Infectious diseases, caused by certain type of viruses, bacteria, parasites and fungi, are transmitted form person to person by direct or indirect contact.
Mechanisms of Transmission of Microorganisms:
Direct Contact Transmission
Indirect Contact Transmission
Droplet Contact Transmission
Airborne Transmission
Animal Transmission
Fecal-Oral Transmission
Animal to Person Transmission
Direct contact transmission is the physical transfer of microorganisms from an infected person to an uninfected person. It occurs by touching, kissing, sexual contact, contact with open lesions or bodily secretions, or by transmission through the placenta to an unborn child. This type of microorganism does not survive for long periods of time away from the host. E.g. gonorrhea can be transmitted from mother to child during childbirth.
An infected person can cause a surface to become contaminated through contact. On the host surface, the microorganism can survive for an extended period of time and then be transferred to an uninfected person by indirect contact. E.g. Norovirus
Microorganisms can also be transferred indirectly by infected droplets contacting surfaces of the eye, nose or mouth or with an open lesion. Sneezing, coughing and talking when infected with a disease can create droplets containing microorganisms, which are too large to be airborne for long periods of time and will settle out of the air and onto surfaces. E.g. SARS, measles
Airborne transmission are situations where the infected droplet nuclei or dust particles containing the microorganisms remain suspended in air for a long period of time. These organisms enter the upper and lower respiratory tracts of susceptible persons. E.g. TB, chickenpox, measles
Vectors, such as mosquitos, flies, mites, fleas, ticks, rodents and dogs, which can transmit disease. Since vectors are mobile, they increase the transmission range of the disease. Transmission of the disease can occur through biting or from the feces of a vector. E.g. West Nile virus
Fecal-Oral Transmission occurs when microorganisms enter the body through ingestion of food and water infecting the digestive system. These organisms multiple in the body and are expelled in the feces, which then can contaminate the water supply and food sources.
Animal diseases can be transmitted through animal bites or scratches or the handling of animal waste. It is thought that the coronavirus outbreak was caused by an animal to human transmission.
Prevention of Disease Transmission
You can prevent direct and indirect transmission of disease by washing your hands or using a sanitizer. Indirect transmission occurs by coughing or sneezing causing microorganisms to land on a hard surface, where the organism can live for a period of time until it is transferred by touch to one’s face.
1. Handwashing – Use soap or antibacterial soap and was with warm water, rubbing your hands together for at least 20 seconds.
2. Alcohol based sanitizers – Rub 2 ml of an alcohol-based sanitizer over all surfaces of the hands. Standard alcohol based hand sanitizers will kill most germs except for non-enveloped viruses (E.g. the common cold, “pink eye,” poliovirus, norovirus) within 15 seconds and have no persistence. In other words, you can become infected again as soon as you touch another infected surface.
3. QUAT based sanitizers (benzethonium chloride and benzalkonium chloride) and CHG (chlorohexidine gluconate) – Rub the amount directed on the labeling of a QUAT or CHG sanitizer over all surfaces of the hands. Some QUATS provide immediate kill (15 sec) while CHG can take 30 60 seconds. All of these products are persistent for several hours. E.g. Biocleanse, Zylast, SafeHands, Hibiclens. It is important to read the science behind each sanitizer as some can still kill germs at 99.9% for six hours while others advertise 24 hours, but may only be 10% effective at that time. Select one with 99% plus protection for several hours. We highly recommend these sanitizers as you cannot wash your hands or use alcohol based sanitizers enough to provide the same protection as achieved with these sanitizers.
4. Masks – simple surgical masks can prevent the airborne transmission of microorganisms to the nose and mouth. However, masks can create additional difficulties if people rub their face more frequently, turn an exposed mask inside-out, or transfer germs from the mask to their hands.
5. N95 masks – these masks are designed to prevent infectious particles of <5 microns from being transmitted to the nose and mouth. Examples of aerosols that meet this criteria are influenzae and coronavirus. These masks are made to fit closely to the nose and skin. In the Retrospective Protection Effectiveness Clinical Trial, these two masks were compared in 2862 healthcare workers. While N95 showed better effectiveness, the statistical analysis is not yet complete and scientists are concerned that the difficulty of breathing through these masks may cause people to remove them more frequently decreasing the effectiveness of the mask.
6. Protective Eyewear – Shields or large glasses can protect against microorganisms from conjunctiva of the eye.
7. Personal Protective Equipment – recommended for healthcare workers at high risk of exposure to indirect or airborne exposure of microorganisms. Extensive training is required to don and remove this equipment without increasing exposure.
8. Vaccinations – can drastically reduce your risk of becoming ill with an infectious disease. Despite this fact, only half of Americans take a flu shot. Vaccinations are frequently not available for a newly discovered disease and can take 1-2 years to develop, e.g. coronavirus.
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