Diseases: Definition, Types and Causes

Diseases refer to abnormalities in the body of a living organism, causing discomfort because of organs or organ systems being affected. The diagnosis of a disease can be done through the symptoms or signs that it shows in the body. This helps to cure the disease under the supervision of an expert physician. Diseases can often be classified into different categories depending on the basis such as duration and the spread of infection. All know about numerous diseases which have their characteristics, causes, and more. Thus, when we compare some to the others, we see that we can easily detect some while the others are detected in the later stage of life. Hygiene is also often considered as a primary reason for diseases too. Hence, it is important to maintain cleanliness. Let’s discuss the topic in detail along with some important questions. 

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What is Disease?

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There are many diseases deemed to be contagious or infectious, which means that they transmit from one individual to the other. This happens through various means such as air, water, humans, contaminated food, or through vectors. Microbial agents tend to transfer from the body of an infected individual to that of a non-infected one.

These microbial agents potentially cause the infection to spread through the air as tiny, invisible droplets that come out when diseased individuals cough or sneeze. This results in the ambient air harboring microbes and transmits the infection to other healthy bodies. Some common diseases spreading through the air include pneumonia, tuberculosis, common cold, and so on. These diseases are likely to spread more in case of a crowded ecosystem.

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Causes of Diseases

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Sexual Contact: These are infections that spread while having sex with an infected person. Examples of sexually transmitted diseases are – AIDS, Syphilis, Gonorrhoea. These diseases are not spread through casual contact with an infected person such as hugs, handshakes, eating in their vicinity, playing sports, or any other way in which we interact with them socially.

Virus: The virus that causes AIDS is called HIV. It spreads through sexual or blood-to-blood contact between two individuals. It can also spread from a mother to her baby during the gestation or breastfeeding period. Viruses also cause several other infections. One of the best examples is the recently spreading coronavirus that spreads the Covid-19 infection. It spread through the air from one person to another due to the nose and mouth sputum of an infected individual.

Other microbes: Another mode by which diseases spread is water. This occurs when the excreta of an infected person get mixed with potable water in a community, for example, the excreta can be from a person diagnosed with cholera. Microbes are responsible for causing cholera to enter the system of a non-infected person once the water is consumed causing cholera to spread. Proper treatment of drinking water can be helpful to keep a check on water-borne diseases.

Animals: Animals can act as hosts as they have the potential to carry pathogens and cause diseases to other animals and humans too, which usually occurs through direct contact. These animals are called vectors as they act as intermediaries carrying the infected agents. Mosquitoes are one of the most common vectors. Female mosquitoes require nutrition-rich food to produce mature eggs. They usually obtain the required nutrition by feeding on human blood, hence transmitting diseases.

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Types of Diseases

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Based on Duration

Acute diseases: These types of diseases are those, which occur for a short period. However, if not treated with the utmost care, they might turn to become chronic diseases.

Examples of such diseases include common cold, minor burns, and so on.

Chronic diseases: These ailments last for a long period and are tedious to treat.

Examples of such diseases are heart and kidney illnesses.

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Based on the Spread of Infection

Communicable: Infectious or contagious diseases are those transmitted from one organism to another. An infectious disease spreads from one person to another through a variety of ways that include contact with blood and bodily fluids, breathing an airborne virus, or an insect bite.

Non- communicable: non-communicable diseases or NCDs are generally long-lasting and progress slowly, and thus they are sometimes also referred to as chronic diseases. They can also result from exposure to adverse environments or from genetically determined abnormalities, which may be seen at birth, or which may become apparent later in life.

Communicable Diseases

1. Examples – Flu, Mumps, Measles, TB, HIV/AIDS, Hepatitis A, B, and C.
2. Causes – Animal parasites, bacteria, fungi, viruses, and contact with an infected person.
3. Symptoms – Fever, weakness, muscle, and body ache, diarrhea, congestion, and coughing.
4. Treatment - Antibiotics for bacterial infections, viral infection with antiviral medication, rest and therapies, fungal and parasitic infections are treated with antifungal and antiphrastic medications.
5. Asymptomatic Transmission: Sometimes we hear a lot about the asymptomatic condition, particularly concerning the spread of COVID19. Asymptomatic transmission refers to a transmission of the virus from a person who does not develop or show any symptoms. People who are infected with COVID19 could likely transmit the virus before they develop any signs or symptoms. It is vital to know that pre-symptomatic transmission requires the virus to spread through infected droplets or through touching contaminated surfaces.

Nearly fifty percent of infections of regular seasonal flu may be asymptomatic. It may be in part due to pre-existing partial immunity. It may also be the case when asymptomatic patients shed their virus presence and can transmit the disease but not at the same rate as symptomatic persons. Now, it becomes a case of an invisible transmission of the virus.

It is important to note that 75 percent of people who have flu show no symptoms for a long time. It is tough to call this situation good or bad. It can be good that many people with flu do not experience symptoms and hardship. However, to limit the spread of a pandemic, this can be a stressful situation as it would be unclear who is infected and who is not.

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Non-Communicable Diseases

Examples of Major Non–Communicable Diseases Include:

1 - Cancer

2 - Cardiovascular disease (Heart Attack, Stroke),

3 - Chronic Respiratory Disease (Asthma), and

4 - Diabetes Mellitus.

Causes – Social determinants to health, tobacco, alcohol, poor nutrition, physical inactivity, family history, age, and gender.

Symptoms – the signs and symptoms of NCD differ in each case. Diabetes is a condition that can affect many other systems in the body. The symptoms of diabetes include- feeling very thirsty, frequent urination, feeling very hungry or tired, weight loss, sores that heal slowly, dry, and itchy skin, tingling in the feet, and blurry eyesight.

Treatment – There is no permanent cure for NCDs. Medications and therapies help in relieving most of the symptoms. NCDs are lifestyle diseases. Prevention and management are better than cure in the case of NCDs. In the case of cancer, early diagnosis helps in treatment. Lifestyle changes such as giving up on smoking and alcohol can bring about improvements in the case of NCDs.

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Points to Remember

• Diseases refer to abnormalities in the body of a living organism, causing discomfort because of organs or organ systems being affected.
• There are many diseases deemed to be contagious or infectious, which means that they transmit from one individual to the other. This happens through various means such as air, water, humans, contaminated food, or through vectors. These microbial agents potentially cause the infection to spread through the air as tiny, invisible droplets that come out when diseased individuals cough or sneeze. 
• This results in the ambient air harboring microbes and transmits the infection to other healthy bodies. Some common diseases spreading through the air include pneumonia, tuberculosis, common cold, and so on.
• Infectious or contagious diseases are those transmitted from one organism to another. An infectious disease spreads from one person to another through a variety of ways that include contact with blood and bodily fluids, breathing an airborne virus, or an insect bite.
• Non-communicable diseases or NCDs are generally long-lasting and progress slowly, and thus they are sometimes also referred to as chronic diseases. 
• They can also result from exposure to adverse environments or from genetically determined abnormalities, which may be seen at birth, or which may become apparent later in life.
• Nearly fifty percent of infections of regular seasonal flu may be asymptomatic. It may be in part due to pre-existing partial immunity. It may also be the case when asymptomatic patients shed their virus presence and can transmit the disease but not at the same rate.

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