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Biological Hazards

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Biological Agents and Toxins

Many laboratory workers encounter daily exposure to biological hazards. These hazards are present in various sources throughout the laboratory such as blood and body fluids, culture specimens, body tissue and cadavers, and laboratory animals, as well as other workers.

Harmful biological agents are generally divided into either infectious agents or non-infectious agents.

  • Infectious agents are pathogenic bacteria, viruses, and fungi
  • Non-infectious agents are called "toxins" and are produced from infectious agents and other living organisms and plants.

Certain biological agents (e.g., viruses, bacteria, fungi, and prions) and toxins have the potential to pose a severe threat to public, animal or plant health, or to animal or plant products. These biological agents and toxins are referred to by the CDC and USDA as "select agents and toxins." Common examples of select infectious agents and non-infectious toxins include:

More information about select agents and toxins can be found at the CDC Federal Select Agent Program Page and OSHA's Biological Agents Topics Page.

1. Which of the following is considered a non-infectious agent?

a. Bacillus anthracis
b. Ebola virus
c. Ricin toxin
d. Variola virus

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CDC BSLs 1-2. (Click to enlarge)

Anthrax is an acute infectious disease caused by a spore-forming bacterium called Bacillus Anthracis. It is generally acquired following contact with anthrax-infected animals or anthrax-contaminated animal products. Anthrax is receiving heightened attention because of its use as a biological warfare agent.

Laboratory Incident

The CDC and NIH established four biosafety levels of control to contain biological agents and toxins. The levels are based on the operations to be performed, known or suspected routes of entry and transmission, and laboratory function.

In 2014, one of CDC's biosafety level 3 (BSL-3) laboratories was preparing anthrax samples to be sent for research at two CDC labs with lower biosafety levels, both of them BSL-2 labs. The procedure used in the BSL-3 lab may not have fully inactivated the samples.

CDC BSLs 3-4. (Click to enlarge)

The two BSL-2 labs where the samples were sent were not equipped to handle live anthrax bacteria. Workers in the BSL-2 labs, believing the samples were inactivated, were not wearing adequate personal protective equipment needed to work with live bacteria while handling the material. Procedures used in two of the three involved labs also may have aerosolized the anthrax spores (put them into the air).

CDC immediately began investigating the incident to assess the health risk to staff. All work in the affected labs was suspended for decontamination. CDC notified potentially exposed personnel as soon as they were identified and referred them to the CDC health clinic or to a local emergency department for evaluation and preventive care. Potentially exposed staff were offered antibiotics and vaccinations to prevent possible anthrax infection. No staff had shown symptoms of anthrax or tested positive for anthrax infection.

CDC also performed environmental testing of the affected labs before they were decontaminated; preliminary results for some of the tests were negative for anthrax, suggesting that contamination or release was unlikely. (Source CDC)

2. Anthrax is receiving heightened attention because _____.

a. multiple strains of the virus have been discovered
b. new cases of anthrax have occurred in Africa
c. of its use as a biological warfare agent
d. it has mutated into a "superbug"

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Risk Reduction Matrix

Hierarchy of Control
OSHA's Risk Reduction Matrix
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To help employers determine appropriate work practices and precautions, OSHA has divided workplaces and work operations into three risk zones, according to the likelihood of contamination with anthrax spores and employee exposure to them. These zones are called the green zone, the yellow zone, and the red zone.

  • Green Zone: workplaces where contamination with anthrax spores is unlikely.
  • Yellow Zone: workplaces where contamination with anthrax spores is possible.
  • Red Zone: workplaces where public health or law enforcement authorities have stated that contamination with anthrax spores has been confirmed or is strongly suspected.

We show these zones within the shape of a pyramid to represent how the risk appears to be distributed. Based on information currently available, contamination with anthrax spores and exposure to the bacterium are unlikely in the vast majority of American workplaces, represented by the green zone.

Making Informed Decisions

This matrix is intended to help employers understand how to assess the risk of exposure to anthrax spores in their workplaces and to make the necessary decisions to successfully protect their workers from this exposure. The level of risk in any particular workplace is based upon factors such as:

  • current patterns of workplaces contaminated with anthrax spores;
  • the likelihood of the workplace being a target for Bacillus Anthracis contamination;
  • the proximity of a workplace or workstation to areas known to be contaminated with anthrax spores;
  • the likelihood of the workplace receiving mail or other items from a contaminated facility;
  • any information provided by law enforcement or public health officials about the workplace's risk of receiving contaminated items;
  • the amount of mail the workplace receives;
  • the type of workplace (for example, a post office, bulk mail center, or public or private mail room where cross-contamination might be possible);
  • the potential that workplace operations and tasks could result in exposure if contaminated mail is received;
  • the use of high speed mail handling equipment, or other processes that might aerosolize anthrax spores during processing; or
  • any other information or analysis that would indicate the workplace might be contaminated with anthrax spores.

