A Helpful Glossary of Terms


A family of viruses, seven of which are known to infect people. They get their name from the crown-like spikes—coronas—that appear on the viruses under a microscope. Coronaviruses can cause the common cold (which can also be caused by other viruses, such as rhinoviruses), as well as dangerous illnesses such as severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS). SARS CoV-2, the coronavirus virus first discovered in December 2019, causes the disease now known as COVID-19.

COVID-19 (Coronavirus Disease 2019)

In the same way that human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome (AIDS), the coronavirus SARS-CoV-2 causes COVID-19. The symptoms of COVID-19 include cough, fever, and shortness of breath. While the disease appears to cause mild to moderate illness in most people, in others it has caused life-threatening pneumonia and death. Doctors and researchers continue to learn more about the disease, so information about symptoms, prevention, and treatment may change as more data becomes available.

SARS (Severe acute respiratory syndrome)

A coronavirus, which first infected humans in 2002, that reached epidemic proportions before it was contained: there have been no outbreaks since 2003. SARS causes fever, headache, body aches, a dry cough, hypoxia (oxygen deficiency), and usually pneumonia. SARS and SARS CoV-2 are related genetically, but the diseases they cause are different.

SARS-CoV-2 (Severe acute respiratory syndrome coronavirus 2)

The new coronavirus that causes COVID-19, which is believed to have started in animals and spread to humans. Animal-to-person spread was suspected after the initial outbreak in December among people who had a link to a large seafood and live animal market in Wuhan, China. While no one knows for sure how SARS-CoV-2 spread from an animal (and what type of animal) to a human, SARS-CoV-2 is a betacoronavirus, which means it originated in bats. 

A simple A-Z of terms you might need to know

Airborne transmission

The spread of infection from one person to another by airborne particles containing infectious agents.

Airborne particles

Very small particles that may contain infectious agents. They can remain in the air for long periods of time and can be carried over long distances by air currents. Airborne particles can be released when a person coughs or sneezes, and during aerosol generating procedures (AGPs).

Airborne precautions

Measures used to prevent and control infection spread through airborne transmission without necessarily having close contact with another person.

Antibody Test

You may hear it called a serology test.

The antibody test isn’t checking for the virus itself. Instead, it looks to see whether your immune system — your body’s defence against illness — has responded to the infection.

Immunoglobulin A: IgA antibodies are found in the mucous membranes of the lungs, sinuses, stomach, and intestines. They’re also in fluids these membranes produce, like saliva and tears, as well as in the blood.

Immunoglobulin G: IgG is the most common type of antibody in your blood and other body fluids. These antibodies protect you against infection by ‘remembering’ which germs you’ve been exposed to before.

If those germs come back, your immune system knows to attack them. You can test for IgG to find out whether you’ve been infected by certain kinds of bacteria or virus.

Immunoglobulin M: Your body makes IgM antibodies when you are first infected with new bacteria or other germs.

They are your body’s first line of defence against infections. When your body senses an invader, your IgM level will rise for a short time. It will then begin to drop as your IgG level kicks in and increases to protect you in the longer term.

Anti-viral medicines

A class of drugs used to treat viral infections—not bacterial ones (which are treated with antibiotics). So far there are no specifically approved drugs to treat COVID-19, but scientists are studying drugs approved for other diseases. There are also several investigational, or experimental, drugs being studied in several hundred clinical trials currently underway in countries around the world.


When a patient is a carrier of an illness but does not show symptoms. People are thought to be most contagious for COVID-19 when they are most symptomatic, according to the CDC, although researchers are still investigating how its spread might be possible at other times, including during the incubation period (called ‘pre-symptomatic transmission’) and even after symptoms have resolved.

CE marking

CE marking is a certification mark that indicates conformity with health, safety, and environmental protection standards for products sold within the European Economic Area. The CE marking is also found on products sold outside the EEA that have been manufactured to EEA standards.


A collection of cases occurring in the same place at the same time.

Community spread

Circulation of a disease among people in a certain area with no clear explanation of how they were infected—they did not travel to an affected area and had no close link to another confirmed case. This is sometimes referred to as community transmission.

