Emerging Infectious Diseases in Transfusion Medicine

Vol. 13 •Issue 10 • Page 66
Emerging Infectious Diseases in Transfusion Medicine

The blood bank community has made great strides in improving the nation’s blood supply; however, there are still viruses of concern.

The incidence of emerging infectious diseases has increased in the past two decades; the climb threatens to continue.

Although the U.S. blood supply is the safest in the world, the risk of transmission of infectious diseases by blood transfusion is still a remote possibility. Since it was discovered in 1982 that human immunodeficiency virus (HIV) could be transmitted by blood components and plasma derivatives, blood transfusions have declined in this country.

The blood supply in the United States totaled nearly 14 million units in 1997;1-3 approximately 4.5 million people receive blood or blood products annually. And while the risk of transmission of infectious diseases by blood transfusion is “as low as reasonably achievable,”2-5 the blood banking industry is still under vigorous review by Congress, the FDA, Health Resources and Services Administration (HRSA), the legal profession, media, patients and physicians.

Viruses of Concern

Many viruses—HIV, HTLV, HBV, HCV, CMV, EBV, adenovirus, rubella and measles—can directly infect leukocytes.2-12 The extent of the acquired immunodeficiency syndrome (AIDS) epidemic, for example, triggered an increase emphasis on blood safety and infectious complications of transfusion recipients.2,7

In the last two decades, the safety of the blood supply has been improved by:

1. Donor screening technique.

2. The introduction of new generation tests. The window period of detection and ability to discover new viruses in donor plasma at the earliest stage of infection are improved, thanks to high sensitivity and specificity HIV-1 P24 antigen, HCV antibody, other enzyme immunoassay (EIA) tests and nucleic acid-based molecular assays that apply nucleic acid amplification technology (NAT) such as reverse transcriptase-polymerase chain reaction (RT-PCR), PCR, nucleic acid sequence-based amplification (NASBA), branched DNA (bDNA), transcription-mediated amplification (TMA), and self-sustained sequence replication (3SR).2,11,13 The automated immunoassays and molecular diagnostic techniques have significantly decreased transfusion-associated AIDS (TAA), transfusion-associated hepatitis (TAH) and other transfusion-transmitted disease (TTD).2

3. The recent advances in pathogen reduction (PR) technology. Most PR technologies are based on various additives to blood products (RBC, plasma and platelets) that modify DNA or RNA templates and make them inaccessible to DNA or RNA polymerase.3 These technologies have been found to be effective for a wide spectrum of pathogens–viruses, bacteria, parasites and fungi–and blood products. Examples include:

•psoralen (s-59) for PR of plasma components and platelets;

•frangible anchor linker effector (FRALE, s-303) for PR of RBC;

•Inactine (PEN 110) for PR of RBC;

•riboflavin (vitamin B12) for PR of fresh frozen plasma(FRP), platelets and RBC;

•dimethylmethylene blue (DMMB) for PR of leukocytes; and

•the viral inactivation technology of solvent/detergent-treated plasma (SDP), the only FDA-licensed technique to date.3,14

Making Strides

These applications have made significant contributions to the safety of the blood supply.11,14 For example, cytomegalovirus (CMV; human herpesvirus 5, HHV-5) infection used to be a serious and life-threatening blood transfusion complication in immunocompromised patients with a severely impaired cell-mediated immunity (CMI) from bone marrow transplantation (BMT), immunosuppressive therapy or HIV/AIDS. CMV is controlled by using a PCR-based test and a regime of available prophylactic antiviral drugs (usually ganciclovir).2,10,11 Nonetheless, risk remains.4

The seronegative window period is the most important source of risk.10,11 It’s estimated that the window period for HIV is 22 days, 51 days for HTLV-I, 59 days for HBV, and 82 days for HCV.11 During the window period, recently infected individuals circulate infectious virus but have not yet developed detectable levels of viral antigen or antibody. If such infected individuals donate blood during this period, they may transmit the infection to recipients. In addition, there are no tests available for the agent of Chagas’ disease, Trypanosoma cruzi, babesiosis, Babesia microti and the yet-to-be-discovered additional hepatitis viruses.2,10,14

Viral Hepatitis

There are at least six well-described hepatitis viruses: A, B, C, D (delta), E and G.14-18 Recent studies indicate it is very likely that at least one (hepatitis F virus, HFV) or more additional hepatitis viruses exist. The viruses are readily spread; in most cases, infected individuals are asymptomatic but contagious.