Visit OSHA's Anthrax Webpage for more information.

3. In OSHA's risk reduction matrix, which zone signifies workplaces where contamination with anthrax spores is possible?

a. Blue
b. Green
c. Yellow
d. Red

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Avian Flu

Avian Flu
Avian influenza is caused by influenza type A viruses that normally only occur in birds.

Avian influenza, commonly known as "avian flu" or "bird flu," is caused by influenza type A viruses that normally only occur in birds. Wild birds, particularly waterfowl, are natural hosts of avian flu viruses and often show no symptoms; however, some of the viruses can cause high mortality in poultry, including the H5N1 virus. Some strains of avian flu viruses carried by these wild birds can infect domestic fowl and, in turn, can infect humans, causing fever, cough, sore throat, eye infections and muscle pain.

Avian flu can also lead to pneumonia, acute respiratory distress, and other severe and life-threatening complications. The most common route of transmission to humans is by contact with contaminated poultry.

Transmission to Humans

Exposure of the conjunctival membranes of the eyes and/or the oral or nasal mucosa to secretions (oral, nasal or fecal) from AI-infected birds is the predominant route of transmission of these viruses to humans.

Avoid direct contact with bird secretions and inhalation of dust contaminated with these secretions.

There are several subtypes of avian influenza A viruses. The subtype that has become of major concern is avian influenza A (pN1) virus which has caused the deaths of millions of birds and also poses a health risk to humans.

Basic Infection Control Measures for Laboratory Employees

Asian highly pathogenic avian influenza (HPAI) A(H5N1) virus is classified as a select agent and must be worked with under Biosafety Level (BSL) 3 with enhancements. These conditions include BSL 3 procedures, plus the following:

  • controlled access, double-door entry with change room and shower;
  • use of showers by personnel before exiting;
  • decontamination of all wastes; and
  • use of at least an N-95 respirator.

Personnel should not eat, drink, or smoke or use bathroom facilities while engaged in activities where contact with contaminated animals or surfaces are possible. PPE should be properly removed and discarded or disinfected. Hands should then be washed thoroughly before eating, drinking, smoking or bathroom use.

For more information, see OSHA Publication 3323-10N 2006, Protecting Employees from Avian Flu (Avian Influenza) Viruses.

4. Working with Asian highly pathogenic avian influenza (HPAI) A(H5N1) virus in the laboratory requires _____.

a. BSL Level 1 with additional procedures
b. BSL Level 2 special monitoring
c. BSL Level 3 with enhanced procedures
d. BSL Level 4 standard procedures

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Clostridium botulinum and Botulism
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Cases of botulism are usually associated with consumption of preserved foods. However, botulinum toxins are currently among the most common compounds explored by terrorists for use as biological weapons. Botulinum neurotoxins, the causative agents of botulism, are HHS/CDC select agents.

In the United States an average of 110 cases of botulism are reported each year. Botulism is a muscle-paralyzing disease caused by a toxin made by a bacterium called Clostridium Botulinum. Botulinum toxins are some of the most poisonous substances known. Miniscule quantities are capable of producing disease in humans.

Foodborne Disease

Foodborne illnesses are caused by viruses, bacteria, parasites, toxins, metals, and prions (microscopic protein particles). Symptoms range from mild gastroenteritis to life-threatening neurologic, hepatic and renal syndromes.

Foodborne Disease
Foodborne illnesses are contracted from eating contaminated food or beverages.

They are contracted from eating contaminated food or beverages. Illnesses include foodborne intoxications and infections, which are often incorrectly referred to as food poisoning. There are more than 250 different foodborne diseases including: Botulism, Brucellosis, Campylobacter enteritis, Escherichia coli, Hepatitis A, Listeriosis, Salmonellosis, Shigellosis, Toxoplasmosis, Viral gastroenteritis, Taeniasis and Trichinosis.

The quality of food, and controls used to prevent foodborne diseases, are primarily regulated by the US Food and Drug Administration (FDA), the Centers for Disease Control and Prevention (CDC), and local public health authorities. These diseases may be occupationally related if they affect the food processors (e.g., poultry processing workers), food preparers and servers (e.g., cooks, waiters), or workers who are provided food at the worksite. Foodborne disease is addressed in specific standards for the general and construction industries.

