No evidence of natural person-to-person transmission has been found. However, rare cases of transmission from blood transfusions have been reported. The virus which causes Colorado tick fever may stay in the blood for as long as four months after onset of the illness. Diagnosis
A combination of clinical signs, symptoms, and laboratory tests can confirm the likelihood of having CTF. Some tests include complement fixation to Colorado tick virus, immunofluorescence for Colorado tick fever, and some other common laboratory findings suggestive of CTF, including leucopenia, thrombocytopenia, and mildly elevated liver enzyme levels. Detection of viral antibodies on red blood cells is possible. Prevention
To avoid tick bites and infection, experts advise:

Avoid tick-infested areas, especially during the warmer months. Wear light-colored clothing so ticks can be easily seen. Wear a long sleeved shirt, hat, long pants, and tuck pant legs into socks. Walk in the center of trails to avoid overhanging grass and brush. Clothing and body parts should be checked every few hours for ticks when spending time outdoors in tick-infested areas. Ticks are most often found on the thigh, arms, underarms, and legs. Ticks can be very small (no bigger than a pinhead). Look carefully for new "freckles". The use of insect repellents containing DEET on skin or permethrin on clothing can be effective. Follow the directions on the container and wash off repellents when going indoors. Remove attached ticks immediately.Contracting the CTF virus is thought to provide long-lasting immunity against reinfection.
In this case, anemia may be caused by insufficient red blood cell production in addition to the hemolysis.Historically, the sucrose lysis test, in which a patients red blood cells are placed in low-ionic-strength solution and observed for hemolysis, was used for screening. If this was positive, the Hams acid hemolysis test (after Dr Thomas Ham, who described the test in 1937) was performed for confirmation. The Ham test involves placing red blood cells in mild acid; a positive result (increased RBC fragility) indicates PNH or Congenital dyserythropoietic anemia. This is now an obsolete test for diagnosing PNH due to its low sensitivity and specificity.Today, the gold standard is flow cytometry for CD55 and CD59 on white and red blood cells. Based on the levels of these cell proteins, erythrocytes may be classified as type I, II, or III PNH cells. Type I cells have normal levels of CD55 and CD59; type II have reduced levels; and type III have absent levels. The fluorescein-labeled proaerolysin (FLAER) test is being used more frequently to diagnose PNH. FLAER binds selectively to the glycophosphatidylinositol anchor and is more accurate in demonstrating a deficit than simply for CD59 or CD55. Classification
PNH is classified by the context under which it is diagnosed:
Classic PNH. Evidence of PNH in the absence of another bone marrow disorder. PNH in the setting of another specified bone marrow disorder such as aplastic anemia and myelodysplastic syndrome (MDS). Subclinical PNH. PNH abnormalities on flow cytometry without signs of hemolysis.