Contact precautions

Measures used to prevent and control infections that spread via direct contact with the infected person or indirectly from their immediate environment. This is the most common route of infection transmission.

Contact transmission

Contact transmission is the most common route of transmission, and consists of two distinct types: direct contact and indirect contact. Direct transmission occurs when microorganisms are transmitted directly from an infectious individual to another individual without the involvement of another contaminated person or object. Indirect transmission occurs when microorganisms are transmitted from an infectious individual to another individual via a contaminated object or person or person.


Continuous positive airway pressure is a form of positive airway pressure ventilator, which applies mild air pressure on a continuous basis. It keeps the airways continuously open in people who are able to breathe spontaneously on their own, but need help keeping their airway unobstructed.

Drive-through testing

Medical staff will take a ‘swab test’ (usually done through the nose) to collect cells to test for COVID-19. These designated testing stations reduce the likelihood of further spreading the illness by allowing you to remain in your car, having the test taken through your open window. The sample is then sent to a laboratory.


The baseline, or expected, level of the disease in the community—meaning it always exists, like the common cold and flu, which are usually at low, predictable rates.


This refers to a sudden increase in the number of cases of a disease, above what is typically expected in a particular area. COVID-19 is thought to have reached epidemic proportions in China in mid-January.

Flattening the curve

Slowing the spread of the virus. If you map the number of COVID-19 cases over time, the expectation is that it will peak at some point—on a graph this peak would mirror a surge in hospital patients. ‘Flattening the curve’, which involves strategies to decrease transmission of the disease, would result in fewer patients during that peak period. This, in turn, would mean hospitals would be better able to manage the demands of patients who have COVID-19 and other illnesses.

Frequently touched surfaces

Surfaces of the environment which are commonly touched or come into contact with human hands.

Hand hygiene

A key strategy for slowing the spread of COVID-19. Washing hands with soap and water for at least 20 seconds is one of the most important steps you can take to protect against COVID-19 and many other diseases.

Healthcare or clinical waste

Waste produced as a result of healthcare activities for example soiled dressings, sharps.

Incubation period

The time between when a person is infected by a virus and when he or she notices symptoms of the disease. Estimates of the incubation period for COVID-19 range from 2-14 days, but doctors and researchers may adjust that as more data becomes available.


The ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells. Research is ongoing about immunity to COVID-19 following initial infection.

Long term health condition

This covers:

  • chronic obstructive pulmonary disease, bronchitis, emphysema or asthma
  • heart disease
  • kidney disease
  • liver disease
  • stroke or a transient ischaemic attack (TIA)
  • diabetes
  • lowered immunity as a result of disease or medical treatment, such as steroid medication or cancer treatment
  • a neurological condition, such as Parkinson’s disease, motor neurone disease, multiple sclerosis (MS), cerebral palsy, or a learning disability
  • any problem with the spleen, including sickle cell disease, or had spleen removed
  • a BMI of 40 or above (obese)


The Medicines and Healthcare products Regulatory Agency is an executive agency of the Department of Health and Social Care in the United Kingdom which is responsible for ensuring that medicines and medical devices work and are acceptably safe.


This shares the same definition as epidemic, with one exception—an outbreak usually refers to a more limited geographic area. COVID-19 started as an outbreak in Wuhan, the capital city of the Hubei province in China at the end of December 2019, when the Chinese government confirmed that it was treating dozens of cases of pneumonia of unknown cause.  


An epidemic that has spread over several countries or continents, affecting many people. Pandemics typically happen when a new virus spreads easily among people who—because the virus is new to them—have little or no pre-existing immunity to it. COVID-19, which was declared a pandemic by the WHO in early March, is the first pandemic known to be caused by the emergence of a new coronavirus. 

The Centers for Disease Control in the US describes the recognizes six stages to a pandemic in an easy to understand way. A pandemic starts with an investigation phase, followed by recognition, initiation, and acceleration phases, which is when it peaks. Then, comes a deceleration phase, when the rate of infection decreases. Finally, there is a preparation phase, where the pandemic has abated, and public health officials monitor virus activity and prepare for possible additional waves of infection. Different countries—and various sections of the same country—can be in different phases of the pandemic at the same time.

