Generally, heterosexual promiscuousness has no correlation to AIDS, and itself is not a risk factor. Studies of prostitutes in Nevada brothels, which forbid anal intercourse or the use of drugs, demonstrate the absence of HIV infection or AIDS-like symptoms. However, street prostitutes in large cities, such as New York, are often found to suffer immune system damage, not from sexual promiscuity, but rather from drug usage, malnutrition, and other factors related to life on the streets. Drug usage and associated malnutrition is also the mechanism for immune system depletion among groups whose "risk factor" is often, for lack of information, mis-identified as simply "heterosexual HIV transmission". These groups include lower-income inner city populations with higher levels of drug usage, malnutrition, and other immune-damaging correlations.