Doctors Are Trying to Find the Answers : Medical: Johnson’s physician says Laker star contracted HIV through heterosexual activity.

Earvin Johnson is believed to have contracted the virus that causes AIDS through heterosexual contact, the Lakers’ team internist said Friday.

But on the day after the 12-year NBA superstar announced that he was retiring from professional basketball because he was infected with the immunodeficiency virus (HIV), some questions still linger.

Johnson’s physician, Dr. Michael Mellman, said he does not know when Johnson contracted the virus. But, based on Michigan state law, Johnson had the opportunity to be tested for HIV infection when he and his fiancee, Cookie Kelly, applied for a marriage license in September.

Based upon current medical research, the scenario painted by Mellman indicates that Johnson falls into the least likely category of those who contract the virus.

“We cannot determine when, but since he is neither homosexual nor an (intravenous) drug user and he has not received a transfusion in the past, there is no data to suggest any other avenue of attaining the virus,” Mellman said in a statement released by the Lakers in Phoenix, where the NBA team played the Suns Friday night.

AIDS experts said Friday that it is less likely for an infected woman to transmit the virus to a non-infected man through sexual intercourse than it is for a man to infect a woman.

According to the U.S. Centers for Disease Control, 10,989 cases, or 6% of the total cases in the United States, were transmitted through heterosexual contact.

Wilbur Jordan, an AIDS specialist at the Drew University of Science and Medicine in Los Angeles, said scientists believe a smaller percentage of the virus is found in vaginal fluids, possibly making it more difficult for women to infect male sexual partners.

The virus is passed through the exchange of bodily fluids, during sex with an infected partner, by way of blood transfusion or in the process of sharing contaminated intravenous needles.

Jordan said another reason it appears to be difficult for a woman to infect a man during sexual intercourse is because the infected vaginal fluid must find its way into the man’s body.

“It is very hard to get into (the) penis unless (there is) an open sore on the penis or (they) are having rough sex,” Jordan said, adding that it is easier to become infected through oral sex.

The risk is considered to be lower for heterosexual contact than in homosexual contact largely because the fraction of heterosexuals now infected is much smaller than that of homosexuals, experts said.

Still, questions remain about the risk of getting HIV. Some doctors contend the risk for heterosexual men is slim, others argue that researchers do not have enough evidence to say either way.

Michael J. Scolaro, director of AIDS Research at the St. Vincent Medical Center Los Angeles Oncologic Institute, said it is paramount to assume there is 100% risk because not enough is known about transmission.

Scolaro, a professor at the USC School of Medicine, said if an infected woman is starting a menstrual period with some blood flow she could transmit the virus to a man with a slight irritation on his penis.

“There is a slight possibility that an infected cell could get into a man,” he said. “We think it takes more than one infected cell, but no one knows for certain.”

Experts also said it is difficult to pinpoint where the virus is transmitted. An indication as to the extent of damage to the immune system could be gained from a T-helper cell count. The T-helper cell is a white blood cell that is a critical to the body’s immune system, and a primary target of the AIDS virus. The normal range per cubic milliliter of blood is between 800 and 1,000.

Johnson is likely to be healthy for a while, AIDS physicians said. A normal procedure would be to test his immune system every three months.

When Johnson’s T-helper cells start to become depleted, doctors probably will prescribe an antiviral drug, AZT, to slow the development of full-blown AIDS.

As the virus causes further damage to Johnson’s immune system, his doctors probably will prescribe antibiotics in an attempt to prevent him from getting pneumocystis pneumonia and other infections that ultimately kill AIDS patients.

Johnson said Cookie Kelly, his wife since Sept. 14, tested negative for HIV. The tests detect antibodies to the AIDS virus, and those antibodies take at least two months to develop after a person is infected.

Johnson’s wife is likely to be tested again. If she is negative six months after the last time she had unprotected sexual intercourse with Johnson, she probably will be safe.

Johnson married Kelly, his high school sweetheart, in Lansing, Mich. According to Michigan’s premarital law, before an applicant can obtain a marriage license, the couple must file a certificate indicating they have received counseling regarding HIV infection and has been offered testing for the virus.

It is not known whether Johnson and Kelly were tested or had counseling.

Johnson’s wife is about seven weeks pregnant. If tests continue to show that she is not infected, there is virtually no chance the baby is infected, Dr. Arnold Platzker, head of neonatology at Childrens Hospital of Los Angeles, told the Associated Press. If she is infected before she delivers, there is about a 30% chance the baby will develop AIDS, he added.