Archives / july 2021

Dr. Sajitha Jasmin S L, MDS(OMR)

Epidemics such as H1N1, H5N1, avian influenza, Ebola, SARS, Zika, and Nipah have affected the world
in the past. The emergence of novel human pathogens is common in human history. A novel human
coronavirus initially named the Wuhan coronavirus (CoV), currently known as severe acute respiratory
syndrome coronavirus two (SARS- CoV-2) is responsible for the ongoing COVID 19 pandemic. On 30 th
January 2020, the WHO declared the outbreak of COVID-19 to be a Public Health Emergency of
International Concern because of its rapid spread across the world. There have been more than 42 million
people are infected and more than one million death as of date. As COVID 19 is an infectious disease, for
a better understanding of its nature, mode of infection, spread, signs and symptoms, preventive measures,
and treatment, we need to know about the common terms/ terminologies related to infectious diseases.

Disease: Disease means dis+ ease = not at ease. It can be 1. Infectious (Communicable) and 2. Non-
infectious (Non-communicable) diseases.
Infectious (Communicable) disease: A disease produced by an infection is called an infectious disease
Infection: The invasion of a host by disease-causing agents such as bacteria or virus and their
multiplication inside host tissues and the production of toxic products leads to the formation of disease
Infectious agent: Any microorganism capable of causing infection: eg. viruses, bacteria, prions, etc.
Communicable disease: A communicable disease is one that can be transferred from an infected
organism to an uninfected organism. The transmission of infection may be through direct or indirect
Direct transmission: Disease transmitted through touch, inhalation, sexual contact, contact with infected
body secretions, etc.
Indirect transmission: Through vectors like a mosquito. Example: Malaria, Dengue, etc. Vectors carry
and transfer the infectious agent into another living organism.
Fomite: An inanimate object or substance that transfers an infectious agent from one organism to another.
Example: Bedsheets, Sharing common objects, etc.
Aerosol: A tiny particle or droplet that’s suspended in the air.
Contagious disease: A communicable disease that spreads very quickly from one to another. Those with
contagious diseases are usually subjected to isolation or quarantine. Example: Measles, COVID 19
Isolation: The separation of a person with a contagious disease with others for the period of
communicability, that protects others from getting infected and thereby reduce the spread of disease.

Self-isolation: It’s a voluntary agreement stricter than quarantine. Also, it refers to staying in a contained area
or a single room alone to avoid infecting others.
Quarantine: The separation of a person from others for some period (incubation period, the period of
infectivity). Quarantine is the same as isolation, but the important difference between the two is, in
quarantine, it is not sure if the person is infected and hence segregate the suspected person for as long, as
it may take for the disease to ordinarily manifest itself after infection (incubation period). Once the
incubation period is over, we definitively know whether the organism was infected or not.
Incubation period: The time taken to manifest clinical symptoms to appear after infection.
Host: The organism harboring the infectious agent.
Asymptomatic: A disease stage in which the infected individual doesn't and will not exhibit symptoms
but can transmit the disease to others.
Exposed: “Exposed’ is used when the individual has encountered a pathogen.
Immunity: It refers to the individual’s resistance to infection or reinfection by a causative pathogen.
Immunity may be naturally acquired or vaccine-induced.
Herd immunity: The immunity of a group or community. The resistance of a group to invasion and
spread of an infectious agent, based on the resistance to infection of a high proportion of individual
members of the group.
Virus: Viruses are submicroscopic particles that can live and multiply only inside the living cells of an
Viral load: Also called viral dose, and it refers to the amount of virus exposed to. Someone who is exposed to
a relatively small amount of the virus might not get any symptoms
COVID-19: It stands for “coronavirus disease 2019.”
SARS-CoV-2: Severe acute respiratory syndrome coronavirus 2.
Respiratory disease. A disease that affects the lungs and other parts of the body involved with breathing.
Coronavirus is a respiratory disease.
Disease outbreak. A disease outbreak is the occurrence of disease cases above normal expectancy.
Endemic: It refers to the constant presence and/or usual prevalence of a disease or infectious agent in a
population within a geographic area. Malaria is endemic in some parts of Africa.
Epidemic: Epidemic is the sudden increase in the number of cases of a disease above what is normally
expected in that population in a geographical area.
Pandemic: It’s the epidemic that spread over several countries or continents, usually affecting a large
number of people. The World Health Organization declared coronavirus a pandemic on March 11. 

Super spreading is the transmission of infection to an unusually large number of individuals from a
single source or a person.
Super-spreader: One person who, for unknown reasons, can infect a large number of people.
Cluster:  A refers to an aggregation of cases in a particular area and time that are suspected to be greater
than the number expected.
Community spread is the spread of a communicable disease to people in a particular geographic area
who have no known contact with other diseased individuals.
Social distancing: Keeping a minimum distance between people. Measures are taken to minimize
contact between people, which can reduce the community spread of a contagious disease. Limiting the
size of gatherings is a primary social-distancing measure. 
Lockdown: A situation in which people are not allowed to enter or leave a building or area freely because
of an emergency
Mortality rate. The number of deaths by a disease divided by the number of confirmed cases.
Underlying condition. An existing health issue that impairs an individual’s resistance to another disorder
or disease. The underlying conditions that increase the risk of coronavirus disease are heart disease,
diabetes, respiratory illnesses, and immune system disorders.
Antigen: Any substance (e.g., a toxin or the surface of a microorganism or transplanted organ) is
recognized as foreign by the human body, and that stimulates the production of antibodies.
Antibody: It is also called immunoglobulin, a protective protein produced by the immune system in
response to the presence of a foreign substance, called an antigen.
Vaccine. A biological preparation provides immunity against one or several diseases by stimulating the
production of antibodies in the body.
Ventilator. A medical device that moves air into and out of the lungs of a patient who is physically
unable to breathe properly, the process is called artificial respiration.
Contact: In the context of communicable disease, a person or animal that has been in such association
with an infected person or animal or a contaminated environment and thus has had an opportunity to
acquire the infection.
Disinfection: Killing or inactivating infectious agents outside the body by direct exposure to chemical or
physical agents.
Sterilization:  It is the destruction of all microorganisms by physical heat, irradiation, gas, or chemical
Fumigation: The use of poisonous gas to remove harmful insects, bacteria, disease, etc.
from somewhere or something.

Hand hygiene: It’s a key strategy for slowing the spread of COVID-19. Washing hands with soap and
water, using alcohol hand rubs for at least 20 seconds is one of the most important steps to take to protect
against COVID-19 and many other diseases.
PPE: Personal protective equipment.

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