What infectious disease could become the biggest threat in 2025? - As the world step into 2025, the threat of infectious diseases-- both familiar and new -- continues to be a pressing concern. Several factors, including declining childhood vaccination rates and potential shifts in U.S. health policy, may create conditions ripe for disease transmission.

A significant concern in 2025 is the declining rates of childhood immunizations, coupled with rising exemptions from school vaccination requirements. Adding to this, a potential shift in leadership at the Department of Health and Human Services (HHS) could bring vaccine skepticism to the forefront of public discourse. If Robert F. Kennedy Jr. is confirmed as the HHS head, his history of promoting vaccine-related conspiracy theories could influence public perceptions and reduce vaccine uptake. Although Kennedy denies being "anti-vaccine," his statements have cast doubt on the safety and efficacy of vaccines, raising alarms among health experts.

Dr. Perry N. Halkitis, Dean of the Rutgers School of Public Health, underscores the gravity of the situation, categorizing the challenges into three groups: reemerging diseases, currently spreading diseases, and potential new threats.

Five Infectious Diseases to Monitor in 2025

1. Bird Flu

In 2024, the U.S. documented its first severe case of bird flu in humans, among over 60 cases reported globally. While the Centers for Disease Control and Prevention (CDC) considers the risk of human-to-human transmission low, experts warn of potential outbreaks due to inadequate responses to bird flu among dairy cattle. Dr. Michael Osterholm, Director of the Center for Infectious Disease Research and Policy, stresses the need for a more robust strategy to address this growing concern.

2. Measles

A resurgence of measles, driven by declining vaccination rates, was evident in 2024 with over 280 cases reported—the highest in five years. Measles, a highly contagious and potentially severe illness, has primarily affected individuals who are unvaccinated or lack proper documentation of their immunization status. The rise in vaccine skepticism, exacerbated by anti-vaccine rhetoric, poses a risk of further outbreaks in 2025.

3. Polio

Polio remains a threat due to its persistence in countries like Pakistan and Afghanistan. In the U.S., the disease could resurface in populations with low vaccination coverage. Despite President-elect Donald Trump’s endorsement of the polio vaccine, skepticism surrounding its safety persists, partly fueled by misleading claims from influential figures. Public health experts emphasize the need to reinforce vaccination campaigns to prevent potential outbreaks.

4. Mpox

Mpox, a virus related to smallpox, continues to be a concern, especially among men who have sex with men. Although vaccines were initially distributed for free, their costs since April 2024 could deter at-risk populations from getting immunized. The emergence of a more aggressive strain in California further highlights the need for vigilance.

5. Disease X

“Disease X” refers to an unknown pathogen that could trigger the next pandemic. Health experts advocate for heightened preparedness to address the unpredictability of emerging diseases. Although recent fears of Disease X in the Congo were linked to severe malaria, the concept serves as a reminder of the need for global readiness.

Health experts agree that another pandemic is inevitable. Strengthening vaccination programs, investing in research, and fostering public trust in science are critical steps to mitigate the impact of infectious diseases in 2025 and beyond.