The head of the World Health Organization said two days ago that there is no sign of a larger hantavirus outbreak following the evacuation of passengers from a disease-stricken cruise ship. 

That reassurance applies to an acute international event. It does not apply to a separate domestic trend that CDC data has been quietly documenting for three years.

According to CDC-reported case data, the United States recorded 38 hantavirus cases in 2025. 

That is the highest annual total in the six-year dataset, and a 192% increase from the 2022 low of 13 cases. 

The cruise ship is not why that number has been climbing. It was climbing before the cruise ship made international headlines.

TL;DR

• U.S. hantavirus cases rose from 13 in 2022 to 38 in 2025, a 192% increase and a six-year high, driven largely by western states.
• The WHO’s recent reassurance about no larger outbreak applies to a cruise ship incident; the domestic U.S. trend was already worsening independently

The Six-Year Trajectory

From 2022 through, the count has risen in each consecutive year, reaching a new six-year high each year for three straight years. 

New Mexico leads the dataset with 7 cases in 2025, matching its 2023 total, making it the most persistently affected state across all six years, with a cumulative total of 25 cases since 2020. 

Arizona recorded 6 cases in 2025 after a peak of 10 in 2024. 

California recorded 6 in 2025, up from just 2 in 2024 and zero in 2022. Nevada contributed 5 cases and Colorado 4.

In other words, the American Southwest and West are driving the increase. 

Why Cases Are Rising

Hantavirus Pulmonary Syndrome, the form prevalent in North America, spreads through inhalation of dust contaminated with infected rodent urine, droppings, or saliva. 

It is not transmitted person-to-person. 

The rising case counts reflect alternating drought and above-average precipitation across western states through 2020-2025, which has driven deer mouse population surges. 

Drought reduces predator populations; subsequent rainfall boosts vegetation and food supply; rodent numbers spike; and human exposure increases. 

The hantavirus case trajectory closely tracks that cycle.

An Unexpected Geographic Spread

One of the dataset’s more notable 2025 findings is the appearance of cases in states where hantavirus has historically been rare. 

Illinois, Kentucky, Maine, and West Virginia each recorded one case in 2025, with zeros in most, if not all, prior years. 

Hantavirus is classically associated with the rural American Southwest. 

Cases appearing in eastern states raise a question that CDC data cannot resolve from case counts alone. 

Are these travel-related diagnoses in which patients were exposed in western states and diagnosed at home, or early signals of the deer mouse reservoir expanding into new geographic territory? 

The answer matters significantly for how public health agencies communicate risk.

The next CDC weekly case report will show whether 2026 is tracking above or below 2025’s pace. 

Based on three consecutive years of year-on-year increases, there is no data-based reason to expect the trend to reverse without a change in the environmental conditions driving it.

ELI5 

Hantavirus is a dangerous disease spread by mouse droppings that kills about 1 in 3 people who get it, and there’s no vaccine. Americans have been getting it more each year, 38 cases in 2025, nearly three times the 13 cases in 2022. This was happening before a cruise ship made the news about hantavirus. 

Sources: 

CDC “Reported Cases of Hantavirus Disease” report (2020-2022); CDC weekly case reports (2023-2025)