Each of the hepatitis viruses infects and damages the liver, causing inflammation of the liver cells, elevated levels of bilirubin, icteric symptoms of jaundice and elevated levels of liver enzymes (ALT, AST, GGT and LDH).6,19 The hepatocellular injury is mainly the results from inflammation, cell-mediated immune responses against virus-infected cells and a direct cytopathic effect (CPE) of these viruses.20

The route of transmission, incubation period, clinical course, severity and serology of the disease differ for each virus. HAV and HEV are transmitted through oral-fecal route, especially in contaminated water; they cannot initiate a chronic infection and are not associated with primary hepatocellular carcinoma (PHC) or hepatocellular carcinoma (HCC).10

HBV, HCV, HDV and HGV are spread mainly by the exchanges of blood or body fluids and percutaneous routes.10 HDV (deltavirus) is a subviral particle that requires the co-infection of HBV for production and infection.18

HBV, HCV and HDV are the three most common causes of chronic viral hepatitis. Chronic hepatitis may progress to cirrhosis and death from liver failure. Both HBV and HCV are carcinogenic to humans and are major causes of hepatoma (PHC or HCC).12,13,18-21

As many as 90 percent of infants infected by HBV perinatally or later become chronic carriers. Twenty-five percent to 50 percent of children exposed to HBV from ages 1 to 5 years become chronically infected. Chronicity falls to 5 percent to 10 percent in older children.

The risk of persistent chronic infection among HBV infected normal, healthy adults may be even lower. The risk of developing PHC among individuals with chronic active HBV infection is 15-100 times that of non-HBV carriers.19 The World Health Organization (WHO) estimates that 80 percent of all cases of PHC can be attributed to chronic HBV infection.20

HCV (non-A, non-B hepatitis virus, NANBV), first recognized in 1989, is the most common chronic bloodborne infection and the most frequent indication for liver transplantation in the United States. It also is one of the most common important known causes of chronic liver disease worldwide.6,12,15,16,19-21 It is estimated that 1.8 percent of the American population have detectable HCV antibodies,22 and approximately 100 million people are chronic HCV carriers globally. It is an enveloped flavivirus with a positive-sense RNA genome.15

In addition to infecting hepatocytes, HCV is able to infect and replicate within peripheral blood mononuclear cells (PBMC) and some established lymphoid cell lines.11,12 It can take decades for symptoms of liver disease to appear. Most persons with chronic HCV infection might have acquired their infection 20-30 years prior as a result of receipt of blood transfusion, clotting factor concentrates prepared from plasma pools or occasional illegal drug injecting.13,16

Blood transfusions before 1992 are thought to be the most common route of HCV transmission. Studies have shown that during the 1970s and early ’80s, 20 percent of the women who had Cesarean sections were given whole-blood transfusions. As many as 250,000 American women had contracted HCV that way. About 70 percent to 85 percent of the estimated 4 million people infected in the United States fail to clear the HCV and will develop chronic liver disease with persistent viremia; 15 percent will develop cirrhosis and 5 percent will die from HCV.6,16

A close relative of HCV, HGV (or GBV-C) is a recently identified flavivirus that replicates in peripheral blood mononuclear cells (PBMC) in vitro and coinfects patients with HCV, HIV and HCV/HIV. No known disease state has been demonstrated and any clinical significance of HGV infection has yet to be established. HGV is transmitted predominantly by transfusion/parenteral routes and has high seroprevalence among transfused individuals, intravenous drug users, hemodialysis patients and transplant recipients.10


According to WHO/UNAIDS estimation, some 5 million people were infected with HIV/AIDS in 2002 and another 3.1 million died. The AIDS pandemic has killed 28 million people and infected 42 million more, most of them (approximately 30 million) in Africa.

