Basic concept of infectious diseases | MPO training 16
Are you a Medical Promotion Officer (MPO) or planning to become one? This
article will help you understand the basic concept of infectious diseases in a
simple and practical way. You’ll learn how infections spread, common causes,
and ways to prevent them.
This knowledge is essential for MPOs to explain medicines to doctors more
effectively. Read this helpful guide to boost your skills. Stay informed, stay
prepared.
Table of contents: Basic concept of infectious diseases
Check out all the things you will learn about this topic here-
Basic concept of infectious diseases
The basic concept of infectious diseases includes understanding how germs
like bacteria and viruses cause illness. These infections can spread through
air, water, or contact. As a Medical Promotion Officer (MPO), you need to
know how these diseases work to promote the right medicine.
READ MORE: Concept microbiology guide | MPO training 15
This article explains it in simple terms. You’ll also learn how prevention
and treatment work. Stay ahead in your MPO journey with this clear and
useful guide.
What are infectious diseases?
Infectious diseases are illnesses caused by harmful organisms like
bacteria, viruses, fungi, or parasites that spread from one person to
another.
How do infectious diseases spread?
They can spread through air (like coughing), contact with infected people
or surfaces, water, food, or insect bites.
What are some common infectious diseases?
Some examples include the flu, COVID-19, tuberculosis, malaria, hepatitis
and dengue.
What are the symptoms of infectious diseases?
Symptoms vary, but common signs include fever, cough, sore throat, body
pain, fatigue, and sometimes diarrhea or rashes.
Infection
The invasion and growth of the pathogen in the body is called infection.
The pathogens may be bacteria, viruses, fungi, parasites etc.
Types of infectious diseases
- Bacterial infections: Bacteria are single-celled microorganisms. Bacteria are all around us, including inside our body and on our skin.
- Viral infections: Viruses are much smaller than our body cells and cannot reproduce independently. They get inside our cells and use the cells' machinery to make copies of themselves.
- Fungal infections: A fungal infection, also called mycosis. Generally, a skin disease caused by a fungus.
- Parasitic infections: Parasites use the bodies of other organisms to live and reproduce Parasites include worms (helminths) and some single-celled organisms (protozoa), lice etc.
Some Infection Related Definitions
Acute Infection: An infection characterized by sudden onset,
rapid progression and often with severe symptoms.
Chronic Infection: Any prolonged or persistent invasion of the
body by pathogens.
Primary Infection: An infection that develops in a healthy
individual.
Localized Infection: An infection that is restricted to a
specific location or region within the body of the host.
Systemic Infection: An infection that is in the bloodstream is
called a systemic infection.
Opportunistic infection: An infection caused by an organism
that does not normally cause disease. Opportunistic infections occur
in people with weakened immune systems.
Mixed infection: Infection with more than one kind of organism
at the same time is called mixed infection.
Epidemiology: The study of the transmission of disease.
Communicable Disease: A disease that can be transmitted from
one individual to another.
Contagious Disease: A communicable disease that is easily
spread from one individual to another.
Non-communicable Disease: A disease that is not transmitted
from one individual to another.
Endemic Disease: A disease condition that is normally found in
a certain percentage of a population.
Epidemic Disease: A disease condition present in a greater than
usual percentage of a specific population.
Pandemic Disease: An epidemic affecting a large geographical
area often on a global scale.
Bacterial Infections
Upper Respiratory Tract Infection (URTI)
| Infections | Description |
|---|---|
| Otitis Media | Inflammation of middle ear cavity |
| Sinusitis | Inflammation of sinus |
| Tonsillitis | Inflammation of tonsils |
| Pharyngitis | Inflammation of Pharynx |
| Laryngitis | Inflammation of Larynx |
- Otitis Media + Sinusitis: Causative Organisms = Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pyogenes.
- Tonsillitis + Pharyngitis + Laryngitis: Causative Organisms = Streptococcus pyogenes.
Lower Respiratory Tract Infection (LRTI)
| Infections | Description |
|---|---|
| Chronic Bronchitis | Inflammation of Bronchi |
| Pneumonia | Inflammation of lungs |
| AECB | Acute Exacerbation of Chronic Bronchitis |
| CAP | Community Acquired Pneumonia |
| HAP | Hospital Acquired Pneumonia |
- Chronic Bronchitis + Pneumonia + AECB + CAP + HAP: Causative Organisms = Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis.
