On 2 January 2023, an outbreak of Measles was confirmed in the city of Nepalgunj in Banke District, Nepal, following a cluster of cases of fever and rash, according to a press release issued by the World Health Organization on 14 March 2023. Following the confirmation and through active case search, the index case was identified, with the onset of symptoms on 24 November 2022. Between 24 November 2022 and 10 March 2023, 690 Measles cases, including one associated death (a case fatality ratio of 0.14 %), have been reported from seven districts in western Nepal, and three districts in eastern Nepal (mainly in the Terai lowlands of southern Nepal). The majority of the cases (591 or 86%) have been reported in children aged less than 15 years.
While Measles is endemic in Nepal and is reported every year, the magnitude and extent of the current outbreak are unusually high compared to the previous years. Only sporadic isolated measles cases have occurred since 2004, when a substantial outbreak of over 12 000 cases was reported. The risk of spread of Measles is assessed as high at the national level and moderate at regional level, due to the spread of the outbreak from Nepalgunj to other districts and provinces, the detection of Measles cases in a highly mobile population with frequent cross-border travel, and low population immunity of the affected districts. Response Measures in affected areas have been implemented, including active case search, case management and outbreak response immunization.
Between 24 November 2022 and 10 March 2023, a total of 690 Measles cases, including one associated death have been reported from seven districts in western Nepal (Banke, 327 cases; Surkhet, 62 cases; Bardiya, 49 cases; Kailali, 39 cases; Kanchanpur, 27 cases; Bajura, 13 cases, and Dang, 12 cases), and three districts in eastern Nepal (Mahottari, 103 cases; Sunsari, 34 cases; and Morang, 24 cases).
Number of Measles cases (690) reported in Nepal between 24 November 2022 to 10 March 2023. World Health Organization.
The outbreak started in Nepalgunj SMC, Banke District, Lumbini Province, western Nepal, after a cluster of fever and rash cases was reported on 29 December 2022. Measles was confirmed by the National Public Health Laboratory on 2 January 2023. Following the confirmation and active case search in Nepalgunj and adjoining municipalities, the first Measles case was retrospectively identified from Nepalgunj with a symptom onset of 24 November 2022.
The National Public Health Laboratory has also detected laboratory-confirmed Measles cases in eastern Nepal. The dates of the onset of the outbreaks in Mahottari, Morang, and Sunsari districts were reported as 24 December 2022, 23 December 2022, and 16 January 2023, respectively. These Measles outbreaks are ongoing and adequate outbreak response immunization must be undertaken to prevent spread of these outbreaks to adjoining districts.
The present outbreak is occurring in two clusters of districts in the southern part of Nepal bordering India. Due to the porous international border, and Measles being endemic in both Nepal and India, the country’s source of infection cannot be determined definitively without further molecular epidemiological studies.
Distribution of measles cases reported by district in Nepal between 24 November 2022 to 10 March 2023. World Health Organization.
Most of the cases (327 cases or 47%) were reported from Banke District in Lumbini Province, which borders India. Here, the routine immunization outreach session sites and microplan for immunization service delivery were not developed with community involvement, leading to very few outreach session sites, a lack of awareness, and a large number of children who missed the vaccination.
The majority of cases (591 cases or 86%) have been less than 15 years old. However, nine Measles cases have also been observed in people over 45 years, with the maximum age of a case being 73 years.
The outbreak occurs in a population with suboptimal population immunity, which is partly due to the disruption in routine immunization services during the COVID-19 pandemic, as well as the quality of nationwide Measles-Rubella supplementary immunization activities conducted in 2020. Over half of the cases (400 cases or 58%) are unvaccinated, of these 68% (272) were less than four years of age. Only 31% and 28% of cases in age groups 1-4 years and 5-9 years, respectively, have received two or more doses of Measles-Rubella vaccine, showing susceptibility in these cohorts. According to the WHO/UNICEF estimates of national immunization coverage, in Nepal, the national Measles-containing vaccine first dose and second dose coverage were reported to be 90% and 87% respectively in 2021.
Age distribution and vaccination status of Measles cases in Nepal from 24 November 2022 to 10 March 2023. World Health Organization.
Measles is a highly contagious disease caused by the Measles Virus, a single-strand RNA Virus belonging to the genus Morbillivirus, which also includes the Viruses that cause Canine Distemper and Rinderpest, as well as a variety of other diseases infecting domestic and wild Mammals. Transmission is primarily person-to-person by airborne respiratory droplets that disperse within minutes when an infected person coughs or sneezes. Transmission can also occur through direct contact with infected secretions. Transmission from asymptomatic exposed immune persons has not been demonstrated. The virus remains active and contagious in the air or on infected surfaces for up to two hours. A patient is infectious four days before the start of the rash to four days after its appearance. The virus first infects the respiratory tract before spreading to other organs. There is no specific antiviral treatment for Measles and most people recover within 2-3 weeks.
Thin-section transmission electron micrograph of a Measles Virus.
Among young and malnourished children and immunocompromised people, including those with HIV, cancer or treated with immunosuppressives, as well as pregnant women, Measles can cause serious complications, including blindness, encephalitis, severe diarrhea, ear infection, pneumonia, and death.
An effective and safe vaccine is available for prevention and control. The Measles-containing vaccine first dose is given at the age of nine months, while the second dose of the Measles-containing second dose is given at the age of 15 months. A 95% population coverage of both doses is required to stop Measles circulation.
In areas with low vaccination coverage, epidemics typically occur every two to three years and usually last between two and three months, although their duration varies according to population size, crowding, and the population’s immunity status.
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