Infectious and Non-Infectious
Disease
by Stevie-Jade Vickers
What is disease?
By definition, a disease is a disorder of structure or function in a human, animal,
or plant, especially one that produces specific symptoms or that affects a specific
location and is not a direct result of physical injury. Diseases can be
communicable or non-communicable. A communicable disease is a disease which
can be spread from one person, animal, or plant to another (also known as a
contagious disease or infectious disease). A non-communicable disease is a
disease which cannot be spread, otherwise known as non-infectious or not
contagious. Examples of communicable diseases are HIV or measles. Cancer is an
example of a non-communicable disease as it cannot be spread.
Infectious Diseases (Communicable Diseases)
Infectious diseases are diseases which can be transmitted by direct contact, through the air or by water. Infectious diseases are
caused by pathogens. Pathogens are microorganisms. Pathogens are dependent on their host for the supply of conditions and
nutrients required for them to grow and thrive and reproduce. There are five types of pathogens: viruses, bacteria, protists,
fungi, and parasites.
Infectious diseases do not cause symptoms to develop immediately after infecting a person. The pathogen enters an organism
(an animal, human or plant) and then begins to reproduce rapidly in conditions ideal for increasing numbers of the pathogen.
This is known as the incubation period. Harmful toxins are then made by the pathogen. Symptoms such as fevers and headaches
begin to develop.
Bacteria
Bacteria are single-celled, prokaryotic microorganisms. Bacteria have
three basic shapes. There are round bacteria which are named cocci. A
single, round bacteria is called a coccus. Examples of spherical bacteria
are Staphylococcus (this can cause staph infections such as boils) and
Streptococcus (this can cause strep throat and pneumonia). Cylindrical
shaped bacteria are called bacilli and a single, cylindrical bacteria is called Cocci
a bacillus. An example of a bacillus is Escherichia coli (also known as E
Coli) which can cause cholecystitis, urinary tract infections, cholangitis
and also pneumonia and meningitis. Spiral shaped bacteria are called
spirilla and a single, spiral shaped bacteria is known as a spirillum. An
,example or spirilla is helicobacter pylori which affects the stomach by damaging the tissue of the stomach, leading to pain and
inflammation. These bacteria are also responsible for causing peptic ulcers located in the upper digestive tract.
Not all bacteria are harmful pathogens. In fact, many bacteria are useful.
Bacteria can be used to make cheese and yoghurt, to formulate
medicines and to break down our waste.
Bacteria is spread by ingesting contaminated food and water and via
direct contact.
Tuberculosis Spirilla
What is Tuberculosis and what are the causes
and who is at risk?
Tuberculosis is a bacterial disease caused by the bacteria known as Mycobacterium tuberculosis. This bacterium commonly
affects the lungs. Tuberculosis which affects the
lungs is known as pulmonary tuberculosis and is
the most infectious form of tuberculosis. However,
it can also impact the abdomen, the bones, the
glands, and the nervous system. Mycobacterium
tuberculosis is a bacillus.
Tuberculosis is transmitted between people via the
air. Coughing and sneezing releases particles
containing the bacteria into the air. People most at Mycobacterium
risk of infection of this bacterial disease live in Tuberculosis in the lungs
developing countries. Countries such as the United
States of America and the United Kingdom rarely face tuberculosis cases. South-East Asia had the largest number of tuberculosis
cases in 2019. People can contract the disease at any age; however,
adults are mostly affected. Furthermore, people who have HIV are
eighteen times more likely to develop the disease, as well as people
who already have conditions which reduce the impact of their immune
system.
How is it diagnosed?
To test for tuberculosis, the World Health Organisation suggests using
rapid molecular diagnostic tests for initial diagnostics. The reasoning for
this is that the accuracy of these tests is extremely high and can help
with early diagnosis of tuberculosis as well as drug-resistant X-ray showing tuberculosis
tuberculosis.
Multidrug-resistant tuberculosis is a type of the disease where the
bacteria do not respond to the anti-tuberculosis medications rifampicin and isoniazid. It is more complex and expensive to
diagnose than regular tuberculosis.
What are the symptoms and how does Tuberculosis progress over time?
People who have contracted tuberculosis may not receive treatment for a prolonged period as their symptoms may seem too
mild for concern and they may not even know they have the disease. This can lead to death in around 45% of HIV-negative
people and nearly all HIV-positive people.
The body’s immune system detects the presence of foreign materials such as bacteria and viruses and usually defends the body
against them and kills them, resulting in few to no symptoms. However, the immune system, especially when it has never been
exposed to the foreign material before, cannot always kill the bacteria but can stop the bacteria from spreading throughout the
body. This also results in no symptoms. However, the bacteria will still be present in the body which is known as latent
tuberculosis. People who have latent tuberculosis cannot spread tuberculosis to other people. If the immune system fails to
,contain the infection, the bacteria can spread throughout the body causing symptoms to develop which is called active
tuberculosis.