Skin Infections
| Infections | Description |
|---|---|
| SSSIs | Skin and Skin Structure Infections |
- SSSIs: Causative Organisms = Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli.
Urinary Tract Infection (UTI)
| Infections | Description |
|---|---|
| Cystitis | Inflammation of urinary bladder |
| Pyelonephritis | Inflammation of kidneys |
| Urethritis (Non-Gonococcal Urethritis) | Inflammation of urethra |
| Urethritis | Inflammation of urethra |
| Gonorrhea |
Sexually transmitted infection
|
- Cystitis + Pyelonephritis: Causative Organisms = Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa.
- Urethritis (Non-Gonococcal Urethritis): Causative Organisms = Chlamydia trachomatis.
- Urethritis (Gonococcal Urethritis): Causative Organisms = Neisseria gonorrhoeae.
- Gonorrhea: Causative Organisms = Neisseria gonorrhoea.
(GI) Infection
| Infections | Description |
|---|---|
| Typhoid fever (Enteric fever) | Inflammation of small intestine, It causes high fever (104°F) & diarrhea. |
| Cholera | Water borne infection causing severe diarrhea and vomiting |
| Gastroenteritis | Inflammation of stomach and intestine |
| Dysentery | Inflammation of large intestine |
| Intra Abdominal Infections |
A group of infections that occur within the abdominal cavity
|
- Typhoid fever (Enteric fever): Causative Organisms = Salmonella typhi, Salmonella paratyphi.
- Cholera: Causative Organisms = Vibrio cholerae.
- Gastroenteritis: Causative Organisms = Escherichia coli, Shigella spp, Salmonella spp.
- Dysentery: Causative Organisms = Shigella spp.
- Intra Abdominal Infections: Causative Organisms = Escherichia coli, Klebsiella pneumonia, Bacteroides fragilis.
Bacterial Infections
| Infections | Description |
|---|---|
| Bacteremia | Presence of Bacteria in blood |
| Sepsis |
Severe infection of blood, It is Life threatening
|
| Septicemia |
Early stage of sepsis, May cause Septic shock &
Acute Respiratory Distress Syndrome (ARDS)
|
| Neutropenia | Abnormal low level of Neutrophils (WBC), This leads to further infections |
- Bacteremia + Sepsis + Septicemia: Causative Organisms = Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli.
- Neutropenia: Causative Organisms = Staphylococcus aureus.
CNS Infection
| Infections | Description |
|---|---|
| Meningitis | Inflammation of Meninges |
- Meningitis: Causative Organisms = Neisseria meningitidis, Haemophilus influenzae, Streptococcus pneumoniae.
Bone and Joint Infections
| Infections | Description |
|---|---|
| Bone and Joint Infections | Infection of bone and joints |
- Bone and Joint Infections: Causative Organisms = Staphylococcus aureus, Klebsiella spp, Enterobacter spp.
Infection of the Female Reproductive Organs
| Infections | Description |
|---|---|
| PID (Pelvic Inflammatory Disease) |
Inflammation of Uterus, Cervix, Fallopian tube &
Ovaries
|
- PID (Pelvic Inflammatory Disease): Causative Organisms = Neisseria gonorrhoeae.
Some Pronunciations in Bengali
- Chronic Bronchitis = ক্রনিক ব্রঙ্কাইটিস
- Acute Exacerbation of Chronic Bronchitis = একিউট এক্সাসারবেশন অফ ক্রনিক ব্রঙ্কাইটিস
- Community Acquired Pneumonia = কমিউনিটি একুয়ার্ড নিউমোনিয়া
- Cystitis = সিস্টাইটিস
- Pyelonephritis = পায়েলো নেফ্রাইটিস
- Pelvic Inflammatory Disease = পেলভিক ইনফ্লামেটরি ডিজিস
- Neutropenia = নিউট্রোপেনিয়া
- Gastroenteritis = গ্যাস্ট্রোএন্টেরাইটিস
Viral Infections
Influenza
It is a contagious respiratory illness caused by influenza
viruses that infect the nose, throat and sometimes the lungs. It
can cause mild to severe illness and at times can lead to death.
Influenza is commonly called the flu. Influenza viruses are
four types:
- Influenza A: Influenza A viruses cause seasonal flu epidemics & are the only type that can cause a pandemic. They can infect humans and animals. Bird flu and swine flu pandemics both resulted from Influenza A viruses.
