³. The disease weakens the immune system and can impair the body’s ability to defend against infections. Common complications include otitis media, laryngo-tracheobronchitis, pneumonia, transient cellular immunity suppression, severe diarrhea with dehydration, and encephalitis⁴. Measles remains endemic in developing countries due to low immunization coverage, despite humans being the only reservoir and the absence of subclinical cases. Its highly effective vaccine makes measles a strong candidate for eradication; however, elimination has only been achieved in a few regions globally, primarily due to social and political challenges and the disease's high transmissibility.Measles poses a significant threat to children from economically weaker backgrounds, particularly those who are malnourished, unimmunized, partially immunized, or have weakened immunity⁵. Despite the availability of a safe and effective vaccine since the 1960s, measles and rubella remain major public health concerns in India. The vaccine not only protects children from severe illnesses but also helps interrupt disease transmission within communities⁶.

AIM

To confirm the clinically suspected cases and genotyping of Measles virus

The present study was a laboratory-based, descriptive observational study conducted at the WHO National Measles Laboratory, Department of Microbiology, SMS Medical College, Jaipur, Rajasthan, from January 2023 to December 2023, following approval from the research review board and ethical committee. The study included 230 serum, urine, and throat swab samples collected from clinically suspected cases of measles received at the laboratory. Data collection was carried out using a laboratory requisition form, which recorded information such as age, sex, geographical area, vaccination status, and relevant clinical history of the patients.  Investigation techniques included ELISA for IgM antibody detection and conventional RT-PCR for viral RNA detection and genotype identification.  Eligibility criteria were based on the WHO measles case definition, which identifies a measles case as "any person with a generalized maculopapular rash lasting three or more days, with a body temperature of 38.3°C (101°F) or higher, and cough, coryza, or conjunctivitis." Only specimens with proper labeling and completed requisition forms, including patient details (e.g., name, age, sample collection date, date of rash onset, EPID number, and district), were included. Blood was collected in plain vials, or separated serum in vials without anticoagulants, and transported under appropriate cold-chain conditions.  Exclusion criteria included mismatched identification on requisition forms and specimens, insufficient sample quantity (less than 0.5 µL), unlabelled or mislabelled specimens, failure to maintain the cold chain during transportation, and any sample that posed a health or safety hazard to laboratory personnel (e.g., leaking samples).

Table 1. Association of Measles with Age

The study shows a significant association between age and measles prevalence (X² = 13.63, p = 0.019), with the highest cases observed in the 1-5 year age group, indicating higher susceptibility in younger age groups.

Table 2. Association of Measles with Gender

The above table shows, In females, 1 case was equivocal, 51 were negative, and 29 were positive. And in males, 91 were negative, and 58 were positive with no equivocal cases. The P value 0.36 indicates no significant association between gender and Measles status.

Table 3: Association of Measles with Vaccination status

Table shows a significant association between vaccination status and measles prevalence (X² = 70.34, p = 0.0001), with higher positivity among unvaccinated and unknown status individuals compared to vaccinated ones.

Table 4. Measles Status of Subjects by ELISA (n=230)

This table shows that out of 230, 61.7% (142/230) tests negative for Measles and 37.8% (87/230) tested positive for Measles and a very small percentage 0.4% (1/230) showed an Equivocal result.

Table 5. RT-PCR Reports for Measles (n=87)

The above table shows out of 87 serologically positive samples, 94.25% (82/87) were positive for Measles by RT-PCR, and 5.25% (5/87) were negative

Table 6. Measles Genotype (n=82)

 Table shows in our study all genotypes belonged to D8 (100%) only.

Graph . District Wise Distribution of Measles Cases (n=230)

Jodhpur district shown highest Measles positive cases 26.4% (23/42), while Sikar, Sirohi, Udaipur, Chittorgarh, Ganganagar, Hanumangarh dose not show any case.

The results of this study provide comprehensive insights into the demographic, epidemiological, and virological patterns of Measles  in the population under study.

The age distribution shows a clear pattern of disease susceptibility, with children in the 1-5 year age group making up the largest proportion of cases 53%. This finding aligns with global patterns where young children, especially those under 5 years old, are more vulnerable to Measles due to their developing immune systems and higher likelihood of inadequate vaccination coverage. Infants under 1 year of age account for 12.2% of cases, reinforcing the critical need for maternal immunity and timely vaccination.

Interestingly, the prevalence of Measles decreases as age increases. The 6-10 year age group constitutes 17% of the sample, and it further drops to 8.3% in the 11-15 year group, and only 5% in the 16-18 year group. The decline in cases among older age groups could be attributed to both higher vaccination coverage in later childhood and the natural development of immunity over time. It is notable that the 18 yrs above age group accounts for only 4.8% of cases, reflecting the effective role of vaccination programs in earlier years. Syed TA et al (2015)⁷ also showed the highest number of positive cases was in the 1-5 years age group.

A gender disparity is observed, with a higher prevalence of Measles among males 64.8% compared to females 35.2%. While the reasons for this difference are not immediately clear, it could be due to a variety of social and biological factors. In many regions, male children are more likely to receive healthcare services earlier, which may account for more diagnosed cases. However, the absence of a statistically significant association between gender and Measles status, as indicated by a p-value of 0.36, suggests that gender may not play a strong role in disease susceptibility. Kamaljit Singh et al (2017)⁸ in Rajasthan studied 23 suspected Measles outbreaks, majority i.e. 14 (60.8%) were found to be of Measles.

