STIs, such as dental dams and latex gloves. Other means for preventing STIs include education on how to use condoms or other such barrier devices, testing partners before having unprotected sex, receiving regular STI screenings, to both receive treatment and prevent spreading STIs to partners, and, specifically for HIV, regularly taking prophylactic antiretroviral drugs, such as Truvada. Post-exposure prophylaxis, started within 72 hours (optimally less than 1 hour) after exposure to high-risk fluids, can also protect against HIV transmission. Malaria prevention using genetic modification Genetically modified mosquitoes are being used in developing countries to control malaria. This approach has been subject to objections and controversy. Thrombosis Thrombosis is a serious circulatory disease affecting thousands, usually older persons undergoing surgical procedures, women taking oral contraceptives and travelers. The consequences of thrombosis can be heart attacks and strokes. Prevention can include exercise, anti-embolism stockings, pneumatic devices, and pharmacological treatments. Cancer In recent years, cancer has become a global problem. Low and middle income countries share a majority of the cancer burden largely due to exposure to carcinogens resulting from industrialization and globalization. However, primary prevention of cancer and knowledge of cancer risk factors can reduce over one third of all cancer cases. Primary prevention of cancer can also prevent other diseases, both communicable and non-communicable, that share common risk factors with cancer. Lung cancer Lung cancer is the leading cause of cancer-related deaths in the United States and Europe and is a major cause of death in other countries. Tobacco is an environmental carcinogen and the major underlying cause of lung cancer. Between 25% and 40% of all cancer deaths and about 90% of lung cancer cases are associated with tobacco use. Other carcinogens include asbestos and radioactive materials. Both smoking and second-hand exposure from other smokers can lead to lung cancer and eventually death. Prevention of tobacco use is paramount to prevention of lung cancer. Individual, community, and statewide interventions can prevent or cease tobacco use. 90% of adults in the U.S. who have ever smoked did so prior to the age of 20. In-school prevention/educational programs, as well as counseling resources, can help prevent and cease adolescent smoking. Other cessation techniques include group support programs, nicotine replacement therapy (NRT), hypnosis, and self-motivated behavioral change. Studies have shown long term success rates (>1 year) of 20% for hypnosis and 10%-20% for group therapy. Cancer screening programs serve as effective sources of