Most of it is rare, most of it is Salmonella, and nearly all of it comes down to hands, kitchens, and who in the house is under five.
Who actually gets ill
Four groups: children under five, adults over 65, anyone pregnant, and anyone with a weakened immune
system, whether from illness or from treatment such as chemotherapy, steroids or drugs for autoimmune
disease. Nearly every figure on this page is driven by the first group. Small children touch everything,
then put their hands in their mouths.
The CDC rule for under-fives
Children under five should not handle or touch reptiles, amphibians, poultry including chicks, or
rodents, or anything from their enclosures. Reptiles and amphibians are not recommended at all in a house
with a child under five, an adult over 65, or anyone immunocompromised. Ferrets are not recommended with
children under five either, mostly because of bites.
Two extra rules for pregnancy: toxoplasmosis from cat litter, and lymphocytic choriomeningitis virus
from rodents. Both are covered below.
Dogs
Campylobacter. Diarrhea, fever and cramps for about a week. Healthy dogs carry it, and pet-shop
puppies are the known problem: an outbreak between 2016 and 2018 made 118 people ill across 18 states, 95%
of them after contact with a pet store puppy, and the strain resisted seven antibiotics.
Leptospirosis. Spread in urine, survives weeks in wet soil and water. Almost every dog is at
risk, town or country. In people it starts like flu and can go on to kidney or liver failure. There is a
dog vaccine, and AAHA now calls it core.
Roundworm and hookworm. Eggs pass in feces, mature in soil, and get into children who play in
it. Roundworm can damage a child's eye or sight. Hookworm larvae get in through bare skin and leave itchy
red tracks. Pick up every time, cover sandboxes, deworm on the vet's schedule.
Rabies. Rare in US dogs because of vaccination, but any bite from an unknown animal is treated
as a possible exposure. About 100,000 Americans a year get post-exposure vaccination; fewer than 10 die.
Wash a bite with soap and water at once and call a doctor.
Bites. One in five dog bites needs medical attention, and children are bitten more often and
worse.
Ringworm is a fungus, not a worm, and passes easily from pets to people. Giardia from a
dog is unlikely: the type that infects people is usually a different one.
Raw food. The CDC does not recommend feeding raw. Salmonella and Listeria have been found in
raw pet foods, and freezing or freeze-drying does not kill them all. The risk is to the people handling
the food and the bowls as much as to the dog.
Cats
Toxoplasmosis. Passed in cat feces. Over 40 million Americans carry the parasite; most never
know. The danger is in pregnancy, where it can cause miscarriage or lasting damage to the baby's eyes or
brain. The parasite is not infectious until one to five days after the cat passes it, so a litter box
cleaned daily is a safe one. If you are pregnant, have someone else change it; if there is no one, wear
disposable gloves and wash afterward. Do not take on a new cat or handle strays while pregnant, keep cats
in so they do not hunt, and do not feed raw meat.
Cat scratch disease. Bartonella, carried by fleas and found in the blood of up to one in three
healthy cats, kittens most of all. A scratch that barely breaks the skin can give you a swollen gland and a
low fever one to three weeks later. Between 20% and 80% of cat bites and scratches get infected. Flea
control is the prevention. Wash scratches with soap and water. The CDC advises people with weakened
immunity to avoid cats under a year old.
Roundworm, hookworm, ringworm and rabies as for dogs. Cats that go outdoors and use garden beds
are why the CDC says wear gloves to garden and cover the sandbox.
Rabbits, guinea pigs, hamsters, rats and mice
Salmonella. Carried by healthy-looking animals. A guinea pig outbreak between 2015 and 2017
reached eight states.
Lymphocytic choriomeningitis (LCMV). A virus of house mice that hamsters and pet mice pick up.
Spread by fresh urine, droppings, saliva and bedding. Flu-like at first; in pregnancy it can cause
miscarriage or serious birth defects, which is why the CDC says pregnant women should not handle pet
rodents. Seventy percent of immunocompromised people who catch it die.
Rat-bite fever. In the mouths of rats, mice, gerbils and guinea pigs as a normal resident.
Spread by bites and scratches but also by kissing a pet rat or handling bedding. Fever, vomiting, headache
and joint pain three to ten days later. It can be fatal.
Seoul virus. Pet rats, no signs in the rat. In 2017 an outbreak through breeders reached 17
people in 11 states. Disinfect cages and bedding with a 10% bleach solution.
Ringworm as above.
The CDC's rules for small mammals: do not kiss them, snuggle them or hold them near your face; keep them
and their gear out of the kitchen; never clean a cage in a food sink; use a laundry sink or the bath and
disinfect it afterward; do not let them roam the house unsupervised.
Ferrets
Ferrets catch human flu and can pass it back. There is no ferret flu vaccine, so keep away from the
ferret when you have it. They carry Salmonella and Campylobacter, and a ferret bite can spread rabies if
the ferret is unvaccinated, so vaccinate. Not recommended in homes with children under five.
Budgies, cockatiels and other birds
The one that matters is psittacosis, a bacterial pneumonia caught by breathing dust from dried
droppings. Parrots and cockatiels carry it, sick or apparently well. Symptoms come 5 to 14 days later: dry
cough, fever, headache, aches. Treated, it kills fewer than one in a hundred. Wet the cage before cleaning
so nothing goes airborne, never dry-sweep, and never wash cage gear in the kitchen sink.
Bearded dragons, geckos, snakes, turtles and tortoises
Reptiles carry Salmonella in the gut as a matter of course. A healthy animal, a clean tank, a vet
visit, none of it removes the bacteria, and the tank water carries it too. This is the single most common
pet-to-person infection, and it is a disease of small children.
Turtles under four inches have been banned from sale since 1975 because children put them in their
mouths; the ban prevents an estimated 100,000 child infections a year. They are still sold illegally at
souvenir shops, street stalls and online. A 2024 outbreak made 63 people ill, median age 8; of those who
gave the size, 93% had a turtle under four inches.
Bearded dragons: 26 ill in 2024, median age one year; 20 ill in 2025, half under five, one death. At
least one child never touched the dragon and was infected from surfaces where it had roamed.
Geckos, including leopard geckos: 113 ill across 36 states between 2024 and 2025.
Snakes: the frozen feeder rodents carry it. A 2014 outbreak through feeder mice made 41 people ill.
Thaw them in a container kept for the purpose, never in the kitchen sink.
Axolotls are amphibians and every rule above applies, tank water included.
Fish
You do not have to touch a fish to catch something from it. Tank water, gravel and equipment carry
Salmonella, Aeromonas and the mycobacterium that causes fish tank granuloma, a slow skin infection that
gets in through a scrape from gravel or a fin. Wear gloves to work in the tank if you have any cut on your
hands. Empty tank water into the bath or a laundry sink, not the kitchen, and disinfect afterward.
Children under five do not clean tanks.
The rules that cover almost all of it
Wash hands with soap and running water after touching any animal, its food, its enclosure or its
mess, and before eating. Supervise children under five while they do it.
Pets and their equipment stay out of the kitchen. No habitat, bowl, cage or tank is ever cleaned in a
food sink.
Do not let children kiss pets or put their hands in their mouths after handling one.
Keep vaccines, deworming and flea and tick control current. Most of what a cat or dog can give you
rides on a parasite.
Any bite that breaks the skin: wash it with soap and water immediately, then call a doctor.