The most common symptoms of tuberculosis include a persistent, phlegmy cough, unexplained weight loss, fatigue, sudden loss
of appetite, high temperatures and night sweats and swelling in the neck.
What are the treatments?
Tuberculosis is both preventable and curable. The form of tuberculosis which responds to drugs is treated using a six-month
course of antibiotics. Various antibiotics can be prescribed for the treatment of tuberculosis and this is since there are strains of
mycobacterium tuberculosis which are resistant to some types of antibiotics.
Viruses
Viruses are not living cells unlike bacteria. They contain a
single strand of genetic material inside a layer called a
protein coat which replicates inside the cells of its host
(human, animal, or plant) to make new viruses which are
then released. Viruses can be spread via droplet infection
which involves talking, coughing, and sneezing. They can also
be spread by direct contact such as the exchange of body
fluids or entry through open wound sites.
Treating viral infections is more difficult than treating
bacterial infections. Bacteria survive outside body cells
Viruses
whereas viruses require a host cell to thrive. They reside
inside body cells. Bacterial infections are usually treated with
prescribed antibiotics however, viruses are protected from drugs inside host cells. Vaccinations are usually given for some types
of viruses to protect us against contracting these diseases which can sometimes be fatal.
Common examples of viral diseases are measles, rubella, and COVID-19 (coronavirus). Polio disease is also caused by a virus.
Polio
What is Polio, how is it caused and who is at risk?
Poliomyelitis (also known as polio) is a highly infectious viral disease caused by the
virus poliovirus which invades the nervous system. This viral disease infects
predominantly young children under the age of five years old. Polio disease can be
life threatening as between 5%-10% of people paralysed by the disease die due to
the immobilisation of their breathing muscles.
Poliovirus is spread via the faecal-oral route which means faeces which is
contaminated by one person is somehow ingested by another person, causing them
to become infected. Droplets from coughs or sneezes may also spread the virus.
Another method of transmittance is via contaminated food and water being
ingested. The virus enters the buccal cavity and travels to the throat and to the Poliovirus
bowels. It is here that the virus begins to multiply. In some cases, the virus can make
its way into the bloodstream and spread to the nervous system, potentially
causing paralysis.
Vaccination programmes have resulted in poliovirus being wiped out in
most, but not all, parts of the world. Europe, southeast Asia, the western
Pacific region, and the Americas have officially been declared ‘polio-free’
Poliovirus
, by WHO (The World Health Organisation). However, places such as Nigeria, Afghanistan and Pakistan are still at significant risk of
infection of poliovirus.
What are the symptoms?
Symptoms of polio disease can start off as a fever with a high temperature of 38 degrees or above, headache, stiffness of the
neck, a sore throat, pain in the limbs and abdomen, fatigue and vomiting. These symptoms often pass within a week. However,
many people with the disease do not experience any symptoms. Typically, people without symptoms have a stronger immune
system and will often be able to fight the infection without acknowledging its presence to begin with.
More serious symptoms which affect the spinal cord, and the brain are developed by a smaller amount of people with polio
disease. These symptoms include paraesthesia which is the feeling of pins and needles in the legs. Meningitis is also a more
severe symptom which affects around 1 in 25 of people suffering with polio disease and is the infection of the covering of the
spinal cord and/or brain. Lastly, paralysis affects around 1 in 200 people who have polio disease. However, this paralysis tends to
be temporary, and movement should begin to return within a matter of weeks or months.
How does Polio progress?
1 in 200 cases of polio results in irreversible paralysis (often in the legs). This occurs
when the poliovirus begins to attack the nerves located in the spine and at the base of
the brain. The paralysis develops over hours or days and is not usually permanent.
Movement generally begins to return over a period of weeks and months. However, in
some cases, people can be left with permanent defects such as weakened breathing
muscles which can become severe and can lead to death eventually as the breathing
muscles can become immobilised. Muscle weakness can become a lifelong problem for
people with or who have had poliovirus and may require long-term treatment. Atrophy
(a condition in which the muscles begin to shrink) can also become a permanent, lifelong
problem. Contractures (tight joints) and deformities like twisted legs or feet may also
become quite prevalent and require long-term treatment and support plans.
Another disorder of progressed polio disease is called post-polio syndrome and is a
condition where the patient who has had polio previously begins to suffer similar
symptoms or where their existing symptoms become worse. Post-polio syndrome
Polio Disease Deformity typically affects 25-40 in every 100 polio survivors. Post-polio syndrome can occur
anywhere from 10-40 years
after the survivor was
infected initially. Muscle
weakness, joint pains and
fatigue are all health
problems that people with
post-polio syndrome tend to
experience. Symptoms range
from mild to severe. More
severe symptoms of post-
polio syndrome include
muscle weakness and
muscular atrophy being
more visible. Such symptoms
can make it more difficult for
the person to carry out day-
to-day tasks independently.
The Progression of Polio Disease
