ABSTRACT:
Measles outbreak investigation in Lejweleputswa district, Free State Province, February - December 2025 Motshabi Modise1,2, Thobile Nokwazi Khanyile3,4,6, Sizwe Sipho Khumalo1,4,6, Katlego Mophosho2, Kholisiwe Nohaji2, Maggie Majenge2, Lindiwe Maku2, Lorraine Sauer2, Morubula Jack Manamela.3 Nishi Prabdial-Sing,3,6, Lehlohonolo Kumalo1,Boitumelo Fanampe2,6, Perpetual Chickobvu2, Kerrigan Mcarthy3,5 1Division of Public Health Surveillance and Response, National Institute for Communicable Diseases, a division of the National Health Laboratory Service, Johannesburg, South Africa. 2Free State Department of Health, Bloemfontein, South Africa 3Centre for Vaccines and Immunology, National Institute for Communicable Diseases, a division of the National Health Laboratory Service, Johannesburg, South Africa. 4 South African Field Epidemiology Training Program, Division of Public Health Surveillance and Response, National Institute for Communicable Diseases, a division of the National Health Laboratory Service, Johannesburg, South Africa. 5Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa 6Department of Medical Microbiology, Universitas Academic Laboratory, National Health Laboratory Service, Bloemfontein, South Africa

BACKGROUND:
Measles outbreaks continue to occur in South Africa despite the availability of highly effective vaccines. In March 2025, an outbreak alert was issued following a laboratory-confirmed measles case in the Lejweleputswa District, Free State Province, South Africa. The objectives of the outbreak investigation were to identify the source, evaluate the scale, and direct measures for public health action. Methods A descriptive study was conducted between February and December 2025 using laboratory surveillance data and the routine measles case investigation forms. Cases were detected through the laboratory and, active case finding, contact screening and health facility-based surveillance data. The Measles IgM laboratory test was used to confirm a case; that some cases were also confirmed through epidemiological link. Environmental assessment was conducted to determine contributing risk factors like hygiene, water supply, overcrowding and overall status of households.

RESULTS:
In total 767 suspected measles cases were reported, 219 of which were confirmed (214 laboratory confirmed and 5 confirmed by epidemiological linkage). Matjhabeng sub-district accounted for 120 (54.7%) cases. Fifty percent were children aged 5–9 years, with 62% being females. A 24% attack rate and a 0.4% case fatality rate was observed. The vaccination status of the four-month old female, hospitalised with negative results for Human Immunodeficiency Virus was complete. Of the 226 confirmed cases, 62 (28%) were fully vaccinated, one (1.3%) was inadequately vaccinated, 13 (5.9%) were unvaccinated, and 144 (64%) had unknown vaccination status. Environmental inspections uncovered hygienic and overcrowding deficiencies.

CONCLUSIONS:
The current outbreak highlights the continued threat of a measles resurgence in districts with inadequate vaccination coverages. Secondly, it showed the need to strengthen the immunization coverage. Given the high incidence in the 5–9-year age group, measles vaccination is to be included into the school health vaccination programme, to boost immunity in this group, with improved vaccination records.