Top Infectious Diseases of 2025: Biggest Outbreak Risks and Symptoms

From sudden outbreaks that strained health systems across the world to major breakthroughs in disease surveillance and prevention, this entire year has been a turbulent one, yet it has come with a lot of transformations concerning infectious disease control. Widespread cases of bird flu, measles, malaria, and COVID-19 emerged in the midst of a warming climate and ongoing regional conflicts. Most of these diseases have been vaccine-preventable, but have become a center point due to the cutting of vaccine programs and vaccine hesitancy, especially in the United States. At the same time, enhanced public health measures saw deadly diseases like Ebola and M-Pox rapidly contained before mass devastation occurred. Here is a list of infectious diseases that made

headlines in 2025 and need to also be curbed in the coming year to prevent widespread devastation.

Hepatitis

Hepatitis B and Hepatitis C are among the most common infections in 2025. According to doctors, chronic hepatitis damages the liver and can even lead to cancer if it is not diagnosed or treated. Hepatitis is a big concern among experts since it spreads mostly through contaminated food, unsafe water, blood, and sexual contact. Many people may not show symptoms until serious liver damage occurs.

Bird flu

The first US death from bird flu, also known as avian influenza or H5N1, was reported by the Louisiana Department of Health earlier this year. The affected individual, said to be more than 60 years old, had underlying medical conditions and developed severe illness. Even though thereafter no cases of human-to-human transmission were reported, a multistate outbreak was identified among dairy cattle, alongside widespread transmission in wild birds and sporadic outbreaks among poultry, other mammals, and workers in affected industries. Apart from Louisiana, human cases were also confirmed in several US states: California, Colorado, Iowa, Michigan, Oregon, Texas, Washington, and Wisconsin. The CDC emphasized that the overall public health risk remained low due to the lack of concerning virologic changes.

Mpox

In 2025, Mpox remained a significant global concern, shifting focus from the 2022 clade II outbreak to surging Clade I cases in Africa - especially DRC, Sierra Leone, and Malawi, with higher severity. Doctors said the key concerns included Clade I's increased virulence and potential for broader community spread, mutations potentially affecting transmissibility, and challenges in public health responses, with the World Health Organisation issuing warnings for both Clade I and IIb outbreaks.

Malaria

Among the top infectious diseases that headlined across the world were malaria and its resurgent outbreaks, which are driven by factors like climate change, urbanization, and healthcare system vulnerabilities. Malaria remained a major global health concern, particularly in Asia and now even in the United States. According to studies, Malaria saw an estimated 282 million cases and 610,000 deaths worldwide. Experts believe antimalarial drug resistance poses a significant threat to global progress in curbing the infection.

Measles

Widespread outbreaks were observed in the United States, Cameroon, DRC, and Afghanistan – mostly in the urban areas with low vaccination coverage, as well as resurgences in high-income countries like Canada and Romania due to vaccine hesitancy.

Respiratory infections

Common influenza infections and COVID-19 have remained the most deadly respiratory infections apart from Respiratory Syncytial Virus, or RSV, which has been a headline infectious disease. According to experts, influenza cases are rapidly rising, and most of these infections are now surging among younger kids. While COVID-19 remains present, it is generally at lower national levels, with concerns around new variants and potential outbreaks like the Avian Flu still monitored. This category, including new COVID-19 variants and common influenza, remained the most widespread, affecting vulnerable populations such as the elderly and infants.