[Biology Class Notes] on Modes of Transmission of Diseases Pdf for Exam

The spreading of any pathogen from one body to another body is termed transmission. Moreover, the transmission of infections and diseases take place in various ways, like it may get transmitted directly or through means of specific bacteria, protozoa, fungi or virus. However, primarily two modes of disease transmission are there; direct transmission and indirect transmission.

Direct Transmission

When the pathogens are directly transmitted from a person suffering from an infection, it is called direct transmission. For instance, if an open wound somehow contaminates the blood of a person who has Hepatitis B, the person with the injury may get infected with the disease too.

In this scenario, transmission occurs when an infection-free person gets in touch or exchanges bodily fluids with an individual with an infection. For instance, a pregnant woman can transfer the infection to her unborn baby through her placenta. Moreover, gonorrhoea is a sexually transferred disease that is an example of direct transmission.

During sneezing, coughing, or speaking, droplets can come out from the mouth and nose and infect a healthy person. Also, infections can spread if an infected person touches another person with his/her hands which are contaminated with the droplets. Furthermore, these droplets move a small distance as they are very minute. Hence, nearby people are prone to infections.

Here, when the skin of a person suffering from any disease touches another individual, it may infect him/her. For example, conjunctivitis, chickenpox, ringworm and head lice are some infections transmitted by skin.

As per the phrase, it is understandable that this transmission occurs when blood or body fluids make contact with the bloodstream or mucous membrane of a healthy person. The examples of such modes of transmission are cytomegalovirus, hepatitis, HIV, etc. These infections transfer via urine, semen, saliva, vaginal fluids, breastmilk, etc.

Indirect Transmission

Reversely, when pathogens are not directly transmitted from an individual suffering from an infection, it is called indirect transmission. Here, methods of disease transmission are vectors like flies, ticks, mosquitoes, dogs, etc.

Sometimes, few infections stay in the air for a considerable amount of time. As a result, it may affect a person’s immune system who comes in contact with those infections. For instance, if a healthy man/woman goes into a room where a person suffering from measles used to stay, that uninfected man/woman may catch measles.

Various objects and usable items can carry pathogens. Touching those infected items which were previously utilised by an infected individual may cause infection in a healthy human being. Its common sources are contaminated medical issues and blood transfer infections.

Various insects and flies can transmit infections. These flies and insects sit and feed on multiple animals, humans, birds and bring along disease-causing agents. Further, when they go and sit on some uninfected person, the infection may get transferred. Lyme and malaria are two examples of vector-borne diseases.

Foods that are not appropriately canned or undercooked are one of the primary sources of disease-causing infections. Moreover, drinking water is also a mode of transmission of infection. Hence, individuals must boil or filter water before drinking and using it for cooking. Bacteria named E.coli get transmitted via contaminated food items that create stomach issues.

Infection through animals takes place when a diseased animal scratches or bites an individual. Examples of diseases caused by animals are anthrax, plague and rabies.

Several infectious modes of disease transmission are available in water, plants and soil. They may come in contact with people who can cause diseases. For example, hookworm and legionnaires’ disease.

Do it Yourself

1. Which disease is caused by transmission via dog?

(a) Cholera (b) Rabies (c) Anthrax (d) Malaria