This document discusses infection and infectious diseases. It defines infection as occurring when germs enter the body and multiply, causing disease. The four main types of infections are viral, bacterial, fungal, and parasitic. Common infectious diseases are then outlined, caused by viruses like the common cold and flu, or by bacteria like strep throat and E. coli. The document also discusses how infections are transmitted directly from person to person or indirectly through vectors, droplets, contaminated objects, food/water, animals, and the environment. Prevention methods include hand hygiene, immunizations, cough etiquette, cleaning, food safety, and social distancing.

1. INFECTION
BY
S.ILAYARAJA
MEDICAL AND SURGICAL
NURSING
SEA COLLEGE OF NURSING
BANGALORE

2. What is infection and its types?
Infection occurs when germs
enter your body and multiply,
resulting in disease. The four
main types of infections
are viral, bacterial, fungal,
and parasitic.

3. types
•Viral infections. Viruses are a piece of information (DNA or RNA) inside of a
protective shell (capsid). Viruses are much smaller than your cells and have no way to
reproduce on their own. They get inside your cells and use your cells’ machinery to
make copies of themselves.
•Bacterial infections. Bacteria are single-celled organisms with their instructions
written on a small piece of DNA. Bacteria are all around us, including inside of our
body and on our skin. Many bacteria are harmless or even helpful, but certain bacteria
release toxins that can make you sick.
•Fungal infections. Like bacteria, there are many different fungi. They live on and in
your body. When your fungi get overgrown or when harmful fungi get into your body
through your mouth, your nose or a cut in your skin, you can get sick.
•Parasitic infections. Parasites use the bodies of other organisms to live and reproduce
Parasites include worms (helminths) and some single-celled organisms (protozoa).
•Transmissible spongiform encephalopathies (TSEs/prion diseases). TSEs are
caused by prions — faulty proteins that cause other proteins in your body, usually in
your brain, to become faulty as well. Your body is unable to use these proteins or get
rid of them, so they build up and make you sick. Prions are an extremely rare cause of
infectious diseases.

4. Common infectious diseases caused
by viruses:
•Common cold.
•The flu (influenza).
•COVID-19.
•Stomach flu (gastroenteritis).
•Hepatitis.
•Respiratory syncytial virus (RSV).

5. Common infectious diseases
caused by bacteria:
Common infectious diseases caused by bacteria:
•Strep throat.
•Salmonella.
•Tuberculosis.
•Whooping cough (pertussis).
•Urinary tract infections (UTIs).
•E. coli.
•Clostridioides difficile (C. diff).

6. Who is most at risk for
getting infectious
diseases?
•Those with suppressed or compromised immune systems, such as
those receiving cancer treatments, living with HIV or on certain
medicines.
•Young children
•pregnant people and adults over 50.
•Those who are unvaccinated against common infectious diseases.
•Healthcare workers.
•People traveling to areas where they may be exposed to mosquitoes
that carry pathogens such as malaria, dengue virus and Zika viruses.

7. INFECTION TRANSMISSION
1.The Infectious Agent – or the microorganism which has the ability to cause
disease.
2.The Reservoir or source of infection where the microorganism can live and
thrive. This may be a person, an animal, any object in the general
environment, food or water.
3.The Portal of Exit from the reservoir. This describes the way the
microorganism leaves the reservoir. For example, in the case of a person
with flu, this would include coughing and sneezing. In the case of someone
with gastro-enteritis microorganisms would be transmitted in the faeces or
vomit.
4.The Mode of Transmission. This describes how microorganisms are
transmitted from one person or place to another. This could be via
someone’s hands, on an object, through the air or bodily fluid contact.

8. 1.The Portal of Entry. This is how the infection enters another individual.
This could be landing on a mucous membrane, being breathed in,
entering via a wound, or a tube such as a catheter.
2.The Susceptible Host. This describes the person who is vulnerable to
infection.
Infection can be prevented by breaking the Chain of Infection.

9. MODE OF TRANSMISSION
•Direct Transmission– This occurs when the pathogen is transmitted
directly from an infected person. For eg., if an open wound comes in
contact with the blood of a Hepatitis B infected patient, the wounded
person might contract the disease.
•Indirect Transmission- When the pathogens are not transmitted
directly from the infected person but through vectors such as flies,
mosquitoes, ticks, dogs, etc., it is known as indirect transmission.

10. Direct Transmission
1. Person to Person
When an infected person comes in contact with or exchanges body fluids with a non-infected person. A mother
can transmit infections to the unborn child via the placenta. A sexually transmitted disease such
as gonorrhoea can be transmitted by direct transmission.
2. Droplet Transmission
The droplets spread during sneezing, speaking, and coughing by an infected person can spread infections. The
infections can also spread by touching the nose and mouth with the hands contaminated with infectious
droplets. The droplets are so minute that they travel only a short distance before falling. The people nearby
might contract infections.
3. Spread by skin
There are a few infections such as chickenpox, conjunctivitis, head lice, ringworm, etc., which spread when the
skin of an infected person comes in contact with the skin of the other person.
4. Spread through body fluids or blood
A few diseases spread when the body fluids or blood of an infected person come in contact with the mucous
membrane or bloodstream of an uninfected person. Diseases such as hepatitis, HIV, cytomegalovirus
infections, etc. spread through semen and vaginal fluids, saliva, breastmilk, urine, etc.

11. Indirect Transmission
1. Airborne Transmission
Some infectious agents remain suspended in the air for a long period of time. These
pathogens might attack the immune system of a person in contact. E.g. if you enter a
room that was initially occupied by a patient of measles, you too might catch the
infection.
2. Contaminated Objects
The objects around us carry pathogens. Touching the infected objects which were initially
used by a diseased person might render us diseased. Contaminated blood and medical
supplies can also spread infections.
3. Vector-Borne Diseases
Some infectious agents are transmitted by the blood-sucking insects. The insects feed on
hosts such as birds, animals, and humans and carry infectious agents from them. These
infections are transmitted to some new host. Malaria and Lyme disease are the two
vector-borne diseases.

12. .Food and Drinking Water
Improperly canned and undercooked food is the main source of infections. Water also carries
various pathogens from rivers and lakes. It should be boiled or filtered before use. E.coli is
transmitted through contaminated food which causes various stomach problems. Botulism is
caused by the consumption of improperly canned food. Cholera is one water-borne disease which
has affected millions of people consuming contaminated water.
5.Transmission through Animals
When an infected animal bites or scratches against a person, it transfers the infectious agents to
the person. These agents can also be transmitted through animal waste. When diseases are
transferred from animals to people, zoonosis occurs. Anthrax (sheep), rabies (dogs), plague
(rodents) are some of the diseases transmitted from animals to humans. Pregnant women and
people with weak immune systems are more prone to infections.
6.Environmental Factors
The infectious agents are present in soil, water and plants as well. These agents can be
transmitted to people and may cause diseases. For eg., Hookworm is transmitted through
contaminated soil. Legionnaires’ disease is spread by water supplied to condensers and cooling
towers.

13. How can you prevent
infections?
You can help prevent the spread of infection by following these tips:
•Practice hand hygiene
•Keep up-to-date with immunization
•Practice cough and sneeze etiquette
•Clean surfaces regularly
•Keep sick children at home as much as possible
•Prepare food safely
•Practice safe sex
•Do not share personal belongings
•Travel wisely and maintain social distancing
Use masks and sanitizers frequently