For more information on foodborne disease see OSHA’s Foodborne Disease topics page.

5. Which of the following is one of the most poisonous toxins known today?

b. Ebola
c. Botulinum
d. Variola

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Preventing Hantavirus Disease - CDC

Hantaviruses are transmitted to humans from the dried droppings, urine, or saliva of mice and rats. The disease begins as a flu-like illness characterized by fever, chills, and muscle aches, but it can rapidly progress to a life-threatening condition marked by respiratory failure as the lungs fill with fluid.

Animal laboratory workers and persons working in infested buildings are at increased risk to this disease, particularly during dusty clean-up activities. Infection with hantavirus can progress to Hantavirus Pulmonary Syndrome (HPS), which can be fatal.

There are several other ways rodents may spread hantavirus to people:

  • If a rodent with the virus bites someone, the virus may be spread to that person, but this type of transmission is rare.
  • Researchers believe that people may be able to get the virus if they touch something that has been contaminated with rodent urine, droppings, or saliva, and then touch their nose or mouth.
  • Researchers also suspect people can become sick if they eat food contaminated by urine, droppings, or saliva from an infected rodent.

For more information on Hanta Virus see the CDC home page on Hantavirus.

Legionnaires’ Disease

Legionnaires’ Disease
More than 43 species of Legionella have been identified and more than 20 linked with human diseases.

Legionnaires' disease is a common name for one of the several illnesses caused by Legionnaires' disease bacteria (LDB). Legionnaires' disease is an infection of the lungs and is a form of pneumonia. More than 43 species of Legionella have been identified and more than 20 linked with human diseases. Legionellosis is the term for the diseases produced by LDB. In addition to Legionnaires' disease, the same bacteria also causes a flu-like disease called Pontiac fever.

Legionnaires' disease sources may include almost any warm water system or device, including man-made or natural, that disseminates water, particularly as aerosols, sprays or mists, and provides favorable conditions for LDB growth and amplification.

Disease transmission is most likely to occur via:

  • Inhalation of aerosols, fine sprays, mists or other microscopic droplets of water contaminated with LDB, providing direct access into the lungs.
  • Aspiration such as may occur when choking or spontaneously during the drinking, ingesting, or swallowing process. This allows oral fluids and particles to by-pass natural gag reflexes and enter into the respiratory tract and lungs instead of the esophagus and stomach.
  • There is no evidence that the diseases are transmitted from one person to another.

For more information on Legionnaires' disease, see OSHA's Legionnaires' Disease Webpage.

6. Which of the following are transmitted to humans from the dried droppings, urine, or saliva of mice and rats?

a. Hantaviruses
b. Anthrax
c. Ebola
d. Legionnaires' Disease

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Molds and Fungi

Molds and Fungi
Molds are fungi that are found everywhere—both indoors and outdoors all year round.

Molds are fungi that are found everywhere—both indoors and outdoors all year round. The terms fungi and mold are often used interchangeably, but mold is actually a type of fungi. Concern about indoor exposure to mold has increased along with public awareness that exposure to mold can cause a variety of adverse health effects.

There are many thousands of species of mold and most if not all of the mold found indoors comes from outdoor sources. It seems likely to grow and become a problem only when there is water damage, high humidity, or dampness.

Molds produce and release millions of spores small enough to be air-, water-, or insect-borne. They can also produce toxic agents known as mycotoxins. Spores and mycotoxins can have negative effects on human health.

For those laboratory employees who are affected by mold exposures there can be a wide variation in how they react. Employees at greatest risk of health effects are individuals with allergies, asthma, sinusitis, or other respiratory conditions and weakened immune systems.

For more information on molds, read OSHA’s publication 3304-04N 2006, Preventing Mold-Related Problems in the Indoor Workplace.


Throughout history, plague has claimed the lives of millions throughout the world.

Plague is a disease well-known to humankind. Throughout history, in a series of epidemics, plague has claimed the lives of millions throughout the world. Infective fleabites are the most common mode of transmission, but direct human contact with infected tissues or body fluids of animals and humans also may serve as sources of infection. Human plague in the United States occurs as mostly scattered cases in rural areas effecting 10 to 20 persons each year. Globally, the World Health Organization (WHO) reports 1,000 to 3,000 cases every year.

Yersinia pestis, a documented laboratory hazard, is the causative agent of plague. It is a gram-negative, microaerophilic coccobacillus frequently characterized by a "safety pin" appearance on stained preparations from specimens. Specific biosafety procedures, including PPE, engineering controls, and additional work practices have been established for handling plague bacteria in laboratories.