Personal protective equipment (PPE)

In healthcare settings, PPE might include gloves, gowns, aprons, masks, respirators, goggles, and face shields.

Typically, and in a pre-COVID-19 world, health care workers use new PPE for each patient interaction, depending on the patient’s condition, which is why with the expected surge of COVID-19 patients, the supply of PPE in hospitals around the country is expected to run low—or out.

PCR test

Polymerase chain reaction (PCR) is a method used widely in molecular biology to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to take a very small sample of DNA and amplify it to a large enough amount to study in detail.

Public Health England (PHE)

PHE is responsible for:

  • making the public healthier and reducing differences between the health of different groups by promoting healthier lifestyles, advising government and supporting action by local government, the NHS and the public
  • protecting the nation from public health hazards
  • preparing for and responding to public health emergencies
  • improving the health of the whole population by sharing our information and expertise, and identifying and preparing for future public health challenges

Professional Use

For use by trained healthcare professionals or those who have undertaken product-specific training


Quarantine involves separating and restricting the movements of people who were exposed to a contagious disease to see if they become ill. The government may impose a quarantine on someone who was exposed to COVID-19 to avoid spread of the disease to others.

Respiratory symptoms

Respiratory symptoms include:

  • rhinorrhoea (runny nose)
  • sore throat
  • cough
  • difficulty breathing or shortness of breath


This is a more severe form of social distancing and applies to people who have symptoms of coronavirus. They should remain indoors as much as possible and avoid contact with other people including those in their own home if they are yet to show symptoms. This period should last for seven days but anyone living with symptomatic people should self-isolate for 14 days because of the length of time it takes for the virus to incubate and show symptoms.


This simply means checking yourself for COVID-19 symptoms, including fever, cough, or difficulty breathing. If you notice symptoms, you should self-isolate and seek advice by telephone from a health care provider or NHS111 to determine whether you need a medical evaluation.


Shielding is a practice used to protect extremely vulnerable people from coming into contact with coronavirus. This applies to 1.5m vulnerable or elderly people with other health conditions. They should not go outside for 12 weeks, even to buy food. The army is supplying them with essentials.

Social distancing

Measures to limit person-to-person interactions to prevent infection. This includes people staying at least two metres away from each other in supermarkets, on public transport and among family members they may not live with. The government has imposed restrictions designed to enforce social distancing, which include working from home, closing schools, and shutting shops, restaurants and cinemas etc. People can only leave their homes for essential purposes such as buying food and to take one form of exercise each day. Police will have the powers to fine people and to disperse groups of more than two people.


One person who, for unknown reasons, can infect an unusually large number of people. Infectious disease specialists say it is common for super-spreaders to play a large role in the transmission of viruses. In what’s known as the 80/20 rule, 20% of infected patients may drive 80% of transmissions.


Although scientists are still learning about COVID-19 as more data becomes available, the virus is thought to be spread mainly from person-to-person contact, as well as when a person touches a surface or object that has the virus on it and then touches the mouth, nose, or possibly eyes.

Droplet transmission

A form of direct transmission, this is a spray containing large, short-range aerosols (tiny particles suspended in air) produced by sneezing, coughing, or talking. Droplet transmission occurs—in general and for COVID-19—when a person is in close contact with someone who has respiratory symptoms.


A vaccine triggers the immune system to help it build immunity to a disease. The immune system already has the capacity to react to diseases by producing substances called antibodies that remain in the body to fight them in the future. With a vaccine, you don’t have to get the disease to develop immunity—the vaccine triggers the same process by providing the body with a tiny amount of a germ that has been weakened or killed, but small enough that it won’t make you ill. Vaccines are introduced to the body via injection, mouth, or a nasal spray.


This is a machine to help patients breathe when their lungs are damaged, and they can’t get enough oxygen on their own. A ventilator takes over the work of breathing for a patient to allow the damaged lungs to heal; it is not itself a treatment.

WHO (World Health Organisation)

The World Health Organisation is a specialised agency of the United Nations responsible for international public health working across 150 countries.