Biohazards are one of the environmental stressors whose sources can be:

Animal products may be:

Biohazard agents are:

Bacteria are simple, one-celled organisms. They are not visible to the eye. Some bacteria are useful and some are harmful.

Examples for bacterial hazards are tuberculosis, tetanus, salmonellosis. 

Tuberculosis (TB): Tuberculosis, is a disease caused by a bacteria called Mycobacterium tuberculosis. The bacteria can attack any part of the body, but they usually attack the lungs.TB disease was once the leading cause of death in this country. Fortunately, in the 1940's,scientists discovered the first of several drugs now used to treat TB. As a result, TB slowly began to disappear in the United States. But TB has come back. After 1984, the number of TB cases reported in the United States began to increase.

People of all ages, all nationalities and all incomes can get tuberculosis. In 1994, more than 25,000 people in this country got TB disease. About 3,000 of these people live in New York City. TB is spread through the air from one person to another. The bacteria get into the air when a person with TB disease of the lungs or throat coughs or sneezes. People nearby may breathe in the bacteria and become infected.

Salmonellosis: Salmonellosis is caused by a bacteria called salmonella which can be found in raw meats, poultry, eggs, milk and dairy products. It is estimated that from 2 to 4 million cases of salmonellosis occur in the U.S. annually. In 1985, a salmonellosis outbreak involving 16,000 confirmed cases in 6 states was caused by low fat and whole milk from one Chicago dairy. This was the largest outbreak of foodborne salmonellosis in the U.S. FDA inspectors discovered that the pasteurization equipment had been modified to facilitate the running off of raw milk, resulting in the pasteurized milk being contaminated with raw milk under certain conditions. The dairy has subsequently disconnected the cross-linking line.

A virus is an organism that depends on a host cell for growth and reproduction and it is parasitic in nature. Hepatitis, HIV, Rabies are examples for viruses.

 A virus is not a bacterium, nor an independently-living organism. A virus cannot survive in the absence of a living cell within which to synthesize copies of itself (replicate). A virus is not strictly alive.. nor is it strictly dead... A virus has some fundamental information (genes made of DNA or RNA) which allows it to make copies of itself. However, the virus must be inside a living cell of some kind before the information can be used. In fact, the information won't be made available unless the virus enters a living cell. It is this entrance of a virus into a cell which is called a viral infection. The virus is very small relative to the size of a living cell. Therefore, the information the virus can carry is actually not enough to allow it to make copies (replicate). The virus uses the cell's machinery and some of the cell's enzymes to generate virus parts which are later assembled into thousands of new, mature, infectious virus which can leave the cell to infect other cells.

All viruses only exist to make more viruses. And with the possible exception of bacterial viruses which kill harmful bacteria, all viruses appear to be harmful because their replication leads to the death of the cell which the virus entered. A virus enters a cell by first attaching to a specific structure on the cell's surface via a specific structure on the virus surface. Depending on the virus, either the entire virus enters the cell, or perhaps only the genetic material of the virus is injected into the cell. In either case however, the ultimate result of viral infection is the exposure of virus genetic material inside the entered cell. Then, the virus material essentially "takes over" the cell and nothing but viral parts are made, which assemble into many complete viruses.

There is not a living thing identified that doesn't have some sort of susceptibility to a particular virus. Plants, animals, bacteria, whether multicellular or single-celled, can be infected with a virus specific for the organism. And, within a species, there may be 100 or more different viruses which can infect that species alone. So, whenever viruses are discussed, they are discussed as being either plant, animal or bacterial viruses - which means that an animal virus only infects a certain animal, and a plant virus only infects a particular plant. A virus is specific for a particular host if the virus infects only that host. So, there are viruses which infect only humans (smallpox), some which infect humans and one or two additional kinds of animals (influenza), some which infect only a particular kind of plant (tobacco mosaic virus), and some which infect only a particular species of bacteria (lambda bacteriophage which infects E. coli).

