Young gay Latino men in Texas are testing positive for HIV in clusters, meaning that the viruses are genetically similar and the transmissions are linked. In fact, reports Texas Public Radio, the Centers for Disease Control and Prevention (CDC) has identified 16 such clusters in the state, with six in San Antonio. One of them, Cluster 51, includes 27 related cases. The state’s health department sent letters to doctors this summer alerting them of the situation and urging them to test for HIV, to consider acute HIV infection when diagnosing and to offer pre-exposure prophylaxis (PrEP). Identifying transmission clusters is important, the CDC says, because they “present opportunities for improvement of HIV health outcomes and prevention of new infections in the larger underlying risk network.”