By exposure to tainted blood, a laboratory, or a healthcare environment Dengue can be transmitted by blood transfusion, organ transplantation, or a needle stick injury in rare cases. The virus is not destroyed by standard screening procedures used by most blood banks so it is possible for infected donors' blood to transmit the disease to recipients. Blood products are screened for viruses including Dengue before they are released by laboratories that comply with standards set by the American Red Cross and other blood agencies. These processes attempt to remove any potential contaminants that could lead to transmission of diseases such as Dengue fever after transfusion. In addition, donors are asked about symptoms of infection every time they give blood and none have reported recent travel to areas where Dengue is found. However, because there is no cure for Dengue and because patients with severe forms of the disease may need multiple blood transfusions, it is possible that undiagnosed donors could transmit the virus. As with any viral illness, individuals who have not been previously exposed to Dengue should be monitored for signs and symptoms of infection for at least 24 hours after exposure to determine if post-exposure prophylaxis is needed. If no symptoms develop, regular blood tests can be done to see if the person has antibodies against Dengue virus.