Human Health and Diseases

BiologyHuman biology


Human health is a condition of the human body that enables it to perform the tasks necessary for survival. The WHO defines health as "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity."

A disease is a state of health in which an organism cannot perform its normal functions. The causes of diseases are many and include biological factors, genetic predisposition, environmental factors, lifestyle, behavioral factors, and external agents such as pathogens (including viruses and bacteria) or parasites. Diseases may also be caused by ingrown hair or ingrown nail on your foot.

What Is Health?

The term health has come to mean something different to everyone. For some, it means being physically fit; for others, it means mental calmness; and for some, it might even be something as simple as not feeling sick. It's hard to define what the word "health" means since it has many different meanings. The same can be said about the concept of wellness. We could say that wellness is defined by the state of health or physical condition of a person or group, but that doesn't really tell us much either.

The term "wellness" is very broad and can mean many things to different people. For some, it means being physically fit; for others, it means a mental calmness; for some, it might even be something as simple as not feeling sick.

What are Diseases?

A disease is a condition where the body is no longer able to function in a normal manner. This can happen when cells malfunction or stop directly communicating with each other and working together as one. Diseases have been around since the beginning of time, affecting nearly all species of animals across the globe. Some diseases are contagious while others are not. For example, the common cold is not contagious because it is caused by viruses that live within our noses and throats. On the other hand, the flu is highly contagious because it is caused by viruses that live outside our bodies and enter our mouths.

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  • Diseases are not always easy to detect, and that’s where doctors come in. Doctors can give patients tests or exams to determine the cause of the disease and what type of treatment will work best

  • Diseases are caused by something (or several somethings) that we call pathogens. Pathogens are microorganisms, mainly bacteria, and viruses, which are either parasitic or commensal. Parasitic means that the microorganisms live on or in another organism for food or nutrients; commensal refers to a relationship between two organisms where one benefits from the other, but neither is harmed.

  • The various pathogens we have on Earth constantly evolve and change via mutation. Bacteria are especially good at this because they reproduce quickly. For example, bacteria can adapt to antibiotics, so doctors always make sure to prescribe the correct dosage for an infection.

    Bacteria that cause diseases can be either infectious or non-infectious. Infectious diseases are caused by infectious pathogens, like the bacteria that cause cholera, whooping cough, and tuberculosis. Non-infectious diseases are caused by non-infectious pathogens, like chemicals (like asbestos), physical agents (like radiation), or a combination of things (like atherosclerosis).

Some Common Diseases In Humans

  • Hepatitis is a viral infection of the liver. Symptoms include feeling very tired, yellow eyes and skin, loss of appetite, nausea, abdominal pain, and some fever. The disease is spread through contact with infected blood or body fluids. There's no cure for this disease, but antiviral medications can treat it.

  • Tetanus is rare in non-travelers, but travelers should be vaccinated against this disease. Symptoms include muscle spasms and painful convulsions. It's caused by bacteria getting into an open wound. Tetanus can be treated with antibiotics to prevent it from spreading throughout the body and causing life-threatening complications such as brain and heart infections.

  • Malaria is caused by a parasite that's transmitted to humans through mosquito bites. The symptoms include high fever, shaking, chills, headache, vomiting, and sweating during the first few days after infection, which may last for several weeks afterward. Malaria is fatal if not treated properly. It's mostly found in Africa and South America.

  • Typhoid fever is caused by the bacteria Salmonella typhi, which usually spreads from person to person through contaminated food or water. The symptoms include headache, weakness, loss of appetite, and abdominal pain that may last for several weeks. Typhoid can be treated with antibiotics to prevent it from spreading throughout the body and causing life-threatening complications such as brain and heart infections

    Ebola is a rare and deadly disease that causes fever, severe headache, muscle pain, weakness, fatigue, and sore throat. It also causes bleeding inside and outside the body.


Your immune system is your body's first and last defense against disease. It protects you from the flu, Ebola, and the common cold−you name it, your immune system fights it.

The immune system is pretty complex, but here's a very basic description− when foreign substances (like bacteria or viruses) enter the body, antibodies help the body recognize and attack them. The whole process is actually really cool−the immune system has memory, so if a certain bacteria or virus tries to attack again at some point in the future, your body will recognize it and be able to fight it off much more quickly than if it was an entirely new thing.

When you get sick with something like the flu, it's because your immune system isn't working properly.

Active and Passive Immunity

When you get a cold, your nasal membranes and throat secrete mucus to trap bacteria and viruses so the immune system can neutralize them. During this process, white blood cells release chemicals into the bloodstream to fight the infection. If you've had chickenpox or measles, your body is familiar with the antigens of those viruses, so it is ready for them when you get them again.

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Passive immunity is when antibodies are transferred from one individual (the "immune donor") to another (the "immune recipient"), usually through an injection or infusion. This is most common in newborn infants (who are given immunoglobulin antibodies from their mothers), but also occurs with vaccinations and transfusions. These antibodies can protect against certain bacterial infections, such as meningitis or pneumonia, but don't last very long without further boosters.

Active immunity is when your body creates its own antibodies after being exposed to a pathogen. This can come from vaccination (an inactive form of bacteria or virus that trains the immune system to recognize it) or from surviving an actual infection. The advantage of active immunity is that it protects against future infections of the same kind (and sometimes other kinds).


The AIDS pandemic, caused by the human immunodeficiency virus (HIV), is a disease that affects people of all ages, races, and sexual orientations. It spreads the most through body fluids, especially semen and blood. When HIV infects someone, it comes help from other viruses. This is called a coinfection when someone has more than one disease at once.

Treatment for AIDS includes taking antiretroviral drugs that keep the virus from getting stronger and spreading throughout the body. These drugs can also reduce the risk of getting certain infections and cancers. There is currently no cure for HIV/AIDS, but some treatments can control it so that a person can live with HIV without any problems.


In conclusion, human health and diseases are a complex topic with many different contributing factors. There is still much to be learned about how to best prevent and treat diseases, but the progress that has been made is impressive. With continued research and advances in medical technology, we can only hope that even more progress will be made in the future.


1. What are the four main types of human health and disease?

Human health is a state of optimal physical, emotional, and social wellbeing. Diseases are disorders of the body that can include symptoms such as pain, fatigue, and disturbed body systems function.

2. What is the difference between an infectious and non-infectious disease?

An infectious disease is one that is caused by microorganisms such as bacteria or viruses, whereas a non-infectious disease is caused due to injuries, toxins, and other physical factors. Infectious diseases can be transmitted from one individual to another through contact with contaminated objects or even through bites of insects etc., whereas non-infectious diseases are not transmitted from one person to another but occur naturally in every individual due to some inherent weakness in the body.

3. What are some examples of diseases?

Some examples are AIDS/HIV (Acquired Immune Deficiency Syndrome), Cancer, Diabetes Mellitus (Type 1), Klinefelter’s Syndrome (XXY), Hemophilia A & B, and Huntington's Disease (HD), etc.

4. What are the causes of diseases?

There are many causes that can lead to the development of a disease. Some common examples include genetic disorders, environmental factors (pollution, radiation, etc.), infections from microorganisms like bacteria and viruses, certain physical injuries/traumas, etc., and unhealthy lifestyles (unbalanced diet, lack of exercise, etc.)

Updated on 13-Oct-2022 11:19:47