Transfusion-Transmitted Diseases

Viruses

Cytomegalovirus (CMV)

Cytomegalovirus (CMV) is a virus belonging to the herpes group that is rarely transmitted by blood transfusion. According to the Centers for Disease Control and Prevention (CDC), about 50 to 85 percent of adults in the United States are infected with CMV by the age of 40. CMV infection is usually mild, but it may be serious or fatal in those who are immunocompromised. Particularly at risk are low-birth weight infants and bone marrow and organ transplant patients. If a patient is at high risk of getting CMV diseases, blood that tests negative for CMV can be transfused. Alternatively, blood that has been filtered to decrease the number of white blood cells — the cells that carry CMV — will protect patients from getting a CMV infection from transfusion.

Hepatitis

Hepatitis was the first documented transfusion-transmitted disease. Many of the current practices for diminishing risk in transfusion medicine are based on the experiences of controlling the transmission of hepatitis.

Hepatitis viruses, which infect the liver, fall primarily into two groups: viruses with a chronic course that can readily be transmitted by blood transfusion (hepatitis B and C) and viruses that cause only acute disease and are rarely transmitted by transfusion (hepatitis A and E).

Hepatitis A Virus (HAV)

Hepatitis A (HAV) infection is rarely transmitted through blood transfusion; it is usually spread by contaminated food and water. About 23,000 cases are reported annually in the US, but epidemiologists estimate that the virus infects 150,000 Americans each year. Hepatitis A is very prevalent in the developing world, including Mexico and parts of the Caribbean. Because HAV antibodies are present in approximately 20 percent of the population, many with no history of hepatitis, it is assumed that many people experience unrecognized infection. There have been occasional reports in the US of transfusion-transmitted HAV, but little can be done to prevent this rare occurrence. A vaccine recently developed for HAV has replaced immune globulin as a pre-exposure prophylactic measure for people at a high risk for acquiring this infection, although the latter remains useful after exposure.

Hepatitis B Virus (HBV)

Transmission of hepatitis B virus (HBV) is rare because of routine testing of blood for the HBsAg and hepatitis B core antibody, donor screening and deferral for risk of HBV infection, and the use of only altruistic volunteer blood donors. HBV is a major cause of acute and chronic hepatitis. Each year in the US, an estimated 300,000 persons are infected with HBV. More than 10,000 patients require hospitalization, and an average of 350 die from the disease. There is an estimated pool of 750,000–1,000,000 chronically infected HBV carriers in the US. Approximately 25 percent of carriers have active hepatitis that can progress to cirrhosis of the liver. An estimated 4,000 people die each year from hepatitis B-related cirrhosis, and more than 800 die from hepatitis B-related liver cancer. The number of HBV infections in the US is falling because hepatitis B vaccinations of health care professionals and school-age children has become nearly universal.
Screening blood donors for HBV began in 1969 and became mandatory in 1972. By the mid-1970s, testing and an all-volunteer blood donor supply reduced the rate of post-transfusion hepatitis B to between 0.3 and 0.9 percent. From 1982 to 1985, an average of 3.0 percent of hepatitis B cases in the US were related to blood transfusion. During the period from 1986 to 1988, the percentage of reported cases related to blood transfusion declined to 1.0 percent, possibly as a consequence of the donor screening questions that were instituted to identify persons at increased risk for HIV infection. In 2000, the frequency of post-transfusion hepatitis B developing after a blood transfusion was estimated at perhaps 1 in 137,000 screened units of blood.

Hepatitis C Virus (HCV)

Hepatitis C, formerly known as non-A, non-B hepatitis, was discovered in the late 1980s, and all blood donations have been screened for it since 1990. Acute hepatitis C virus (HCV) is a relatively mild infection, and most people are unaware they have become infected; however, HCV becomes chronic in 80 percent of those infected. In the general population, 1.8 percent of the population has some evidence of HCV-infection. While the rate of new HCV infections is falling rapidly due to behavior changes and blood screening, HCV is an important source of serious chronic liver disease, which often develops decades after the initial exposure to the virus.

Antibody screening was started in 1990, and the test has undergone significant improvement since. In 1999, NAT testing was added in the US. After more than 10 years of testing for HCV, the risk of HCV transmission through transfusion is less than 1 per 1,000,000-screened units of blood.

HIV (Human Immunodeficiency Virus)

Transfusion transmission of HIV, the virus that causes AIDS, has been almost completely eradicated, since blood banks began interviewing donors about at-risk behaviors and a blood test became available in early 1985. The HIV antibody tests, used on every blood donation since then, have undergone continuous improvement. Starting in 1999 nucleic acid amplification testing (NAT) has been used to directly detect the genetic material of the HIV virus in blood, and current estimates are that fewer than 1 in 1,900,000 blood components is capable of transmitting HIV. Transfusion medicine specialists are continually researching new technologies to further reduce the transmission of HIV. Examples of technologies on the horizon include methods to kill viruses in donated blood (called viral inactivation) and blood component substitutes.