The vaccination status of subjects highlights a key public health challenge. While 51% of the population is vaccinated, 29% have not been vaccinated, and 12% have unknown vaccination histories. This leaves a significant portion of the population susceptible to Measles outbreaks. The relatively low vaccination coverage, which is suboptimal from a public health perspective, could contribute to the continued transmission of the disease.

The association between vaccination status and Measles infection is striking, with a chi square value of 70.34 and a p-value of 0.0001, indicating a highly significant association. Among vaccinated individuals, only 14 cases of Measles were reported, while 41 cases were found among unvaccinated individuals. This demonstrates the effectiveness of the Measles vaccine in preventing infection, as those who were vaccinated were far less likely to contract the disease.

Benjamin KCW et al (2019)⁹ studied a mass second-dose Measles immunization campaign’s (implemented in 2010) impact on Measles mortality using the nationally representative Million Death Study (including 27,000 child deaths in 1.3 million households surveyed from 2005 to 2013). 1-59 month Measles mortality rates fell more in the campaign states following launch 27% versus non-campaign states 11%. Declines were steeper in girls than boys and were specific to Measles deaths. Measles mortality risk was lower for children living in a campaign district (OR 0.6, 99% CI 0.40.8) or born in 2009 or later (OR 0.8, 99% CI 0.7-0.9). The campaign averted up to 41,000-56,000 deaths during 2010-13, or 39-57% of the expected deaths nationally. Elimination of Measles deaths in India is feasible.

The serological analysis reveals that 61.7% of subjects tested negative for Measles, while 37.8% tested positive. Only a small proportion 0.4% yielded an equivocal result, indicating the need for confirmatory tests in such cases. When confirmed with RT-PCR, 94.25% of seropositive samples tested positive for Measles, underscoring the sensitivity and reliability of RT-PCR as a diagnostic tool in this context. Jallow, M.M .et al [2022]¹⁰ found among 8082 laboratory tested specimens from Measles suspected cases, serological evidence of Measles  infection was confirmed in 1303/8082 (16.1%). The incidence of  Measles progress towards pre-elimination targets (<1.0 case per million people per year) appears to have stalled; there were 10.8 (95% CI 9.3-12.5) cases per million people in 2021.

Genotypic analysis shows that the D8 genotype was present in 100% of the Measles cases. This finding is significant as the D8 genotype is known to be one of the predominant circulating genotypes in many regions. The exclusive presence of this genotype in the study population suggests a potential outbreak from a common source or limited genetic diversity of circulating Measles strains in the region. Similarly Akhalesh K Shakya et al (2012)¹¹  in their study found that Genetic analysis of circulating Measles strains (n = 38) in Uttar Pradesh from 235 cases of laboratory confirmed cases out of 526 suspected Measles cases between 2008 and 2011 showed that all viruses responsible for outbreaks were within clade D and all were genotype D8.

The district-wise distribution highlights that Jodhpur reported the highest number of positive Measles cases (26.4%). Several other districts, including Ajmer, Bikaner, Barmer, and Jaipur, also contributed a significant proportion of cases. In contrast, districts such as Sikar, Sirohi, and Ganganagar reported no Measles cases, suggesting regional variations in disease incidence, potentially due to differences in vaccination coverage, healthcare infrastructure, or population density.

The study highlights the importance of Measles vaccination, as a significant proportion of Measles cases occurred in unvaccinated individuals. The highest burden of Measles was seen in younger children, particularly in the 1-5 year age group. The D8 genotype was the predominant strain in the study population, consistent with global trends. The vaccination coverage of 51% is below optimal levels for herd immunity, emphasizing the need for improved vaccination efforts, especially in rural areas where geographical disparities in disease prevalence were observed

1. World Health Organization. Manual for the laboratory diagnosis of Measles and Rubella virus infection. 2nd ed. Geneva: WHO; 2007.
2. World Health Organization. Measles Rubella strategic framework 2021-2030. Geneva: WHO; 2020. Licence: CC BY-NC-SA 3.0 IGO.
3. Centre for Disease Control and Prevention (CDC). Measles transmission [Internet]. 2023 [cited 2024 Oct 21]. Available from: https://www.cdc.gov/measles/transmission.html.
4. World Health Organization. Global Measles and Rubella strategic plan 2012-2020. Geneva: WHO; 2012.
5. Vaidya SR, Kamble MB, Chowdhury DT, Kumbhar NS. Measles & Rubella outbreaks in Maharashtra State, India. Indian J Med Res. 2016;143(2):227-31.
6. Lowang D, Dhuria M, Yadav R, Mylliem P, Sodha SV, Khasnobis P. Measles outbreak among children ≤15 years old, Jaintia Hills District, Meghalaya, India, 2017. Indian J Public Health. 2021;65.
7. Alam S, Hazarika N, Sarmah A, Sarmah N. A Retrospective Study of Measles Outbreak Investigation in North East India. Int J Curr Microbiol Appl Sci. 2015;4(8):399-405.
8. Singh K, Garg R. Outbreaks of Measles in Rajasthan in 2014: a cross-sectional epidemiological investigation. Int J Community Med Public Health. 2017;4:1751-7.
9. Wong BKC, et al. Impact of Mass Second-Dose Measles Immunization Campaign in India. Vaccine. 2019;37(32):4523-7.
10. Jallow MM, Sadio BD, Mendy MP, Sy S, Fall A, Kiori D, Ndiaye KN, et al. Measles and Rubella Incidence and Molecular Epidemiology in Senegal: Temporal and Regional Trends during Twelve Years of National Surveillance, 2010-2021. Viruses. 2022;14:2273.
11. Shakya AK, Shukla V, Maan HS, et al. Identification of different lineages of Measles virus strains circulating in Uttar Pradesh, North India. Virol J. 2012;9:237.