HIV is an enveloped retrovirus (subfamily lentivirinae) that infects CD4 T-lymphocytes, dendritic cells and macrophages. The two types of HIV are closely related to each other; most AIDS worldwide is caused by the more virulent HIV-1. Group M of HIV-1 is the major group responsible for the pandemic. Group M viruses can be subdivided into at least nine clades (A to I), clade B being most prevalent in the United States and clade C being most prevalent worldwide. HIV-2, a variant of HIV-1, is prevalent in West Africa and is now spreading in India.10,11

HIV is present in blood, semen and vaginal secretions of infected people. The virus can be transmitted via transfusion of blood and blood products, needle sharing among intravenous drug abusers (IVDA), tattoo and acupuncture needles, anal and vaginal intercourse, breast milk and perinatally to newborns.7,10

HIV disease has a broad clinical spectrum ranging from asymptomatic infection, generalized lymphadenopathy and AIDS-related complex (ARC) to profound immunosuppression (absolute CD-4 cell count is less than 200 per cu. mm.) and full-blown AIDS. The diseases related to AIDS mainly consist of opportunistic infections (such as Pneumocystis carinii pneumonia, disseminated Mycobacterium avium-intracellular infection, severe CMV disease, thrush and CNS toxoplasmosis), malignancies (Kaposi’s sarcoma, CNS lymphoma, anal and cervical cancer) and AIDS-related dementia.7,10

At least 890,000 individuals are HIV infected in North America and AIDS has developed in 350,000 of them. About 2 percent of all AIDS patients in the United States were infected by blood transfusion. An additional 1 percent (mostly hemophiliacs) was infected after receiving pooled plasma products. There are slightly more than 2,000 cases of transfusion-associated AIDS in this country; the epidemic is beginning to level off due to the better strategy of donor screening.2,10

Adult T-cell leukemia/lymphoma (ATL) and Related Disorders

Human T-cell lymphotropic virus type I (HTLV-I) was the first human retrovirus to be discovered that was associated with ATL and HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP).8,10,11 HTLV-I is a type C oncogenic retrovirus that causes cancer after a long latency period of at least 20-30 years. IV drug abuse and blood transfusion are the most prominent routes of transmitting HTLV-I in the United States. U.S. blood centers began testing all blood donated for transfusion for HTLV-I antibodies since mid 1989 and the confirmed HTLV-I seropositve rate was less than 0.02 percent.

HTLV-I is transmitted in a manner similar to HIV but less effectively than HIV in whole blood transfusions. It is calculated that one unit of HTLV-I seropositive whole blood can infect 50 percent to 60 percent of recipients. By comparison, HIV infects more than 99 percent of recipients.8,9

HTLV-I is endemic in southern Japan (Kyushu and Southern Skikoku), Okinawa, the Caribbean basin, southeast United States and West Africa. ATL is a unique lymphoid neoplasia characterized by the onset in adulthood, acute course with rapid progression, skin lesions, hypercalcemia, proliferation of Sezary-like T-lymphocytes that express large quantities of IL-2 cell-membrane receptors (CD25), opportunistic infections and presence of anti-HTLV-I antibodies in most patients. The leukemic cells found in ATL express mature peripheral helper/inducer T-cell phenotype (CD2+, CD3+, CD4+, CD5+, CD7-, CD8-, CDW29+ and CD25R+). Interestingly, these leukemic cells exert strong suppressive function with respect to PWM-induced B cell differentiation in vitro.8,10,14

The neurological disorders associated with HTV-I usually are chronic in nature. TSP is a chronic, nonhereditary progressive spastic myelopathy associated with upper motor neuron lesions of the lower limbs in tropical areas (Jamaica, Colombia, Martinique). TSP in Japan (which is not tropical) is called HAM.8-11

Parvovirus B19

Parvovirus B19 is the smallest (18-26 nm) of the pathogenic DNA viruses. It was discovered in 1975 in the sera of blood donors; blood group P antigen is the cellular receptor of the virus. About 65 percent of the population is infected with B19 by 40 years of age. The virus is spread by respiratory and oral secretions as well as transplacental and transfusion. Additionally, it infects mitotically active erythroblasts in bone marrow and establishes cytolytic infection.

