AIDS: The results of several recent studies have shown that HIV transmission from mother to infant is more likely to occur in situations where women have a higher level of HIV RNA in their bloodstream than in women with a smaller viral load. Four separate presentations at the 3rd Conference on Retroviruses and Opportunistic Infections in Washington, D.C., reported a relationship between viral load and maternal HIV transmission. Supported by the National Institute of Allergy and Infectious Diseases (NIAID), the Women and Infants Transmission Study (WITS) found that very low viral loads were associated with lack of transmission. A follow-up analysis of ACTG 076 found that although transmission from mother to infant was higher for women with higher HIV levels of HIV RNA, HIV transmission occurred even at low levels of RNA. Researchers at the Centers for Disease Control and Prevention (CDC) reported finding an association as well. The Aaron Diamond AIDS Research Center's study found an increasing risk of transmission in women with high virus loads. Investigators for each of the four studies found that transmission occurred in women with all ranges of viral load and cautioned against using viral load measurements when considering clinical care.