Humans are protected in a couple of ways. First, if a particular virus infects one or more cells of a given tissue in our body, the infection leads to the synthesis and secretion of substances called interferons. Interferons are proteins and may be designated as alpha, beta, or gamma interferon. These proteins interact with adjacent cells which help adjacent cells become more resistant to infection by the virus. Sometimes, this resistance isn't quite good enough to prevent the spread of the virus to more and more cells, and we begin to feel sick (viral infection). Then, the body's immune system takes over and begins to fight the infection by killing the virus on the outside of the cells, and kills the infected cells, too. The killing of the infected cells prevents the spread of the virus, since a virus requires a living cell in order for the virus to be able to replicate. Eventually, the virus will be completely removed, and we'll get over the illness. HIV is an exception to this situation because HIV infects cells of the immune system which are necessary to kill the infected cells.

Rabies: Rabies is a disease caused by a virus found in the saliva of infected animals and is transmitted to pets and humans by bites, or possibly by contamination of an open cut. Treatment of an infected person as critical. Untreated, rabies causes a painful death.

Most animals can be infected by the virus and can transmit the disease to man. Infected bats, raccoons, foxes, skunks, dogs or cats provide the greatest risk to humans.

The Human Immunodeficiency Virus (HIV): HIV is the virus that leads to AIDS. HIV belongs to a subset of retroviruses called lentiviruses (or slow viruses), which means that there is an interval -- sometimes years -- between the initial infection and the onset of symptoms. Upon entering the bloodstream -- through mucous membranes or blood-to-blood contact -- HIV infects the CD4+T cells and begins to replicate rapidly.

Scientists believe that when the virus enters the body, HIV begins to disable the body's immune system by using the body's aggressive immune responses to the virus to infect, replicate and kill immune system cells. Gradual deterioration of immune function and eventual destruction of lymphoid and immunologic organs is central to triggering the immunosuppression that leads to AIDS.

Hepatitis A: Hepatitis A is found in the stool of persons with hepatitis A. The virus is usually spread through person-to-person contact or through contaminated food and water. For example, you can get hepatitis A from an infected child if you don't wash your hands after changing a diaper or from an infected person if they don't wash their hands after going to the bathroom. If a contaminated cook handles food in a restaurant - the disease can spread quickly. A person can also get hepatitis A by drinking water that is contaminated with the virus or by eating food washed in contaminated water, such as raw or undercooked shellfish, salads, or unpeeled fruits.

Ninety percent of people with hepatitis B recover. In up to 10 percent of cases people infected with hepatitis B develop chronic hepatitis B and are infected for life. Chronic hepatitis can be fairly harmless, or it may be progressive and lead to cirrhosis, liver cancer, and death. Chances of developing liver cancer are 200 times higher if you are a chronic carrier. Damage to the liver cannot be reversed. People who are chronic carriers of the virus can transmit it to others. There is no cure for Hepatitis B but a vaccine is available to prevent infection.

Hepatitis C: Hepatitis C is a disease of the liver caused by a virus that was first discovered in 1989. Unlike hepatitis A which is caused by fecal contamination of food and water; or hepatitis B which is spread through contact with infected blood or other body fluids; hepatitis C is spread by direct contact with the blood of an infected person.

Prior to the discovery of the virus, it was known that some agent caused hepatitis or inflammation of the liver in people who had been given blood, and it was known that the agent could be transmitted to patients and to experimental animals in blood. In most cases, the disease is asymptomatic for years, even decades, before progressing to chronic liver disease.

It is estimated that around 4.5 million people in the United States are infected with hepatitis C, and over 200 million around the world. Hepatitis C, in combination with the less common hepatitis B, now accounts for 75% of all cases of liver disease around the world. Liver failure due to hepatitis C is the leading cause of liver transplants in the United States.