B19 normally causes erythema infectiosum (so-called “slapped cheek syndrome” or fifth disease) over the malar areas in children of 4 – 15 years of age. It is an acute, benign, infectious disease characterized by fever and distinctive rash on the cheeks. The rash spreads to exposed skin such as the arms and legs.

B19 infection in adults may be asymptomatic or cause polyarthritis; in a seronegative-mother, it increases the risk for fetal death (hydrops fetalis). Individuals with chronic hemolytic anemia (e.g., sickle-cell anemia, SCA) infected with B19 are at risk for a life-threatening aplastic crisis.10,14,23

There is low clinical significance of B19 infection in healthy individuals. In immunocompromized patients of leukemias, HIV/AIDS, post bone marrow transplants and hemophilias, B19 infection may persist, resulting in severe and long-lasting aplastic crisis (red cell aplasia). Symptomatic B19 infection has been reported in transfusion of plasma-derived clotting factor concentrates.24 IgM antibodies may identify recently infected and potentially still infectious individuals.

West Nile Virus (WNV)

WNV is an arthropod-borne flavivirus that belongs to the Japanese encephalitis antigenic complex (the complex also includes Japanese encephalitis, Murray Valley encephalitis, St. Louis encephalitis, etc). The small (50 nm) spheral, lipid-enveloped WNV is primarily transmitted among birds through mosquito bites; humans serve as incidental hosts.25

The emergence of WNV in the United States was first recognized in New York City in 1999; by 2002, 4,200 human cases of WNV-associated illness were reported in 44 states and Washington, DC,26 and 277 deaths of meningoencephalitis have been reported as of March 12, 2003.25

Most WNV-infected (~80 percent) individuals are asymptomatic and 20 percent of those infected will develop mild flu-like symptoms that include fever, headache, body aches, eye pain, generalized weakness, a generalized rash or swollen lymph nodes. About 0.5 percent to 0.67 percent (1 in 150-200) individuals with WNV develops severe illness of singly or in combination of encephalitis, meningitis, meningoencephalitis or acute flaccid paralysis.25 Elderly and immunocompromised persons appear to be at very high risk to develop severe WNV disease.

Pealer et al recently reported that of 61 patients identified as having possible transfusion-transmitted WNV infection, 23 were confirmed to have transfusion-associated infection.26 They concluded that transfused leukoreduced and nonleukoreduced red cells, platelets and fresh-frozen plasma can transmit WNV.26

As of July 14, 2003, every blood bank in the United States is screening donated blood for WNV, initially by minipool testing for WNV-specific IgM antibodies with the use of an IgM-capture ELISA and confirmed with a plaque-reduction neutralizing-antibody test (to distinguish among the cross-react flaviviruses) or RT-PCR.25-27 More than 601 viremic donations have been identified and removed from the blood system; some 1,000 potential recipient infections have been prevented.27

Babesiosis and Chagas’ Disease

Transfusion-transmitted parasitic infections are rarely seen in the United States; however, global changes (e.g., air travel and immigration) that have occurred in the last 40 years have contributed to a few documented cases in North America. Babesia are intracellular sporozoan parasites that morphologically resemble plasmodia. Babesiosis is a zoonosis transmitted by infected ticks (the same reservoir of Lyme disease); humans are accidental hosts.

In the United States, B. microti is the usual cause of babesiosis.14,17,28 Most infections are asymptomatic or mild, although symptoms may vary from headache, fever, nausea and vomiting and myalgia, to severe malaria-like illness with hemolysis. After an incubation period of one to four weeks, symptomatic patients experience general malaise, fever without periodicity, headache, chills, sweating, fatigue and weakness. As the infection progresses with increased destruction of erythrocytes, hemolytic anemia develops and patients may experience renal failure.

Chagas’ disease is caused by a parasitic blood and tissue protozoan, Trypanosoma cruzi. The infection may be asymptomatic, acute or chronic and is found most often among children below five years of age in Central and South America.10 About 50 percent of the infected individuals have parasitemia without clinical symptoms.

