Do you love your cat, hairballs and all? Watch out, because new research from the journal Trends in Parasitology has called cat poop a “vast and underappreciated” public health concern, CNN reports.

Here’s the deal: Some cat poop contains Toxoplasma gondii—a.k.a. toxo—a parasite for which felines are the primary carrier. The infective form of the parasite in cats are called oocysts. These oocysts can survive in moist soil for 18 months or longer after a cat buries its waste. A single infected cat can potentially deposit millions of parasitic oocysts over a very short period of time—alarming since it takes only one spore to infect a human with toxoplasmosis.

Doctors have known for a while that oocysts can be very dangerous to those with weak immune systems. For instance, toxo can attack the fetus of a woman if she is infected while pregnant. And the parasite can cause serious brain infections in those with immune system diseases such as HIV/AIDS.

What’s more, toxo and its antibodies are more prevalent in people with rheumatoid arthritis, brain tumors and mental disorders such as schizophrenia and obsessive-compulsive disorder (it may affect memory and other cognitive functions).

But just how prevalent is the danger? Think about how common cat poop is. At any given time, about 1 percent of cats in the United States are infected with toxoplasmosis. The American cat population (82 million domestic cats and 25 million to 60 million feral felines) can deposit 1.2 million tons of cat poop into the environment each year. That translates to at least 1 million infected felines and 10,000 tons of infected waste introduced into our environment each year.

The good news is indoor cats are generally not exposed to the parasite. Almost all infected cats live outdoors or are feral. Also, maintaining proper hygiene after changing your cat’s litter box nullifies much of the risk of exposure.

To stay safe, doctors suggest pet owners dispose of cat litter in the garbage and not flush it down the toilet where potentially infected water can enter into streams and lakes. In addition, pregnant women or those with compromised immune systems should not change litter boxes. Experts also suggest that children’s sandboxes and play areas should be covered when not in use and gardeners should always wear gloves while digging in the dirt. Most important: Wash your hands and all fruits and vegetables thoroughly before eating.

But here’s good news for cat lovers! Did you know that owning a cat might reduce the risk you’ll die of a heart attack? Click here to read more.