It’s painful for me to look at Joe. He’s very thin; the angles of his face have sharpened, his shoulder blades show through his skin, his legs are nothing but bones. His black hair had lost its luster, his emerald eyes are dim. Even his voice is an echo of its former fullness. He spends his time sleeping.

Joe’s immune system is losing its grip, and there is little to do about it. For him, there are no protease inhibitors, viral-load tests, Bactrium or even AZT. Joe doesn’t have HIV; he has FIV--feline immunodeficiency virus. Joe is my cat.

After 12 years with me, he is much more than a pet. He’s the loyal companion who has moved with me around the country, into and out of eight apartments and as many relationships. He was waiting for me when I came home one September night in 1988 after testing positive for HIV, and in the years since he has waited for my return from visits to doctors’ offices and too many trips to hospitals to see friends. I held onto him and cried when I learned last year that an ex-lover had AIDS. And he alone witnessed--not without some feline disdain--my momentary madness when I yelled and punched the wall of my apartment after finding out about the death of another former boyfriend last year.

An uncharacteristically dependent cat, Joe has always demanded endless attention, usually in the form of prolonged petting or stationary body positions that afford a soft, warm place to nap. In these moments, with him loudly purring his satisfaction and security, I was able to shut out, at least for a while, the relentless intrusion that HIV is in my life. But that changed when Joe’s doctor told me he had FIV. Now, watching him slowly pick his way toward me and leap uncertainly into my lap, I realize how life’s ironies can be too cruel.

The two viruses threatening our health are similar. FIV was identified in 1986, two years after HIV, by scientists who noticed an AIDS-like condition in cats. Like HIV, FIV is a retrovirus with a long latency period; it’s found in blood and saliva. It’s symptoms include mouth infections and chronic diseases of the lungs, intestines and urinary tract.

Researchers have divided FIV infection into five AIDS-like stages. The first immediately follows infection, lasts weeks or moths, and involves fever, low white-blood-cell counts, enlarged lymph nodes, diarrhea, even depression. Stage two is the asymptomatic period. Stages three and four are associated with increasingly severe chronic infections that send cat owners and their pets to the vet. In stage four, many cats die from the infections, and many owners choose euthanasia. Less than 10 percent of FIV-infected cats reach stage five, characterized by weight loss, anemia and more infections. Life expectancy in stage five does not exceed six months.

FIV is seen only in domestic cats that go outdoors, and usually in mature males. It’s transmitted mainly through biting that takes place during territorial fights. Joe grew up on the streets and in the backyards of New York City’s East Village. A veteran scrapper, he loved to go on midnight rambles that sometimes lasted for days and took him who knows where. During those years, the same could be said about my own nocturnal explorations.

Joe and I now live in San Francisco, where life is reputedly less stressful than in New York. Rather than dragging dead rats or baby birds into a tenement, he now spends his days following the sun from room to room or dozing on the deck. Appetite permitting, he still comes running, barely, when he hears me scraping the inside of the food can and the sound of the spoon clinking against his bowl. But what most excites him is the changing of the litter box--something that can’t happen often enough for his taste.

In moments of worry about my health, I used to wonder which of my friends would take care of Joe if I became unable to care for him myself. I don’t ask that question anymore. I know I’ll be around to do that. I’m holding my viral stalker at bay with 3TC and AZT, and have protease inhibitors and the next generation of drugs to keep me going for some time. Joe has only me, the scraping of the cat food can and the promise of a fresh litter. For 12 years he’s been there for me. Not it’s up to me to make sure there’s a warm lap for him to snuggle in as long as he wants one.