Common in children and rare in adults, the acute form is characterized by a lesion at the site of the bite, fever, weakness, enlarged spleen and lymph nodes, edema of the face and legs and tachycardia. This form resolves within four months, unless complications (encephalitis) develop. The chronic form may be manifested by cardiomyopathy or dilation of the esophagus or colon.

Some 18 million to 24 million individuals are chronic carriers. One of the earliest signs of infection is the development at the site of the bug bite of an erythematous and indurated area called a chagoma.10,17,29 About 20 percent of infected individuals develop a progressive cardiomegaly/cardiac insufficiency that is ultimately fatal.

New Variant Creutzfeldt-Jakob Disease (nvCJD)

On March 20, 1996, the British government announced there is probably a link between mad cow disease (BSE) and a new variant of the deadly human ailment, nvCJD, also known as subacute spongiform encephalopathy. Since then, 30 cases of nvCJD have been reported in the United Kingdom and one in France.

The news sparked a British beef panic; about 175,000 British cows have been infected with BSE.10,30-32 Recently, an ELISA test kit (the Enfer TSE test by Enfer Scientific, Newbridge, Ireland) for the detection of the putative infectious agent PrPsc has been approved by the European Commission.33 It is a rapid, simple, safe and sensitive test used for the postmortem detection of BSE in cattle, scrapie in sheep, and chronic wasting disease (CWD) in deer and elk.

BSE in cattles, CJD and kuru in humans, scrapie in sheep and goats, and transmissible encephalopathy in mink are progressive and invariably fatal infection of the brain caused by prions.32 Previously classified as “slow viruses,” prions are small infectious particles of 30-kd composed of proteins that infect the nervous system selectively. These are transmitted by direct exposure to infected material.

Essentially, the prion is a conformationally altered form of a normal plasma membrane protein called PrPc. The abnormal, altered form (PrPsc) is highly resistant to proteases and can form rod-shaped multimers that precipitate as amyloid. Microscopically, they all have a characteristic spongiform change in the gray matter; their similarity is emphasized by the fact that scrapie and CJD tissue cause the same disease when injected into monkeys. The spongiform alterations in the brain of CJD patients have been attributed to the deposition of PrPsc amyloid.31,32,34

The U.S. outbreak of CJD has been linked with iatrogenic transmission: brain surgery, transplantation of an infected cornea and treatment of dwarfism with growth hormone extracted from the pituitary glands of human cadavers. Since 1985, growth hormone preparations are synthesized genetically and carry no risk.31,34

On Oct. 18, 1994, the American Red Cross (ARC) reported to the FDA that a 64-year-old blood donor who donated more than 90 times had died of CJD. Plasma from his donations was often polled for further manufacture of plasma derivatives. Soon, ARC, Baxter, Miles and Sandoz began voluntary market withdrawal of implicated lots of IVIg, Factor VIII AHF, Albumin, Plasma Protein Fraction and Alpha-1-Proteinase Inhibitor. Although the evidence so far did not suggest that transfusion was a major risk factor for transmission of CJD, theoretically, CJD can be transmitted by blood and blood products.21,35

CJD (subacute spongiform encephalopathy or infectious dementia) causes rapidly progressive dementia, pronounced multifocal startle myoclonous (sudden muscular contractions) and periodic triphasic discharges on electroencephalogram (EEG). Muscular coordination diminishes, the intellect and personality deteriorate and death is usually within three to 12 months of onset.34

There is no evidence to suggest that nvCJD is transmitted by blood transfusion and the risk is unknown. However, the indirect evidence has shown that:

•Scrape may be transmitted by the intracerebral inoculation of infected buffy coat in the animal models.

•Abnormal prions are present in the lymphoid tissue of patients with nvCJD.

•B-cells may play a crucial role in the transmission of CJD to the CNS.35

Leukocyte-reduction has known important benefits to identify groups of recipients such as marrow transplant and immunocompromised/AIDS patients. To reduce the risk of transmission of nvCJD by blood transfusion, the United Kingdom and other European countries have implemented a policy of universal leukocyte-reduction of blood components and plasma for fractionation in 1998.

Dr. Shen is a consultant of laboratory medicine at the S & J Laboratories Inc., Portage, MI.

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