Measles outbreak dynamics and mitigation strategies in Tijuana, Mexico, 2025–2026

Background

Measles remains a highly contagious vaccine-preventable disease. During 2025–2026, Mexico experienced its largest measles outbreak in recent years, with 15,277 confirmed cases nationwide. Border cities such as Tijuana are high-risk settings due to population mobility and immunity gaps. This study characterizes the local outbreak and evaluates the public health response.

Methods

Descriptive analysis of surveillance data from suspected measles cases reported in Tijuana between December 2025 and April 2026. Variables included case classification, age, vaccination status, and spatiotemporal distribution. Response activities were assessed using operational indicators: blocks covered, households visited, and vaccine doses administered.

Results

Of 193 suspected cases, 22 (11.4%) were confirmed, while 171 (88.6%) were discarded. Cases peaked in February–March 2026 and remained highly clustered, with 93.0% concentrated in Tijuana and limited spread to surrounding areas. Median age was 5 years (range: 0–62), with 48.6% under 5 years. Among confirmed cases, 56.3% were unvaccinated. Control measures covered 1,315 blocks and 16,804 households, with 690 vaccine doses administered (∼0.04 doses per household). Despite high transmissibility, the outbreak showed spatial containment and no sustained expansion, consistent with reduced effective transmission.

Conclusions

The outbreak was driven by immunity gaps in young children but remained geographically contained. Intensive prevention actions, including active case finding and targeted ring vaccination, were key to limiting propagation. In contrast to the large national outbreak, the controlled spread in Tijuana highlights the effectiveness of rapid, localized interventions. Strengthening routine immunization and data-driven microplanning is essential in high-mobility border settings.

Key messages

• Rapid field interventions, including active case finding and ring vaccination, were critical to containing measles transmission in a high-risk, highly mobile border setting.

• Despite the national outbreak, a timely local response contained transmission in Tijuana, highlighting the importance of epidemiological containment measures and fieldwork.