Fungi are parasitic in nature. They grow in a living host or on a dead animal. Example for fungi hazard is Histoplasmosis (Roof demolition workers and workers in barns and poultry houses are exposed to this fungus which enters the body by inhalation or ingestion)

Fungi that grow in ventilation systems may contaminate indoor environments and cause a variety of problems. Some fungi can cause lung infections. Many fungi can cause allergic reactions in susceptible people and respiratory irritation in non-allergic people. Inhalation of fungal spores by highly susceptible people can have fatal consequences. Some environmental bacteria can grow in ventilation systems, but these are rarely a threat to healthy people.

Low levels of airborne fungi can be a primary or contributing cause of Sick Building Syndrome (SBS) and poor Indoor Air Quality (IAQ).

Fungi differ significantly, in certain respects, from most other airborne pathogens, such as bacteria, viruses, and protozoa. Fungi do not cause secondary contagious infections; only the person inhaling the fungi is at risk. Fungi can exist outdoors and enter the building through the air intakes. No other respiratory pathogens can exist outdoors -- viruses and bacteria are carried and transmitted indoors by human or animal hosts, with anthrax being the one exception. Fungi are normally harmless and non-parasitic. Fungal infections inevitably result from fungi being in the wrong place, often as the result of poor cleanliness or improper design of ventilation system components.

Fungi produce spores, in much the same way as bacteria do, and this enables them to survive harsh conditions while they travel or lie dormant. Spores are usually what enter the building air intakes and what can travel through the ventilation air stream. Fungal spores are smaller than fungal cells and can vary in size from 1 micron to 100 microns. A well-maintained HEPA filter should be capable of intercepting the vast majority of fungal spores.

Filtration provides the primary defense against fungal spores entering a building ventilation system. Pre-filters can be effective against most fungi, even when in the spore form. If a higher degree of protection is required, HEPA filters can be very effective, provided they are tightly installed, and well maintained.

Fungus can grow on HEPA filters as well as other ventilation components and, if unchecked, can actually contribute to the problem.. If the fungus is already growing inside the building or ventilation system, the problem becomes somewhat more difficult. Fungi require moisture for growth. The source of the moisture must be identified and then controlled.

Cooling coils, drains pans, and water pans for humidifiers are likely locations for fungal growth, especially when there is standing water. These components should be disassembled and cleaned with a strong disinfectant, such as chlorine, when fungal or bacterial growth is found. Clogged drains are often a cause for standing water.

Condensation on ductwork or other components is another likely source of moisture. The ductwork must be inspected for fungal growth and cleaned with a disinfectant. The cause of the condensation must be identified. Often, it results from inadequate insulation, or leakage into, or out of, the ductwork. Sometimes return air can leak into the supply air duct and result in localized condensation. Sometimes the insulation itself can absorb and hold moisture, resulting in fungus growth that may then directly or indirectly produce contamination of the building air. Smoke tests, or airflow measurements, and/or pressure tests can determine duct leakage.

Most airborne fungi cause respiratory irritation and allergic reactions.

 Parasites:

They live in other animals (sometimes plants) and transmitted to humans by eating the meat or plants that are not well cooked (sushi). Examples for parasites are tape worms, liver flukes, hook worms.

Biohazards enter the body by:

Class I- No hazard or minimal hazard

Class II- Ordinary potential hazards

Class III -Special hazards (require USDA permit for importation)

Class IV -Extremely hazardous to personnel or can cause serious epidemic disease

Class V -Foreign animal pathogens that are excluded from USA by law or whose entry is restricted by USDA.

US Department of Health and Human Services, Public Health Service develop guidelines for preventing laboratory infections. 

Preventing the escape of potentially hazardous agents outside the laboratory to persons such as visitors, family members of laboratory workers, worker's who do the laundering of the laboratory clothing. 

Generally one piece, positive pressure, full body protective suits are required. Workers must pass through a chemical shower to decontaminate the suit before leaving the work area.

There are three classes of facility design:

Robotics is used in an enclosure to perform processes and analysis of the biological samples which are extremely hazardous.

Last Update: March 17, 2000