Laboratory and field personnel should be counseled on methods to avoid fleabites and accidental autoinoculation when handling potentially infected live or dead animals. Special care should be taken to avoid generating aerosols or airborne droplets while handling infectious materials or when performing necropsies on naturally or experimentally infected animals. Gloves should be worn when handling potentially infectious materials including field or laboratory infected animals.

For more information on Plague, see OSHA's Plague Webpage.

7. Employees at greatest risk of health effects are individuals with _____, or other respiratory conditions and weakened immune systems.

a. allergies, asthma, sinusitis
b. viruses
c. infectious bacteria
d. a cold

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Ricin Toxin

Ricin Toxin
Ricin is one of the most toxic and easily produced plant toxins.

Ricin is one of the most toxic and easily produced plant toxins. Ricin is produced in maturing seeds of the castor bean, Ricinus communis, which has been recognized for centuries as a highly poisonous plant for humans and livestock. Ricin belongs to a family of ribosome inactivating proteins from plants, including abrin, modeccin, and viscumin, that share a similar overall structure and mechanism of action.

Gastric ingestion of ricin causes nausea, vomiting, diarrhea, abdominal cramps and dehydration. Initial symptoms may appear more rapidly following gastric ingestion (1-5 h), but generally require exposure to much higher levels of toxin compared with the inhalation route.

Ricin is a relatively non-specific cytotoxin and irritant that should be handled in the laboratory as a non-volatile toxic chemical. A BSC (Class II, Type B1 or B2) or a chemical fume hood equipped with an exhaust HEPA filter and charcoal filter are indicated for activities with a high potential for aerosol, such as powder samples, and the use of large quantities of toxin. Laboratory coat, gloves, and full-face respirator should be worn if there is a potential for creating a toxin aerosol.

For more information on Ricin, see OSHA's Ricin Webpage.

Severe Acute Respiratory Syndrome (SARS)

Severe Acute Respiratory Syndrome (SARS)
SARS is a severe viral illness that was first reported in Asia in February 2003.

SARS is a severe viral illness that was first reported in Asia in February 2003. The illness is characterized by a variety of symptoms including fever, cough, and shortness of breath. In a minority of patients (6-9%), SARS may even progress to death. SARS has been reported in North America among persons returning from travel to Asia, among health care workers, and among others in contact with individuals with SARS. Because new outbreaks may occur, laboratory employees should be aware of the recommended measures to prevent occupational SARS infection.

SARS is spread primarily by close contact with a SARS patient or contact with respiratory secretions/body fluids from a SARS patient. Transmission from contaminated objects has been reported. The incubation period is typically between two and seven days.

SARS presentation is typical of a respiratory viral illness. Patients usually present with a high fever (>100.4 F), cough, chills and headache. Most will progress to develop pneumonia and some will even require mechanical ventilation.

Work procedures to prevent the spread of disease include frequent hand cleansing and avoiding direct contact with body fluids of SARS patients. Personal protective equipment (PPE) is appropriate in healthcare facilities and certain occupational settings, such as airline clean-up, when SARS infection is a known risk. Staff should not sort soiled linens suspected of SARS contamination at the point of use. Laundering soiled linens in warm water and detergent has been advised. Compressed air should not be used for cleaning areas where SARS patients or their body fluids are present.

Engineering Controls include use of airborne isolation rooms or negative air pressure environments for aerosol generating procedures (e.g. sputum induction in SARS patients) and handling laboratory specimens in biological safety cabinets.

For more information on SARS-CoV-2( causes COVID-19) see OSHA's Coronavirus Disease (COVID-19) website.

8. Work procedures, including frequent hand cleansing and avoiding direct contact with body fluids of patients, should be used to prevent the spread of _____.

b. Ricin
c. Molds
d. Plague

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(Click to enlarge)

Smallpox is a highly contagious disease unique to humans. It is estimated that no more than 20 percent of the population has any immunity from previous vaccination. Smallpox outbreaks have occurred from time to time for thousands of years, but in 1980 the disease was declared eradicated following worldwide vaccination programs. Except for stockpiles in high-security laboratories, the virus has been eliminated. However, if obtained and deliberately released as a bioweapon, smallpox could cause a public health catastrophe.

Generally, direct and fairly prolonged face-to-face contact is required to spread smallpox from one person to another. Smallpox also can be spread through direct contact with infected bodily fluids or contaminated objects such as bedding or clothing. Rarely, smallpox has been spread by virus carried in the air in enclosed settings such as buildings, buses, and trains. Humans are the only natural hosts of variola. Smallpox is not known to be transmitted by insects or animals.