- Influenza B: Influenza B viruses can also cause seasonal epidemics that typically only affect humans. Influenza B viruses mutate more slowly than Influenza A viruses.
- Influenza C: Influenza C viruses cause mild illnesses. They do not appear to cause epidemics.
- Influenza D: Influenza D viruses mainly affect cattle and do not seem to infect humans.
Symptoms of Influenza:
There are seven symptoms of influenza: fever, cough, sore throat,
runny nose, muscle/body Aches, headaches & fatigue.
Complications from flu:
The Most Common Flu complications include: pneumonia, bronchitis,
asthma, heart problems, ear infection & acute respiratory distress
syndrome.
Hepatitis
Hepatitis refers to inflammation of the liver. There are many causes of
hepatitis. Viral hepatitis is caused by a virus and can either be acute
(lasting less than six months) or chronic (lasting more than six
months). Viral hepatitis can be spread from person to person. Some types
of viral hepatitis can be spread through sexual contact.
Types of Hepatitis Virus
Hepatitis A: This form of hepatitis does not lead to chronic
infection and usually has no complications. The liver usually heals from
Hepatitis A within several months. Hepatitis A can be prevented by
vaccination. There is no cure, but treatment can help manage the
condition.
Hepatitis B: Infection with Hepatitis B is usually acute or
short-term, but it can become chronic, especially in children. Long-term
complications like liver cancer or cirrhosis can affect chronic
Hepatitis B. There is no cure, but treatment can help manage the
condition.
Hepatitis C: Hepatitis C is a blood-borne virus that usually
transmits through people sharing needles or other drug-related
equipment. It can be a short-term condition, but more than half of
people with Hepatitis C develop a chronic, long-term infection. It often
does not show any symptoms. No vaccine is yet available to prevent
Hepatitis C.
Hepatitis D: Hepatitis D is another viral hepatitis infection
that can be acute and chronic. As with other hepatitis infections, it
causes damage to a person's liver. However, these infections only occur
in people who already have Hepatitis B.
Long-term complications, such as liver cancer or cirrhosis, can affect
around 15-25% of people with chronic Hepatitis B. The Hepatitis D virus
cannot establish itself otherwise. If anyone is vaccinated against
Hepatitis B, he will be protected against the Hepatitis D virus.
Hepatitis E: This type of hepatitis is spread by ingesting
contaminated food or water. Hepatitis E is common throughout the world.
Fungal Infections
Candidiasis
Candidiasis is a fungal infection caused by a yeast (a type of fungus)
called Candida. Some species of Candida can cause infection in people;
the most common is Candida Falbicans. Candida normally lives on the skin
and inside the body, such as the mouth, throat, gut and vagina without
causing problems. Candida can cause infections if it grows out of
control or if it enters deep into the body.
Vaginal Candidiasis
Vaginal Candidiasis is a fungal infection that causes irritation,
discharge and intense itchiness of the vagina and the vulva (the tissues
at the vaginal opening).
Candida Infections of the Mouth, Throat and Esophagus
Candidiasis in the mouth and throat is also called Oral Thrush or
Oropharyngeal Candidiasis. Candidiasis in the esophagus is called
Esophageal Candidiasis or Candida Esophagitis. Candidiasis in the mouth
is called Oral Candidiasis.
Invasive Candidiasis
Invasive candidiasis is a serious infection that can affect the blood,
heart, brain, eyes, bones and other parts of the body by Candida.
Candidemia is the most common form of invasive candidiasis. It is a
bloodstream infection with Candida.
The most common symptoms of invasive candidiasis are fever and chills
that don't improve after antibiotic treatment for suspected bacterial
infections.
Tinea Infections
Tinea is the name of a group of diseases caused by dermatophytes
fungi. Dermatophytes are fungi that require keratin for growth. These
fungi can cause superficial infections of the skin, hair and nails.
Tinea Corporis
Tinea corporis is a superficial fungal infection of the skin that can
affect any part of the body, excluding the hands and feet, scalp, face
and beard, groin, and nails.
It is commonly called a 'ringworm' as it presents with characteristic
ring-shaped lesions.
Tinea Cruris
Tinea Cruris, also known as 'jock itch', is a specific form of tinea
infection that affects the groin, pubic region and adjacent thigh.
