Biohazards

Natural Pathogens and Diseases

Pathogens such as microscopic bacteria, viruses, and parasites are biohazards that can result in infectious disease pandemics and foodborne and waterborne illnesses that claim millions of lives each year. These biohazards are spread through a variety of methods, including contact with domesticated and wild animals; insect bites; contaminated food, water, or blood; and through the air. Well-known historic pandemics included the Black Plague, caused by the Yersinia pestis bacterium in the 14th century; the transmission of smallpox and other European diseases that decimated the indigenous populations of the New World in the late 15th through the 18th centuries; and the influenza A H1N1, or Spanish flu, outbreak that spread globally in 1918 in part due to the return of soldiers after World War I.

Older diseases continued to spread in the modern era, including the avian influenza H5N1 (bird flu), the influenza A H1N1 (swine flu), tuberculosis, hepatitis, malaria, West Nile virus, and dengue fever. New diseases and strains have also emerged, including severe acute respiratory syndrome (SARS), Ebola, and Hantavirus. New drug-resistant strains, such as the methicillin-resistant Staphylococcus aureus bacterium, and drug-resistant tuberculosis have presented new challenges in medical treatment.

HIV/AIDS spread globally through unprotected sexual intercourse, illegal blood donations, inadequate blood donor screening, improper handling and disposal of medical waste, and the sharing or reusing of needles. HIV/AIDS claimed over 2 million lives globally in 2007, most in African countries, and left behind a growing population of AIDS orphans. Rates of sexually transmitted diseases have also remained high. According to 2004 World Health Organization statistics, there were 18.4 million global deaths due to communicable diseases.

Foodborne and waterborne illnesses annually sicken, malnourish, impair, or kill millions more worldwide. Bacteria such as Salmonella, Campylobacter, Listeria, and Escherichia coli (E. coli), as well as viruses such as the norovirus (Norwalk virus), cause periodic outbreaks of food poisoning. Contamination also results in recalls of associated products, causing large financial losses to agricultural producers, governments, corporations, grocery stores, and restaurants. A 1990s outbreak of bovine spongiform encephalopathy, commonly known as “mad cow disease,” in Great Britain led to a search for its origin in infected feed, international bans on the importation of British beef, and fears of the spread of the disease's human variant, Creutzfeldt-Jakob disease.

Diseases spread through skin contact with, or ingestion or use of, contaminated water include cholera, caused by the Vibrio cholerae bacterium; typhoid fever, caused by the Salmonella typhi bacterium; and schistosomiasis, caused by the Schistosoma parasite. Water chlorination and improved sanitation have led to drastic reductions in water-borne illnesses in developed countries, but billions of people in developing countries still lack access to safe water and basic sanitary conditions. The dumping of raw sewage and medical wastes into waterways is another major source of contamination that results in waterborne illness.

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