Disease: – A disease is a physiological condition in which the human body fights against the external or internal causes of infection. On the basis of externally caused diseases, various examples are present, ranging from bacteria, viruses, protozoans, helminths, and many more.
Pathogen: – The pathogen is an organism that causes a disease in another organism (Host) to complete its life cycle or survival. The pathogens have a wide range of adaptability towards the host’s body environment, which helps them to enter through different routes (mouth, blood, nose, and various other modes.)
Diseases Caused by Bacteria
Following are some diseases caused by the bacteria:
Typhoid
- Caused by a bacterium called Salmonella typhi
- It generally enters the body through contaminated food and water and migrates to other organs through blood.
- Symptoms: High fever, weakness, stomach pain, constipation, headache, and loss of appetite. Furthermore, Intestinal perforation and death can also be reported in some cases.
- Diagnostic Test: – Widal Test
(Note: – Famous example: – Mary Mallon, also known as Typhoid Marry, was a cook and a carrier of typhoid. She spread typhoid for many years, unknowingly that she is suffering from typhoid).
For more information also read: Typhoid
Pneumonia
- Caused by two bacteria called Streptococcus pneumoniae and Haemophilus influenzae.
- The infection acquires by inhaling the droplets and aerosols released by an infected person or even by sharing glasses and utensils with an infected person.
- The infected organ in the human body: alveoli (air-filled sacs) of the lungs. (Note: – The alveoli get filled with fluid leading to several respiration problems.
- Symptoms: Fever, chills, cough, and headache. (Note: – In some severe cases, it has been seen that the lips and fingernails turn grey to bluish in color)
Disease Caused by Viruses
Following are the disease caused by viruses:
Common Cold
- Caused by Rhinoviruses (It is a group of most infectious human ailment viruses).
- The infection acquires by inhaling Droplets from the cough/sneezing of an infected person or through contaminated objects, e.g. computer keyboard or mouse, pen, etc.
- The infected organ in the human body: -nose and respiratory passage but not the lungs
- Symptoms: Nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc., usually lasting for 3-7 days.
Also read: Human Respiratory System
Disease Caused by Protozoan
Following are the disease caused by protozoan:
Malaria
- Caused by Plasmodium (P. vivax, P. malaria, and P. falciparum)
- Furthermore, malaria caused by P. falciparum is the most serious and can even be fatal also.
- The primary host of Plasmodium is the female Anopheles mosquito, whereas the secondary host is Humans.
Life Cycle of Plasmodium
Inside the Human Body
- The Plasmodium enters the human body as sporozoites (an infectious form of Plasmodium) when an infected female Anopheles bites the human.
- The sporozoites initially multiply inside the liver and increase them (by reproducing asexually).
- After increasing their number, the parasite releases into the blood and attacks RBCs (Red blood Corpuscles)
- In RBC, the parasite increases its number and produces male as well as female gametes, which results in a burst of RBC.
- The rupture of RBC results in releasing a toxic substance called hemozoin.
- Hemozoin is a substance that shows the symptoms: – of high chill fever, recurring every three to four days.
Inside the female Anopheles Mosquito:
- The parasite enters inside the mosquito when it bites an infected person.
- These parasites enter the mosquito’s body, and the male and female gametes fuse there and ultimately produce a zygote and undergo further development.
- The parasites multiply there to form sporozoites that are stored in their salivary glands.
- When these mosquitoes bite a person again, the cycle again continues.
Amoebiasis
- Caused by Entamoeba histolytica, a parasite of the large intestine of humans.
- Symptoms: Constipation, abdominal pain, cramps, stools with excess mucous, and blood clots.
- Vector: Houseflies (acts as carriers and spreads to transmit the parasite from the feces of an infected person to food and food products.).
- Sources of infection: Drinking water and food contaminated by fecal matter.
Diseases Caused by Nematodes
The following are the disease caused by Nematodes:
Elephantiasis or Filariasis
- Caused by Wuchereria (W. bancrofti and W. malayi), commonly known as filarial worms
- Vector: Female mosquito vectors (Infection transmitted to the healthy person through the bite of female mosquito vectors).
- The chronic inflammation of the organs develops due to the long-term residence of filarial worms there.
Ascariasis
- Caused by Ascaris, commonly known as roundworms (intestinal parasites).
- Symptoms: Internal bleeding, muscular pain, fever, anemia, and blockage of the intestinal passage.
- The eggs of the parasite are excreted along with the feces which ultimately contaminate water, plants, etc.
- A healthy person acquires the infection by consuming contaminated water, vegetables, fruits, etc.
Diseases caused by Fungi
Following are the disease caused by fungi:
Ringworm Infection
- Caused by fungi belonging to the genera Microsporum, Trichophyton, and Epidermophyton.
- Symptoms: Appearance of dry, scaly lesions (accompanied by intense itching) on various parts of the body such as skin, nails, and scalp.
- Infection is acquired by: Using towels, clothes, or even the comb of infected individuals. Heat and moisture help these fungi to grow, and most commonly infections thrive in skin folds such as those in the groin or between the toes.
FAQs on Common Diseases in Humans
Question 1: Name the infectious agents along with the symptoms of the Common Cold.
Answer:
The infectious agent and Symptoms of the common cold are:
- Infectious Agent: Rhinoviruses
- Symptoms: Nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc., usually lasting for 3-7 days.
Question 2: What are the 4 Major Diseases?
Answer:
Following are the four major diseases; Typhoid (Caused by Salmonella typhi), Pneumonia (Caused by Streptococcus pneumoniae and Haemophilus influenza), Common Cold (Caused by Rhinoviruses), Malaria (Caused by P. vivax, P. malaria and P. falciparum).
Question 3: What is the most Common Disease in Humans?
Answer:
The most common disease in humans is the Common Cold caused by Rhinoviruses.