At a glance
- Naegleria fowleri, known as the "brain-eating ameba," can cause a rare but deadly brain infection called primary amebic meningoencephalitis (PAM).
- CDC data show that male children and teenagers are most at risk of getting PAM.
- States with warmer climates have the most PAM cases, but they do occur in northern states as well.
PAM cases by state
The map shows 173 U.S. PAM cases by state of exposure from 1937 to 2025. Many people were exposed to Naegleria fowleri through swimming in warm, fresh water, such as lakes and ponds. Texas and Florida had the most PAM cases, followed by Virginia and California. Location of exposure was unknown for 7 PAM cases that occurred during this period.
PAM cases by year
PAM cases are rare. A total of 180 cases were diagnosed in the United States from 1937 to 2025, ranging from 0 to 8 cases per year. Cases from 1937 to 1961 were diagnosed retrospectively.
PAM cases by age group and sex
PAM cases occurred more often in males than females for nearly all age groups. The highest number of cases, 45, occurred among males ages 10 to 14 years. Age and sex were unknown for 1 case.
PAM cases by month of illness onset
Naegleria fowleri thrives in warm, fresh water. The data show that 157 PAM cases diagnosed from 1937 to 2025 most often occurred during July and August, which may correlate with increased water exposure during warmer months. The month of illness onset was unknown for 23 cases.