A massive, multi-country diphtheria outbreak that has been raging across Sub-Saharan Africa since 2023 has grown large enough to trigger a new Level 2 Travel Health Notice from the U.S. Centers for Disease Control and Prevention, issued June 2, 2026, covering seven countries: Chad, Guinea, Niger, Nigeria, Mali, Mauritania, and Somalia. The notice instructs all travelers to affected areas to ensure they are up to date on diphtheria vaccination before departure — a recommendation that highlights a troubling gap in American adult immunization, since diphtheria boosters are required every 10 years and many adults have not received one since childhood.
The scale of this outbreak is difficult to overstate. From January to November 2025 alone, a total of 20,412 suspected diphtheria cases, including 1,252 deaths, were reported across eight WHO African Region member states — Algeria, Chad, Guinea, Mali, Mauritania, Niger, Nigeria, and South Africa — giving an average case fatality ratio of 6 percent. Several of these countries have been experiencing ongoing outbreaks since 2023, meaning this outbreak has now lasted more than two full years without being contained. Women, children aged 5 to 18 years, and young adults under 30 were the most affected populations, confirming that the immunity gap extends well beyond early childhood.
