Second, special laboratory tests have to be done to prove that a person has Zika virus. For example, when the virus is in a person's blood or urine, it can be found by using a special test that looks for the virus's RNA in the blood. However, the Zika virus often does not stay in the blood for very long. Also, because most people with the Zika virus have no symptoms, they do not know that they need to be tested. Blood tests that look for specific antibodies (which the body sends out to fight the Zika virus) can also be done. However, these tests are expensive and have to be done in special laboratories that do not exist everywhere. 