The second most frequent mode of HIV transmission is via blood and blood products.  Blood-borne transmission can be through needle-sharing during intravenous drug use, needle stick injury, transfusion of contaminated blood or blood product, or medical injections with unsterilized equipment. The risk from sharing a needle during drug injection is between and % per act, with an average of %.  The risk of acquiring HIV from a needle stick from an HIV-infected person is estimated as % (about 1 in 333) per act and the risk following mucous membrane exposure to infected blood as % (about 1 in 1000) per act.  In the United States intravenous drug users made up 12% of all new cases of HIV in 2009,  and in some areas more than 80% of people who inject drugs are HIV positive.