A person with smallpox is sometimes contagious with onset of fever (prodrome phase), but the person becomes most contagious with the onset of rash. At this stage the infected person is usually very sick and not able to move around in the community. The infected person is contagious until the last smallpox scab falls off.

Vaccination within 3 days of exposure will completely prevent or significantly modify smallpox in the vast majority of people. Vaccination 4 to 7 days after exposure likely offers some protection from disease or may modify the severity of disease.

For more information on Smallpox, see OSHA's Smallpox Webpage.

9. Which of the following has been eradicated but could cause a public-health catastrophe if deliberately released as a bioweapon?

a. Botulism
b. Ebola
c. Tularemia
d. Smallpox

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Humans can become infected with tularemia through several routes.

Tularemia is a disease of animals and humans caused by the bacterium Francisella tularensis. Rabbits, hares, and rodents are especially susceptible and often die in large numbers during outbreaks. Humans can become infected through several routes, including:

  • Tick and deer fly bites
  • Skin contact with infected animals
  • Ingestion of contaminated water
  • Laboratory exposure
  • Inhalation of contaminated dusts or aerosols

Symptoms vary depending upon the route of infection. Although tularemia can be life-threatening, most infections can be treated successfully with antibiotics.

Steps to prevent tularemia include:

  • Use of insect repellent
  • Wearing gloves when handling sick or dead animals
  • Avoiding mowing over dead animals

Francisella tularensis is highly infectious when grown in culture, and laboratory-acquired infections have been documented. The isolation of F. tularensis from clinical specimens, especially if unanticipated, can generate concern among laboratory workers about possible exposure.

For more information on Tularemia, see OSHA's Tularemia Webpage.

10. Which of the following is highly infectious when grown in culture, and have caused laboratory-acquired infections?

a. Ebola virus
b. Francisella tularensis
c. Hemorrhagic fever virus
d. Legionnaires' disease bacteria (LDB)

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Ebola and Viral Hemorrhagic Fevers (VHFs)

Ebola and Viral Hemorrhagic Fevers (VHFs)
Ebola virus disease is a severe disease that causes hemorrhagic fever in humans and animals.

Ebola virus disease (EVD) is a severe disease that causes hemorrhagic fever in humans and animals. Diseases that cause hemorrhagic fevers, such as Ebola, are often fatal as they affect the body's vascular system (how blood moves through the body). This can lead to significant internal bleeding and organ failure.

Hemorrhagic fever viruses are among the agents identified by the Centers for Disease Control and Prevention (CDC) as the most likely to be used as biological weapons. Many viral hemorrhagic fevers (VHFs) can cause severe, life-threatening disease with high fatality rates.

Some viruses that cause hemorrhagic fever can spread from one person to another, once an initial person has become infected. Ebola, Marburg, Lassa and Crimean-Congo hemorrhagic fever viruses are examples. This type of secondary transmission of the virus can occur directly, through close contact with infected people or their body fluids. It can also occur indirectly, through contact with objects contaminated with infected body fluids. For example, contaminated syringes and needles have played an important role in spreading infection in outbreaks of Ebola hemorrhagic fever and Lassa fever.

For more information on Ebola, see OSHA's Ebola Webpage.

11. Which of the following are among the agents identified as the most likely to be used as biological weapons?

a. Hemorrhagic fever viruses
b. Legionella bacteria
c. Bloodborne pathogens
d. Foodborne diseases

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SDSs for chemical products have been available to workers for many years in the U.S. and other countries.

Safety Data Sheets (SDSs) on Infectious Agents

Although SDSs for chemical products have been available to workers for many years in the U.S. and other countries, Canada is the only country that has developed SDSs for infectious agents. These SDSs were produced by the Canadian Public Health Agency for personnel working in the life sciences as quick safety reference material relating to infectious microorganisms. However, NIH has developed a Pathogen Safety Data (PSD) Guide that gives information on infectious agents.

These SDSs on Infectious Agents are organized to contain health hazard information such as infectious dose, viability (including decontamination), medical information, laboratory hazard, recommended precautions, handling information and spill procedures.

For more information on these SDSs see the Canadian Public Health Agency’s Pathogen Safety Data Sheets and Risk Assessment web page.

12. Which of the following contain health hazard information such as infectious dose, viability, and recommended precautions?

a. OSHA standards covering exposure to infectious agents
b. NIOSH dose and toxicological standards
c. ANSI laboratory standards
d. Safety Data Sheets (SDSs) on Infectious Agents

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