For the study released today, researchers dug into a CDC database of national reports of amoeba infections. They found 10 cases of people who developed infections with the free-living Acanthamoeba who also reported rinsing their sinuses. Of the 10 cases, five noted nasal rinsing that involved tap water, while the type of water used in the other cases was unclear. In water sampling, Acanthamoeba and other biofilm-associated amoebae have been detected in over 50 percent of US tap water samples.
Acanthamoeba is an opportunistic pathogen, and infections are rare, with only about three to 12 cases reported each year. But, when they do occur, they’re fatal about 82 percent of the time.
Of the 10 cases, nine occurred between 2015 and 2022, with one case included from 1994. In all of the cases, the people had some sort of immune-compromising condition, mostly cancer, but also solid organ transplant and HIV. This likely put them at higher risk for infection and severe outcomes.
Eight of the cases had evidence of disseminated infections, meaning the amoeba had dispersed around the body. Six of the cases developed Granulomatous Amebic Encephalitis (GAE), where the amoeba infects the brain and spinal cord. GAE has a less than 7 percent survival rate. Surprisingly, the passive surveillance data on amoeba infections reported to the CDC only noted deaths in three of the 10 cases, but the authors caution that the database doesn’t include follow-up information. So, it’s unclear if the people survived beyond the date of the amoeba infection report.
Overall, the researchers called for more education about using tap water for home medical uses, particularly among immunocompromised patients. They also highlight general advice from the agency: For nasal rinsing, the CDC recommends using boiled, sterile, or distilled water. “If tap water is used, it should be boiled for a minimum of 1 minute, or 3 minutes in elevations >1,980 meters, and cooled before use,” the researchers wrote.