Global Disease Outbreaks: A 2025 Snapshot and Implications for the U.S.

Each year, there are multiple infectious disease outbreaks (defined as the occurrence of cases of disease in excess of what is expected) throughout the world. Some of these become severe and have global and domestic implications, including, most notably, the COVID-19 pandemic, but also the 2002-2004 SARS outbreak in China and eventually 28 other countries and the 2014 Ebola outbreak in West Africa. Since outbreaks are an ongoing reality and threat to human health, understanding the current status and scope of global disease outbreaks is important for stemming further spread to other geographic areas and populations, providing advice to travelers, and identifying the types of medical countermeasures that might be needed. While historically the U.S. government has played a key and often lead role in responding to outbreaks throughout the world, particularly in low- and middle-income countries, understanding the extent of outbreaks takes on added importance now, given changes made by the Trump administration. These changes include reduced funding, reductions in the number of U.S. staff supporting international outbreak response efforts, and elimination of some offices and functions, actions which collectively have diminished current U.S. government capacity to respond to outbreaks at home and abroad, even as experts believe another costly pandemic may strike the world within 25 years. There may a renewed opportunity, however, to mitigate some of these risks with the release of the State Department’s new U.S. global health strategy, which includes global health security as one of its three pillars.

To better understand the current outbreak landscape around the world, and because there is no single database of all global outbreaks, we analyzed data from multiple official sources to develop a snapshot of the number, type, and location of disease outbreaks, with human transmission, that have occurred thus far in 2025. Based on this analysis, we identified more than 100 outbreaks, including some that have affected multiple countries and impacted large populations. This finding is broadly similar to an estimate from a prior study of the 1996-2023 period that identified an average of 108 outbreaks that occurred each year. However, given that 2025 is not yet over, there could be more outbreaks in the weeks and months ahead. Our finding is also likely an underestimate due to delays in reporting and other factors (see methods for more information).

Findings

Our analysis finds that thus far in 2025 (see Table 1):

• We identified 102 reported disease outbreaks with human transmission in 66 countries as of October 10, 2025; this is likely an undercount due to delays in reporting, the multiplicity of outbreaks that may be captured in this analysis as a single outbreak (e.g., the United States has identified 44 distinct outbreaks of measles as of Oct. 7 this year), and other factors.
• These outbreaks are due to 20 different infectious diseases spanning a wide variety of disease types (including respiratory, vector-borne, food or waterborne, and direct contact infections) and including avian influenza (H5N1), Chikungunya, cholera, Ebola, Marburg, measles, mpox, Nipah, Rift Valley fever, yellow fever, and Zika, among others.
• There is significant geographic variation in the occurrence of outbreaks by region. The greatest number of reported outbreaks have been in sub-Saharan Africa (33 countries), followed by the Western Hemisphere (15), East Asia and the Pacific (7), South and Central Asia (6), and the Near East (Middle East and North Africa, 5).
• A third of these countries (23) countries have experienced more than one outbreak this year, often of varying scales. For example, the Democratic Republic of the Congo has reported outbreaks of anthrax, cholera, cVDPV1, Ebola virus disease, mpox, and one outbreak due to an unexplained cause but described now as “acute febrile illness,” and the United States has reported outbreaks of dengue – which is not endemic in the continental U.S. but has caused localized transmission from travel-related imported cases – and measles, which had long been considered eliminated in the U.S., a status that is now at risk due to increasing cases.
• Outbreaks have ranged in size, as measured by number of cases as well as the number of affected countries. For example, a single case of Chapare hemorrhagic fever constituted an outbreak in Bolivia, while the largest this year has been the cholera outbreak across 34 countries, which has approached a half million cases and been declared a health emergency by the World Health Organization.
• Similarly, the number of deaths resulting from these outbreaks has also varied widely, as some virulent infectious diseases have led to high mortality, such as deaths among all suspected cases of Marburg virus disease (10 of 10) and deaths among two-thirds of suspected cases of Ebola virus disease (43 of 64). Others have resulted in few deaths but spread rapidly and can have important health impacts, such as chikungunya and mpox.

Table 1

Disease Outbreaks, 2025