Another group of victims has been hit by one of the most unusual diseases ever recorded in this country, a type of immune system breakdown that started among homosexual men but now continues to spread to new populations across the country, according to doctors at the Centers for Disease Control here.

The CDC announced today that people with the blood disorder hemophilia are now also vulnerable to the puzzling, and often fatal, ailment. The announcement came one week after the federal agency reported scores of new cases among Haitian refugees in this country.

The disease, which CDC officials have said is reaching epidemic proportions, is unlike any other reported in medical history. As of July 8, it had killed more than 177 of its 452 identified victims--twice the number killed by toxic shock syndrome, which the CDC also investigated.

Scientists have characterized the disease as a breakdown of the body's immune system, which defends it against a variety of diseases. The victims then contract many diseases typical of people whose immune systems have failed.

The leading killers among those diseases are a type of skin cancer called Kaposi's sarcoma and a deadly pneumonia called pneumocystis carinii. Both diseases are normally quite rare, but they are now appearing at several hundred times their expected rate in the population.

The danger of the ailment spreading is much greater now. "The number of cases is increasing, and the proportion of cases among people who are not homosexuals is also increasing," said Dr. Harold Jaffe, one of the leaders of the CDC task force trying to understand the mysterious outbreak.

"Until about June we were getting reports of cases at the rate of about five or more per week. In the last six weeks, we have been getting 15 to 20 cases per week," Jaffe said.

There are now 20 people working full time and another 30 working part time at the CDC to find the cause of the immune system failure.

When the task force was first formed last year and nearly all the victims were homosexual men, investigators believed the agent of the disease might have been a virus that is transmitted sexually, or an immune-suppressing drug or chemical that might have been in common use among homosexuals.

But there are now about 10 to 20 victims, men and women, who are not homosexual and seem otherwise healthy and drug-free.