Risks of Blood-Borne Disease

1

What infectious diseases are transmissible via blood transfusion?

Over 100 million blood donations are collected annually worldwide. Approximately half of these are collected in developed countries. Viruses, parasites, and bacteria and the diseases they transmit have all been found in donated blood. HBV, HCV, HIV 1 and 2, HTLV1 and 2, CMV, Parvovirus B19, Dengue virus, West Nile virus, trypanosomiasis, malaria, and variant Creutzfeldt-Jakob disease can all be transmitted in transfused blood. The most commonly transmitted diseases in developed nations include hepatitis B virus (HBV) and hepatitis C virus (HCV); human immunodeficiency virus (HIV) and cytomegalovirus (CMV) transmission are far less common. Parasites such as malaria (Plasmodium), Chagas’ disease (Trypanosoma cruzi), toxoplasmosis (Toxoplasma gondii), and babesiosis (Babesia) are only a problem where these diseases are endemic. Lymphomas and leukemias can be caused by human T-cell lymphotropic virus (HTLV-1) and infectious mononucleosis by Epstein-Barr virus (EBV). Viruses such as West Nile were also transmitted prior to instituting testing. The Zika virus is currently under investigation. Bacterial contamination of blood products occurs most often in platelets, which are stored at room temperature. Bacterial contamination can result in sepsis or a toxic shock-like syndrome, or in transmission of syphilis (treponema pallidum).

Donor screening has nearly eliminated blood-transfusion-transmitted HIV, HTLV, and the hepatitides. However, infection remains a significant risk in less-developed countries, where millions of units of blood are not screened for transmissible pathogens. To date, 25 countries are still not able to screen blood for HIV, HBV, HCV, and syphilis according to WHO recommendations.

2

What are the estimated risks of HBV, HCV, and HIV transmission by blood transfusion in the United States?

Rates of viral disease transmission are lower than ever, particularly after nucleic acid testing for HIV, HBV, and HCV began in 1999. At present, mathematical models are employed to estimate risks of viral transmission in developed countries because the rates are so low.

3

Which blood-borne pathogens pose a risk to surgeons?

HIV, HBV, and HCV are diseases of concern to surgeons because of the morbidity and mortality associated with these diseases. There has never been a confirmed case of HIV infection from occupational exposure in a surgeon. As of 2003 (the most recent data available in 2008), only 58 confirmed cases of healthcare-worker HIV infection by patients have been reported, including six physicians (all nonsurgeons). In all cases, the inciting injury involved significant cuts or penetration with large-bore hollow needles, never with solid needlesticks. The hepatitides do remain threats. HBV infection of surgeons has declined with the widespread use of the HBV vaccine (see below). A hollow needlestick can result in HBV transmission in as many as 30% of cases. The risk of HCV in the operating room remains significant because the number of chronically infected patients numbers––2.7 million to 3.9 million in the United States alone.

4

What is the risk to healthcare workers of exposure to hepatitis B virus?

Of the 35 million healthcare workers globally, approximately 3 million are exposed percutaneously to blood-borne pathogens every year. This includes 2 million exposures to HBV, 900,000 to HCV, and 170,000 to HIV. More than 90% of documented transmissions are in developing countries. Millions of healthcare workers are exposed to blood or other body fluids annually. Eighty-two percent are exposed through percutaneous injury such as needlesticks, and another 14% through contact with the mucosal membranes of the eyes, mouth, or nose.

Blood, cerebrospinal fluid, synovial fluid, pleural fluid, peritoneal fluid, pericardial fluid, and amniotic fluid all carry a risk for transmitting HBV. Sputum, urine, and vomitus are not considered to be infectious unless they contain blood. HBV is highly infectious and can remain infectious on environmental surfaces for at least 7 days.

Hepatitis B e antigen (HBeAg)––a degradation product of the viral nucleocapsid that represents active replication in the liver—is the marker for HBV replication and viral load. In studies of healthcare personnel who sustained injuries from needles contaminated with HBV, 37%–62% developed serologic evidence of HBV and 22%–31% developed clinical hepatitis. However, if the exposure was to HBsAg-positive, HBeAg-negative blood the risk for serologic evidence of HBV infection was 23%–37%, and 1%–6% will develop clinical hepatitis. Thirty percent of acute HBV cases are clinically occult, and 5% remain chronic carriers for life. About 25% of people with chronic HBV eventually die of hepatic disease.

In the United States, the incidence of HBV has declined sharply over the last 15 years, mainly because of effective vaccination strategies. In 2013 the CDC estimated just fewer than 20,000 new cases. In 2014 the CDC estimated 850,000 persons with chronic HBV in the United States.

5

What is the risk to healthcare workers of exposure to hepatitis C virus (HCV)?

HCV is transmitted via blood, and patients at higher risk include injection drug users, patients who received a blood transfusion before 1999, hemophiliacs, patients on hemodialysis, and healthcare workers. Acute HCV infection is asymptomatic in 70% of cases. Approximately 1.8% of needlesticks or sharps exposures result in HCV infection, but one study indicated that only exposure with hollow-bore needles was associated with transmission. After exposure, the rate of seroconversion to HCV is approximately 10%. Fifty percent to 80% of seroconverters develop a persistent chronic HCV infection, and 20% of these advance to hepatic cirrhosis. Recent years have seen the development of new and promising treatment for hepatitis C with a high cure rate; however, success depends on the genotype of the virus and treatments are very expensive.

6

What is the risk to healthcare workers of exposure to HIV?

Among healthcare workers only 58 confirmed cases and fewer than 150 “possible” cases (unconfirmed as a result of poor documentation) of HIV transmission have occurred since 1983. The majority of confirmed cases were nurses (n = 24), while six were physicians. None were surgeons. Eighty-four percent of the affected individuals suffered percutaneous routes of transmission—that is, cuts or punctures. The risk of seroconversion to HIV after a percutaneous exposure is 0.3%. After exposure via mucous membrane, the risk of conversion is 0.09%. Since 1999, only one confirmed case of occupationally acquired HIV infection has been reported to the CDC, a lab technician who sustained a needlestick while working with live HIV cultures in 2008.