Human T Lymphotropic Virus I, -II (HTLV-I, -II)

HTLV-I and -II are viruses that are not related to HIV. HTLV-I is found mainly in Southwestern Japan and Caribbean islands. The viruses can cause blood or nervous system diseases in a small number of infected people (less than 5 percent lifetime risk). HTLV-II is endemic in the Americas (including the US), and also may infrequently cause slightly increased susceptibility to infections. Both of these viruses, although rare, were found in the US blood donor population in the 1980s. Few people have gotten HTLV as a result of transfusion, but because of the small transfusion risk that existed in the 1980s, tests to detect HTLV-I antibodies were developed and quickly implemented; these tests also detected many, but not all, HTLV-II infections. Tests specifically designed to detect both viruses are now available and are used by blood centers to screen every donation.

West Nile Virus (WNV)

West Nile virus (WNV) is spread by the bite of an infected mosquito. The virus can infect people, horses, many types of birds, and some other animals.

WNV was first detected in the United States in 1999 and has since been detected in many parts of the US. The first documented cases of WNV transmission through organ transplantation and transfusion were noted in 2002. The most common symptoms of transfusion-transmitted cases of WNV were fever and headache.

The preclinical incubation period is thought to range from 2 to14 days following a bite from an infected mosquito. Approximately 80% of people infected with WNV remain without symptoms, while 20% develop mild symptoms, including fever, headache, eye pain, body aches, gastrointestinal complaints, and occasionally a generalized rash or swollen lymph nodes. One in 150 to 200 persons infected with WNV develops a more severe form of the disease that may be fatal.

FDA is allowing national deployment of investigational nucleic acid tests (NAT) to screen blood for West Nile virus (WNV), until FDA-licensed tests become available. Blood centers have implemented precautionary measures to protect the blood supply from WNV, including stockpiling frozen blood components before the start of mosquito season.

Although there are limited data on the natural course of WNV infection, the deferral periods recommended are based on the longest known viremic period (the length of time a virus remains in the blood stream), with an extra safety margin added.

Who will be deferred?

• A potential donor who has been diagnosed with WNV infection (including diagnoses based on symptoms and laboratory results) will be deferred for 120 days.
• A donor whose blood or components potentially were associated with a transfusion-related WNV transmission will be deferred for 120 days from the date of the implicated donation.

Donors are encouraged to report unexplained post-donation febrile illness with headache or other symptoms suggestive of WNV infection that occur within one week after blood donation.

The following CDC Web site may be helpful: www.cdc.gov/ncidod/dvbid/westnile/city_states.htm.

Parasitic Infections

Babesiosis

Babesiosis is a parasitic infection carried by the white-footed mouse and transmitted by tick bites. It appears primarily in the northeastern US, in coastal areas that are home to the white-footed mouse. Cases also have been identified in the Upper Midwest and Pacific Northwest. About 30 transfusion-associated cases have been reported in the US. While babesiosis is often quite mild, some patients, including those without a spleen, the elderly, or the immunocompromised, may be at risk of serious illness. There are no useful tests available for screening blood donors, although testing strategies are being developed and discussed. The AABB requires that all donors be asked if they have a history of babesiosis. Those individuals with a history of the disease are permanently deferred from donating blood.

Chagas’ Disease

A Brazilian doctor, Carlos Chagas, discovered Chagas’ disease almost 100 years ago. This disease is caused by a parasite that infects as many as 18 million people worldwide. Once infection is established, it is life-long. Each year, several thousand South and Central Americans die of heart and digestive problems caused by the disease. Up to 20 percent of infected people never exhibit symptoms. This infection is rare in the US, but because of recent global population shifts, individuals from countries where this disease is common now reside in the US. To date, there have been only five cases of transfusion-transmitted Chagas’ disease reported in North America. The AABB requires that blood centers permanently prohibit blood donation from anyone who has had Chagas’ disease, and tests are being developed and screening strategies discussed.

Lyme Disease

Although transfusion-related cases have not been reported, public health agencies and the AABB are monitoring this disease because of the remote chance that it could affect transfusion safety. Lyme disease is associated with the bite of certain species of the deer tick, and can cause an illness that affects many systems within the body. Donors with a history of Lyme disease can donate, provided they have undergone a full course of antibiotic treatment and no longer have any symptoms.

Malaria

Between 1958 and 1998, the CDC recorded 103 cases of transfusion-transmitted malaria. These cases were most likely caused by donations from people who felt well and were not aware that they were carrying malaria. Although exceedingly rare in the US, malaria can cause serious consequences, including fatalities. There is no practical test available to screen donors so AABB requires blood centers to temporarily defer blood donations from people who have visited malarial areas in the past year or who emigrated from a malarial area within the past three years.

08/05

Back