New CDC Report Shows Harmful Algal Blooms Are Making People and Animals Sick

Harmful algal blooms occur when there’s algae overgrowth in water. They can produce dangerous toxins that can make people and animals ill, or create dead zones in the water. A new report from the U.S. Centers for Disease Control and Prevention shines some light on the blooms’ health impacts.

The CDC recently shared a report on harmful algal blooms throughout the country in 2021, which showed, among other things, that 117 human illnesses and more than 2,700 animal illnesses were reported across 368 blooms in 16 states.

Aerial view of algal bloom

The report says, “The findings from this annual data summary indicate that HAB events and associated illnesses occur throughout the United States… Affected people primarily reported gastrointestinal, generalized, and dermatologic signs and symptoms, while affected animals—specifically dogs—presented with generalized, gastrointestinal, and neurologic signs.”

The agency added that in one particular event, at least 2,000 bats died, as well.

The blooms, which were voluntarily reported by public health agencies and their environmental health or animal health partners, were found to be most common during the summer and in freshwater bodies. Twenty-five percent of the blooms occurred in August, which was also when animal illnesses were most often reported, while the human illnesses were at their peak in June. For wildlife, the most common symptoms were urinary issues, while pets most commonly experienced gastrointestinal and general health issues.

Freshwater algal bloom

Harmful algal blooms are often intensified by human-related nutrient pollution, as well as warmer water temperatures. The U.S. Environmental Protection Agency says if you’d like to do your part to help minimize the impacts of the blooms, you can volunteer to monitor waterbodies, report suspected blooms to your state, and help prevent nutrient pollution.

You can also take action by signing this pledge to help prevent toxic algal blooms.

Blue green algal bloom
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