The monkeypox outbreak earlier this year taught Americans one simple but disturbing lesson: Gambian giant rats have a far easier time entering the United States than Gambians—or any other foreign national for that matter. Our immigration laws, by and large, are tougher on people than animals.

The widely reported public scare occurred after a pet trader imported several genera of African rodents, including one Gambian giant rat carrying the monkeypox virus. The infected rat landed at a pet wholesale outlet in Illinois and spread the virus to prairie dogs awaiting public sale. The infected prairie dogs then passed on the disease to more than 70 people throughout the Midwest.

This latest alien disease outbreak is the direct result of the U.S. government's appalling failure to control the flow of tens of millions of exotic creatures into this country for the pet trade.

It is not just monkeypox that jumped from animals to people. So did SARS. And so did HIV-AIDS, Hepatitis B, the hemorrhagic Ebola and Marburg viruses, Lyme disease, hantavirus, mad cow disease, and West Nile virus. A veritable Noah's Ark of exotic wildlife is being imported with few limits, and the viruses, bacteria, and parasites that these animals carry can transmit foreign contagions to native wildlife and to humans.

Many people may never encounter some of these disease-carrying creatures, such as the deer tick that carries the bacteria that causes Lyme disease. But many potentially problematic animals, particularly reptiles, are as close as your local pet store. What's more, pet dealers peddle everything from dangerous carnivores to omnivorous fish to venomous amphibians in stores, on the Internet, by mail-order catalog, at regional exotic auctions, and in local swap meets.

Despite their wide popularity, many seemingly harmless animals can be dangerous, especially to children. With large predators who are hard-wired to kill, the threat is palpable. Americans now own up to 15,000 pet tigers, lions, cougars and other big cats, with predictably tragic consequences. Nine people have been mauled to death, and scores badly injured in the past five years by tigers alone.

Other dangers are less obvious. More than seven million iguanas, snakes, lizards, and other reptiles are kept as pets in private homes, and fully 90% carry salmonella that can be life-threatening to children, the elderly and those with compromised immune systems. The Centers for Disease Control and Prevention reports more than 90,000 cases of salmonellosis are contracted annually from pet reptiles, calling it an urgent public health issue.

Three decades ago, the Humane Society of the United States successfully petitioned the U.S. Food and Drug Administration to ban the import and sale of small turtles because they carry salmonella. Since then, we have campaigned against this growing public passion for exotics, and tracked with alarm the pernicious consequences for both people and wildlife. The federal response has been to impose import bans on primates for the pet trade, on many species of wild-caught birds, and on three species of African tortoises that were carrying ticks harboring disease harmful to livestock and wildlife.

Yet, Washington has failed to stiffen the nation's defenses sufficiently, and we are now bearing witness to the consequences. Four years ago, for example, The HSUS again petitioned the FDA, this time for a ban on the sale of pet reptiles. Our petition was in response to the soaring incidence of salmonellosis, which causes severe diarrhea, fever, vomiting, even death. The agency has not yet responded.

Fanciers of unconventional pets—those people eager to obtain the latest fad animal for personal amusement, public recognition, or bragging rights—rarely stop to consider the true costs of the exotics trade. We now know that exotic animals pass on diseases which can wreak havoc with wildlife and sicken people. What's more, all forms of wildlife suffer extreme cruelties and high death rates during capture and transportation. Mortality during shipment among tropical birds and reptiles can run up to 80%.

The USDA has guidelines for importing pets and livestock. Dogs must be vaccinated for rabies; cats bound for Hawaii must be quarantined for 130 days; horses and livestock are subject to a raft of screening procedures. But what about Gambian giant rats and other obscure creatures?

Says a USDA spokesman: "We don't regulate importation of fish, reptiles, lions, tigers, bears, foxes, monkeys, endangered species, guinea pigs, hamsters, gerbils, mice, rats, chinchillas, squirrels, mongooses, chipmunks, ferrets, and other rodents."

The question is, why not?

The monkeypox outbreak has rattled the government, and the government has responded with emergency measures including an import ban on all African rodents. This is a prudent first step, but a more comprehensive approach is needed.

Washington should prohibit imports of all wild-caught animals destined for the pet trade—mammals, reptiles, amphibians and birds. Yes, the pet industry will fuss and growl, but a decisive public policy response will protect wildlife and people, and it won't diminish our quality of life. If a person wants a loving pet, there are millions of them at local animal shelters and breed rescue groups.

Wayne Pacelle is a Senior Vice President of the Humane Society of the United States.