What illnesses can be passed from pets to humans?

Health officials in Alaska recently reported the first known human death from a virus called Alaskapox.

The man, who died in January, lived in a wooded area and cared for a stray cat that hunted small animals, according to health officials. He had a weakened immune system and is thought to have contracted Alaskapox through contact with animals.

At around the same time, an individual living in Oregon was diagnosed with bubonic plague. Health officials suspect this person was infected by a cat. The individual is reported to be in early stages of the illness, and the patient and close contacts are being treated with antibiotics.

These infections are reminders that diseases from nonhuman animals can sometimes be transmitted to humans. To get a better sense of what such diseases are and what precautions pet owners and animal lovers should take to keep themselves and their animals healthy, I spoke with CNN wellness medical expert Dr. Leana Wen.

Wen is an emergency physician and adjunct associate professor at George Washington University. She previously was Baltimore’s health commissioner, where as part of her responsibilities, she also oversaw animal control and protection.

CNN: What types of diseases can household pets like cats and dogs transmit to humans?

Dr. Leana Wen: Just as humans can transmit diseases to other humans, animals can transmit diseases to others in their own species. Sometimes, animals can transmit diseases to other species, and that includes humans with whom pets have had close contact.

One way to classify the diseases that can be spread by household pets to humans is by method of transmission, such as the fecal-oral route. Someone who is in contact with the feces of infected animals could get the disease themselves if they don’t wash their hands well or if the fecal contents end up contaminating water or food that is then ingested by the human.

These diseases include bacterial infections like campylobacter and salmonella and parasitic infections like cryptosporidium, giardia and tapeworm.

Symptoms can include abdominal cramping, diarrhea, fever and vomiting. Depending on the illness, people may need targeted treatment, such as antibiotics or antiparasitic medications. The infections are generally mild, although they can be serious for people with underlying medical conditions and those who are very young or elderly.

There is a specific parasitic infection called toxoplasmosis that is associated with cleaning cat litter boxes or eating food or drinking water that has been contaminated with cat feces. Most people with this infection have little or no symptoms, but there is a unique risk to pregnant women because toxoplasmosis can be transmitted through the placenta. Their infants could become infected before birth and then develop serious neurological problems such as seizures, vision loss and mental disability.

A second route of infection is through scratches and bites. Cat scratch disease, for instance, is a bacterial infection spread when a cat scratches or bites a person enough to break their skin. It also can be spread if an infected cat licks a person’s open wound. People who are infected can develop swollen and painful lymph nodes, fever and headache.

Many people have heard of rabies, which is a deadly viral infection spread to humans through the bite of infected animals. Rabies is nearly universally deadly. Most domestic animals in the United States are vaccinated against rabies, but this is not the case in some other countries. Thankfully, there are rabies shots that can be taken after suspected exposure.

A third route of infection is through another vector such as ticks, fleas and mosquitoes. Ticks, for instance, can transmit infections that cause Lyme disease, babesiosis, ehrlichiosis and tularemia. These diseases spread when a person is bitten by an infected tick that has fed off an infected animal. Dogs that spend time in wooded habitats could have ticks that infect them, and the ticks could also spread the disease to humans.

CNN: What about Alaskapox and the bubonic plague? How could someone contract these diseases from animals?

Wen: Alaskapox is in the category of viruses called orthopoxvirus. There are several viruses in this category that can be transmitted from animals to humans, including mpox (formerly known as monkeypox) and cowpox, smallpox and vaccinia viruses. It’s not known how the man who died from Alaskapox contracted it, but a possible route is an infected animal biting the individual or exposure of an infected animal to an existing break in the man’s skin.

Bubonic plague is caused by the Yersinia pestis bacterium and can be transmitted through a break in the skin, too, if someone has an open wound and comes into contact with an animal’s infectious bodily fluids. It also could be transmitted through the bite of an infected flea.

CNN: What are steps people can take to reduce the risk of contracting diseases from their pets?

Wen: There are several important steps pet owners and animal lovers can take to protect themselves, their family members and their pets.

To begin with, they should ensure that their dogs and cats are fully vaccinated. Vaccines prevent not only many illnesses that can spread from animals to humans, but also diseases limited to the animal but that could be harmful and even fatal. Pets should also be cared for with regularly scheduled checkups.

It’s also important to take your pet to the veterinarian if it becomes ill. Try to reduce contact with sick pets in the meantime. Identifying the cause of the illness can prompt quicker treatment for the animal and possible testing and treatment for the human.

There are also common-sense precautions people should take to reduce disease transmission. This includes washing your hands well after handling feces and other waste. Make sure the pet’s living area is clean. Keep away from wild animals and animals that are behaving strangely.

Children who are helping out with cleaning litter boxes or picking up after their dogs should be reminded to wash their hands well. Kids should also be reminded to avoid kissing their pet’s mouth and reduce activities that could result in accidental bites. They should be sure to wash their hands after going to friends’ houses with animals and visiting farms with petting zoos. And it’s important to clean waste outdoors, including in your own yard, and not to let kids play in areas with animal feces.

To lower the risk of fleas, it’s important to maintain good hygiene and reduce rodents in and around the animal’s living space. To decrease tick-borne illness, look carefully for ticks after going to wooded areas and remove ticks right away after spotting them.

CNN: Does it mean no one should have animals?

Wen: Certainly not. People seek animal companionship for many reasons. For many people, having a dog or cat is essential to their own well-being and mental health. There are simple steps everyone can take to reduce the risk of animal-to-human disease transmission. Individuals who should take additional care include those who are immunocompromised, babies and pregnant women.