With the second largest population of HIV-positive people in the world, South Africa is particularly vulnerable to the deadly new strain of extremely drug-resistant tuberculosis that appears to be spreading across the country.

Authorities are attempting to seek out people she may have had contact with outside the hospital and persuade them to undergo testing.

Johannesburg is located in Gauteng, South Africa's most populous province. "Urgent steps" have been taken to contain the disease there, according to the Gauteng Department of Health. On Tuesday, health officials announced that a local company had agreed to supply one of two medicines to treat XDR TB.

XDR TB has killed 52 of 53 patients who were infected with it in the eastern South Africa province of KwaZulu-Natal, officials reported earlier this month.

So far, it has been identified in at least 28 hospitals across the country, but that may not reflect the true breadth of the disease. The lack of adequate diagnostic facilities in poor areas means that an unknown number of cases may not be recorded.

The woman whose case was confirmed in Johannesburg became critically ill in March, according to accounts, and initially was admitted to the Sizwe hospital there, but then she continued treatment as an outpatient.

The diagnosis of extremely drug-resistant TB was made only last week. In spite of the efforts of the medical staff to persuade her, she refused to be readmitted at that time.

Reportedly, she agreed to go back to the hospital on Wednesday. Now, officials are scrambling to track down other people who may have been exposed to the deadly disease.

People with AIDS are especially vulnerable to tuberculosis because their immune systems are compromised. It is the largest killer of AIDS patients in Africa, and Africa is the only continent where TB rates are on the rise. More than 5.5 million people are HIV-positive in South Africa, according to official estimates.