A Toxic Algae Bloom Might Have Killed a Family of 3 and Their Dog in California—Here's What You Need to Know

The deaths are considered a "very unusual, unique situation."

On Monday night, authorities started searching for three missing people in California: John Gerrish, Ellen Chung, and their one-year-old daughter, Miju. Shortly after the search began, the family's vehicle was found in Mariposa County, California, and the bodies of the missing individuals, in addition to their dog, were found nearby, according to a statement from the Mariposa County Sheriff's Office. The family were found on a hiking trail in the Sierra National Forest.

Kristine Mitchell, a spokesperson for the sheriff's office, told the Associated Press, "This is a very unusual, unique situation. There were no signs of trauma, no obvious cause of death. There was no suicide note."

Toxic Algae Blooms Looked at as Possible Cause of Death for Family , Green algae on water surface due to pollution of phosphates , Phosphates feed algae, which grow out of control in water ecosystems and create imbalances, which destroy other life forms and produce harmful toxins
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Now, authorities are questioning whether toxic algae blooms were responsible for the deaths. Per the Associated Press, the bodies of the deceased have been transported to Mariposa's coroner's office so they can be autopsied and toxicology exams can be conducted, and the State Water Resources Control Board announced it was testing local waterways for toxic algae blooms, per reporting from CBS News.

In an interview with the Fresno Bee, Mariposa County Sheriff Jeremy Briese also said investigators were considering toxic algae blooms as a possible cause of death, but added that they're "unsure." He added that the algae blooms were "due to the recent drought," but that he doesn't "know too much detail about the toxicity of them."

The Fresno Bee also reported that Sierra National Forest shared information on its Facebook page on July 13 regarding water testing results that showed "a high concentration of algae bloom."

"The Sierra National Forest (SNF) would like to inform those visitors who like to enjoy this area of the Merced River and SNF, not to swim, wade or allow their pets to enjoy the water," the Facebook post stated. "Some species of algal mats can produce toxins, the agency continued, "and if present, can pose a risk to humans and pets."

What exactly are toxic algae blooms?

Toxic algae blooms, which are also known as harmful algal blooms (HABs), can form when excess nutrients are transferred from land to water, Nandita Basu, PhD, associate professor of water sustainability and ecohydrology at the University of Waterloo in Canada, tells Health.

Basu explains it like this: When humans deposit nitrogen and phosphorous onto plants to make them grow—usually through fortified fertilizers—those chemicals can end up in nearby bodies of water when crops being grown don't fully absorb the extra nutrients.

Those excess nutrients, in turn, cause algae growth: "Whey they run off, they are food for whatever is growing [in the water]," Basu says. "They promote the growth of algae. Some of these blooms are more toxic in nature." Right now, experts don't know why some of the blooms are toxic while others aren't, but research is being done on what kinds of factors—such as wind conditions and temperature—might affect this, Basu explains.

According to the Centers for Disease Control and Prevention (CDC), harmful algal blooms can be found in saltwater and freshwater, as well as brackish (a mixture of the two). They've been found across the US, Basu says, and they look like "foam, scum, mats, or paint on the surface of the water," per the CDC, which adds, "A bloom can change the color of the water to green, blue, brown, red, or another color."

How are toxic algae blooms harmful for humans and animals?

It's been well documented that pets and livestock can die from drinking toxic algae blooms, Basu says she can't recall a case where a human has died after exposure to them. "The California case is the first I have heard with people, and it is concerning," Basu says, adding that toxic blooms are showing up more often in areas of the country that were thought to be more pristine.

In humans, toxic algae blooms are more likely to cause gastrointestinal upset, due to liver toxins known as microcystins, according to the National Centers for Coastal Ocean Science. The symptoms humans often present with after coming into contact with harmful algal blooms depend on a number of factors, including how long you were in contact with the algae. The symptoms, per the CDC include:

  • Stomach pain
  • Diarrhea
  • Vomiting
  • Headache
  • Neurological symptoms (like dizziness and muscle weakness)
  • Throat, skin, nose, or eye irritation

If you think you have been exposed toxic algae blooms at all, you should contact your doctor or a poison control center. Since animals can get sick and die quickly after being exposed to toxic algae blooms, you should seek veterinary care ASAP if you think your pet has come into contact with them. You'll also want to report any illnesses to your local or state health department, to possibly avoid others from coming into contact with the toxic algae blooms.

Basu says that the dangers of toxic algae blooms highlight why you shouldn't drink water from lakes or ponds when you're out camping or hiking: "I think we really have to kind of accept the reality of the world we live in: There are a lot of these events where even lakes that were more pristine are showing occurrences of [toxic] blooms."

The CDC says that if you see a bloom in the water, it's best to stay out of it (and keep your pets out of it, too). You shouldn't fish, boat, or swim in water that looks discolored or smells bad, per the CDC, which adds that you should also avoid water that "has dead fish or other animals washed up on its shore or beach."

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