Tinea Capitis
Tinea capitis is a fungal infection of the scalp, involving both the
skin and hair. It is also known as a scalp ringworm. Symptoms of tinea
capitis include hair loss, dry scaly areas, redness and itch.
Tinea barbae is essentially the same condition involving the beard
area.
Tinea Pedis or Athlete's Foot
Tinea pedis or Athlete's Foot is a foot infection due to a
dermatophyte fungus. It is the most common dermatophyte infection and
is particularly prevalent in hot, tropical, urban environments.
Tinea Manuum
Tinea manuum is a fungal infection of the hand.
Tinea Unguium or Onychomycosis
Fungal infection of the nails. Symptoms include white or yellow nail
discolouration, thickening of the nail and separation of the nail from
the nail bed.
Onychomycosis
Onychomycosis is two types:
1. Finger Nail Onychomycosis
2. Toenail Onychomycosis
Aspergillosis
Aspergillosis is an infection caused by a type of mold (fungus)
called Aspergillus. The illnesses resulting from aspergillosis
infection usually affect the respiratory system, but their signs and
severity vary greatly.
Parasitic Infections
Intestinal Worm Infections
Intestinal worms, also known as parasitic worms, are one of the main
types of intestinal parasites in humans.
Most intestinal worm infections only cause mild illness and can be
treated with medication such as anthelmintic drugs.
- Hookworm infections: Hookworm infection is a roundworm infection of the intestines that can cause an itchy rash, respiratory and gastrointestinal problems, and eventually iron deficiency anemia due to ongoing loss of blood.
Hookworm is transmitted through larval penetration of the skin.
- Ascariasis infection: Ascariasis is an infection of the small intestine caused by Ascaris lumbricoides, which is a species of roundworm. Ascariasis generally occurs through hand-to-mouth ingestion of agricultural products or food contaminated with parasite eggs.
Amebiasis
Also known as amoebic dysentery, it is a serious parasitic
infection. This condition can cause abdominal pain, diarrhoea, and
bloody stools, or it may cause no symptoms at all. The parasite
that causes amebiasis only lives in humans and can spread through
faeces, infected food or water or sexual contact.
Giardiasis
It is a diarrheal disease caused by the microscopic parasite
Giardia duodenalis (or "Giardia" for short). Once a person or
animal has been infected with Giardia, the parasite lives in the
intestines and is passed in the stool. Once outside the body,
Giardia can sometimes survive for weeks or even months.
Scabies
Human scabies is a parasitic infection caused by Sarcoptes scabiei
var hominis. The microscopic mite burrows into the skin and lays
eggs, eventually triggering a host immune response that leads to
intense itching and rash.
FAQs related to Basic concept of infectious diseases
1. Can infectious diseases be prevented?
Yes, many can be prevented by vaccines, handwashing, wearing
masks, safe food practices, and avoiding contact with sick people.
2. What is the role of antibiotics in treating infectious
diseases?
Antibiotics help treat bacterial infections, but they do not work
on viruses. Misuse can lead to antibiotic resistance.
3. What is the difference between bacterial and viral
infections?
Bacterial infections are caused by bacteria and often treated with
antibiotics, while viral infections are caused by viruses and
usually go away on their own or need antiviral drugs.
4. What is infection control in hospitals?
It includes practices like hand hygiene, sterilization, and
isolation to stop infections from spreading in healthcare
settings.
5. When should you see a doctor for an infectious disease?
If symptoms are severe, long-lasting, or unusual, or if you're at
high risk (like elderly or children), you should see a doctor
immediately.
Conclusion
Infectious diseases are a major part of the healthcare world, and
knowing their basics is very important for any Medical Promotion
Officer (MPO). This article on the basic concept of infectious
diseases helps you learn how they spread, how they affect people,
and how you can explain them better to doctors. You now have a
simple yet clear idea about infections. Keep learning, because as
an MPO, your knowledge helps improve patient care. Stay focused
and stay confident.
Sarwar Hossain Himel
I am Sarwar Hossain Himel — a sports-loving person. Education: I have obtained a BBA and MBA degree in Accounting. Profession: Currently, I am working as a Medical Promotion Officer (MPO). In addition, I have over 5 years of experience in teaching. Freelance Work: I work as a Google Blogger and Article Writer in freelancing. Passion: I love doing web design and digital marketing. Especially, web design is one of my passions.