A former counselor at Ballou Senior High School was infected with the AIDS virus at the time he sexually abused a student, a prosecutor disclosed in court yesterday.

The revelation came at the sentencing of John T. Jones, 39, who was convicted in June of misdemeanor sexual abuse and assault charges stemming from incidents that took place from 2001 to 2003.

Jones, who was attendance chief at the Southeast Washington school, apparently told authorities of his condition last month, before he was originally scheduled to be sentenced in D.C. Superior Court.

The news sent the victim, now 18, into hysteria, Assistant U.S. Attorney Cynthia G. Wright told the court, reading from a letter the girl had written soon after learning of Jones's condition.

"Right now, I'm very upset because I found out that he may be HIV-positive," the teenager, who attended the sentencing, wrote in the letter. "I may be HIV-positive, too. I will be frustrated all the time, scared to die. I felt OK until today. Now I'm upset and scared."

The teenager has tested negative for the virus and, based on the time since the sexual encounters, doctors consider her uninfected, said Wright, the prosecutor in the case. Precisely when Jones learned that he was carrying the human immunodeficiency virus did not emerge in court, but Wright expressed outrage that Jones had put the girl at such risk. She urged that he get the maximum sentence.

Calling Jones's conduct a "colossal breach of trust," Judge Ann O'Regan Keary sentenced him to about five years in prison -- the maximum -- and ordered him to register as a sex offender when he is released.

"I find no conceivable reason for leniency here," the judge said.

Defense lawyers for Jones said that he maintains that he is innocent and sought to prevent his medical status from being discussed in open court. The judge allowed prosecutors to introduce the information.

Joanna Day, of the D.C. Public Defender Service, argued that Jones should be sentenced to only the 16 months he already had spent behind bars. Jones, she said, is devoted to his family, and the time in jail has been a severe punishment.

Jones declined to address the court at his sentencing.

Wright and co-counsel Geoffrey A. Barrow had charged that, over a period of about three years, Jones used his position of authority to try to extract sex from at least three girls at the school.

An alumnus of Ballou and a friend of the principal at the time, Jones would threaten to change the girls' grades and to report them as absent if they resisted his advances, prosecutors said.

But many of the encounters were not reported immediately. Police did not become aware of the allegations until 2003 -- a time lag that was among the factors that complicated the prosecution.

After the trial, the jury forewoman said in an interview that the jurors were certain that Jones had assaulted the main accuser but were not certain that the events took place before the girl turned 16 -- a key legal threshold in sex cases.

While jurors may have had difficulty reaching a verdict, Keary appeared to have little such trouble making up his mind. The judge said that, in convicting Jones of misdemeanors, the jury had afforded him leniency.

The jury convicted Jones of assaulting a second girl but acquitted him of sexually enticing her. The jury also acquitted Jones of assaulting a third Ballou student.

The first trial on the charges ended in March with acquittals on several counts and a hung jury on the others. In the retrial that ended in June, the jury acquitted Jones of several of the 15 remaining charges but found him guilty of seven counts of sexual abuse and one count of simple assault.

Seven years earlier, Jones was tried on charges that he raped a 15-year-old girl. The jury in that case could not reach a verdict, and prosecutors did not retry the case.