infection agents

What are Infectious agents?

Best Blog November 25, 2022

Infectious agents are organisms that are capable of producing infection or infectious disease. They include bacteriafungiviruses, and parasites. Healthcare workers have a high risk of contact with infectious agents due to the various types of activities involved with their jobs and the possibilities of contamination.

Bloodborne Infectious Diseases: HIV/AIDS, Hepatitis B, Hepatitis C: Exposures to blood and other body fluids occur across a wide variety of occupations. Healthcare workers, emergency response and public safety personnel, and other workers can be exposed to blood through needle sticks and other sharps injuries, mucous membranes, and skin exposures. The pathogens of primary concern are the human immunodeficiency virus (HIV), hepatitis B virus (HBV), and hepatitis C virus (HCV). Workers and employers should take advantage of available engineering controls and work practices to prevent exposure to blood and other body fluids.

Influenza (Flu) and Coronavirus Disease 2019 (COVID-19):

  • Getting vaccinated is especially important this year because some of the same symptoms can occur in people with either flu or COVID-19, so people with those symptoms might have to be evaluated for both types of infection.
  • Vaccination for influenza will not protect against COVID-19.  When a vaccine for COVID-19 becomes available, follow your healthcare provider’s recommendations for COVID-19 vaccination.

Ebola Virus Disease:

Ebola is a severe and often fatal disease in humans. It is also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever. The 2014 Ebola outbreak is the largest Ebola outbreak in history and the first in West Africa. The U.S. Centers for Disease Control and Prevention (CDC) and partners are taking precautions to prevent the spread of Ebola within the United States.

CDC has developed Ebola prevention and control recommendations for healthcare workers, laboratory workers, air medical transport, mortuary and funeral workers, and first responders such as firefighters, emergency medical technicians, and police officers. CDC has also developed guidance for airline workers, wastewater workers, and humanitarian workers.



Transmission of tuberculosis (TB) is a risk in healthcare and other congregate settings where many people share the same space for extended periods of time. Prisons, jails, homeless and social assistance shelters, and emergency shelters are examples of congregate spaces where the spread of TB often occurs. Transmission of disease in these spaces is most likely to occur when patients, prisoners, or shelter clients have unrecognized TB or have received ineffective or incomplete treatment for the known diseases.

TB is a contagious and potentially life-threatening infectious disease caused by a bacterium called Mycobacterium tuberculosis. The TB bacteria are spread from person to person through the air. People with TB disease of the lungs or larynx release the bacteria into the surrounding area when they cough, sneeze, talk, or otherwise expel air, dispersing droplets that contain M. tuberculosis. These droplets can dry into tiny particles called droplet nuclei that remain suspended in the air for long periods of time. Other people can breathe the infectious particles into their lungs and become infected. Infection usually requires prolonged sharing of airspace with a person actively spreading TB bacteria into the area. In rare cases, TB infection has been documented after short exposures to such persons with active TB. After becoming infected, most people’s immune systems are able to contain the infection but are not able to eliminate it without help from anti-TB drugs. These people have latent TB infection and remain infected until corrective treatment is completed. Latent TB infection does not cause symptoms and is not contagious. However, without treatment, infected people can lose control of the infection and develop active clinical disease. People with active TB have symptoms and can spread the disease. The risk of developing active TB disease is greatest in the first few years after infection, but some risk remains throughout life.

TB is preventable and, in most cases, treatable. Infection control practices can help reduce the risk of TB transmission. Treatment of persons with latent TB infection can prevent the subsequent development of active TB, and TB disease can usually be cured by available anti-TB drugs. Even persons with drug-resistant strains can often be cured by alternative regimens of medications.

Severe Acute Respiratory Syndrome:

Severe acute respiratory syndrome (SARS) is a viral respiratory illness. It was first identified in China in late 2002 and was reported in Asia in February 2003. Over the next few months, SARS spread to more than two dozen countries in North America, South America, Europe, and Asia before it was contained. Although there have been very few cases of occupationally acquired SARS in the United States, NIOSH recognizes the potential for the spread of the disease within the workplace, especially for workers who experience daily contact with the general public, such as health care, medical transport, and airline personnel, as well as those who deal directly with potentially SARS infected material, such as laboratorians. The following topic page is designed to present general information about the disease, increase awareness of safety precautions and work-related issues, and provide links to additional information for workers and employers.

Hepatitis B:


Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus (HBV). It is a major global health problem. It can cause chronic infection and puts people at high risk of death from cirrhosis and liver cancer.

A safe and effective vaccine that offers 98% to 100% protection against hepatitis B is available. Preventing hepatitis B infection averts the development of complications including chronic disease and liver cancer.

The burden of hepatitis B infection is highest in the WHO Western Pacific Region and the WHO African Region, where 116 million and 81 million people, respectively, are chronically infected. Sixty million people are infected in the WHO Eastern Mediterranean Region, 18 million in the WHO South-East Asia Region, 14 million in the WHO European Region, and 5 million in the WHO Region of the Americas.


In highly endemic areas, hepatitis B is most commonly spread from mother to child at birth (perinatal transmission) or through horizontal transmission (exposure to infected blood), especially from an infected child to an uninfected child during the first 5 years of life. The development of chronic infection is common in infants infected by their mothers or before the age of 5 years.

Hepatitis B is also spread by needlestick injury, tattooing, piercing, and exposure to infected blood and body fluids, such as saliva and menstrual, vaginal, and seminal fluids. Transmission of the virus may also occur through the reuse of contaminated needles and syringes or sharp objects either in health care settings, in the community, or among persons who inject drugs. Sexual transmission is more prevalent in unvaccinated persons with multiple sexual partners.

Hepatitis B infection acquired in adulthood leads to chronic hepatitis in less than 5% of cases, whereas infection in infancy and early childhood leads to chronic hepatitis in about 95% of cases. This is the basis for strengthening and prioritizing infant and childhood vaccination.

The hepatitis B virus can survive outside the body for at least 7 days. During this time, the virus can still cause infection if it enters the body of a person who is not protected by the vaccine. The incubation period of the hepatitis B virus ranges from 30 to 180 days. The virus may be detected within 30 to 60 days after infection and can persist and develop into chronic hepatitis B, especially when transmitted in infancy or childhood.


Most people do not experience any symptoms when newly infected. However, some people have acute illness with symptoms that last several weeks, including yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting, and abdominal pain. People with acute hepatitis can develop acute liver failure, which can lead to death. Among the long-term complications of HBV infections, a  subset of persons develops advanced liver diseases such as cirrhosis and hepatocellular carcinoma, which cause high morbidity and mortality.

HBV-HIV confection

About 1% of persons living with HBV infection (2.7 million people) are also infected with HIV. Conversely, the global prevalence of HBV infection in HIV-infected persons is 7.4%. Since 2015, WHO has recommended treatment for everyone diagnosed with HIV infection, regardless of the stage of the disease. Tenofovir, which is included in the treatment combinations recommended as first-line therapy for HIV infection, is also active against HBV.