WEDNESDAY, June 4 (HealthDay News) -- Each year, an estimated 200,000 babies worldwide are infected with the AIDS virus through their mother's breast milk. Now, a new study suggests that a short-term drug regimen could provide significant protection for infants.

"It is very practical, and these drugs are relatively cheap. We believe a large proportion [of infants] can be protected," said study co-author Dr. Taha E. Taha, co-director of the infectious disease program at Johns Hopkins University's Bloomberg School of Public Health.

The problem of HIV transmission through breast milk is especially acute in sub-Saharan Africa, where mothers rarely use formula, Taha said, while it's not a significant problem in the United States.

The estimated 200,000 infants worldwide who get AIDS annually through breast milk make up a huge portion of the 500,000 new infections. (Babies can also get HIV about 10 percent of the time during gestation when a mother is infected, Taha said.)

One solution would be to discourage breast-feeding, but a number of challenges would make it difficult to replace breast-feeding with formula in parts of Africa, Taha said. Among other hurdles, the lack of clean water would make it impossible to sanitize bottles used for formula, he said.

Assuming that breast-feeding is unlikely to decline, Taha and his colleagues tested three drug regimens designed to prevent HIV transmission through breast milk. They tested the regimens on 3,016 infants in the African country of Malawi.

One regimen, known as the control group, included a single dose of the AIDS drug nevirapine (Viramune) plus one week of treatment with the drug zidovudine (AZT or Retrovir). The other regimens added daily doses of nevirapine or nevirapine as well as zidovudine until the age of 14 weeks.

The infants who took the control-group regimen had the highest rates of HIV infection from the age of 6 weeks to 18 months. At nine months, 11 percent of the control group infants were infected with the virus, compared to 5.2 and 6.4 percent, respectively, among the nevirapine and the nevirapine-plus-zidovudine groups.

The findings were published online Wednesday in the New England Journal of Medicine and were expected to be in the July 10 print issue of the journal.

Another study in the same issue of the journal found that stopping breast-feeding early and abruptly -- as early as four months after birth -- doesn't significantly lower the risk that infants will become infected with HIV.

About two-thirds of a group of infants in the African nation of Zambia whose mothers stopped breast-feeding before five months lived without developing HIV infection to the age of 24 moths. In another group, in which mothers breast-fed for an average of 16 months, about the same percentage lived for 24 months without becoming infected with HIV.

In a commentary accompanying the two studies, a pair of AIDS specialists in South Africa praised the research. But they wrote that more studies need to look at whether HIV transmission can be prevented by both extending drug treatment and shortening the time of breast-feeding.

Still, the findings of the second study suggest that "one should not stop breast-feeding in infants whose HIV status you don't know. Stopping breast-feeding in HIV-infected infants was harmful," said Glenda Gray, one of the commentary authors and director of the Perinatal HIV Research Unit at the University of Witwatersrand in Johannesburg.

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