A protective protein produced by the immune system in response to the presence of a foreign substance, called an antigen. Antibodies recognise and latch onto antigens in order to remove them from the body. Antibodies are produced by specialised white blood cells called B lymphocytes (or B cells).

Source: antibody, Britannica 

An antiviral is a type of drug specifically designed to treat viral infections. Unlike antibiotics, which treat infections caused by bacteria, antivirals work against specific viruses by interfering with their ability to replicate or function. Antivirals can reduce symptoms and shorten the amount of time you are sick, reduce the risk of developing severe illness, and can also lower your risk of getting or spreading certain viruses. 

Source:  What Is an Antiviral?, National Foundation for Infectious Diseases  (NFID) 

Avian influenza, commonly known as bird flu, is a contagious viral disease caused by influenza A viruses which primarily infect wild birds and poultry. However, in rare cases, it may also infect humans and mammals. 

Source: Influenza - Avian, Communicable Diseases Agency Singapore

Coronavirus disease (COVID-19) is an infectious disease caused by SARS-CoV-2. Coronaviruses are a large family of viruses which may cause illness in animals or humans. In humans, several coronaviruses are known to cause respiratory infections ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS). 

Source: Coronavirus disease (COVID-19), WHO 

The coronavirus disease 2019 (COVID-19) pandemic is a global outbreak of coronavirus, an infectious disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Cases of novel coronavirus (nCoV) were first detected in China in December 2019, with the virus spreading rapidly to other countries across the world. This led WHO to declare a Public Health Emergency of International Concern (PHEIC) on 30 January 2020 and to characterise the outbreak as a pandemic on 11 March 2020.

Source: Coronavirus disease (COVID-19) pandemic, WHO 

Diabetes is a chronic, metabolic disease characterised by elevated levels of blood glucose (or blood sugar), which leads over time to serious damage to the heart, blood vessels, eyes, kidneys and nerves. 

Source: Diabetes, WHO

Diagnostics in respiratory viruses refers to the use of laboratory tests to detect and confirm viral infections in the respiratory tract by identifying viral genetic material, antigens, or other markers in patient samples. 

Source: Testing and Respiratory Viruses, CDC

Epidemiology in respiratory viruses is the scientific study of how respiratory viral infections spread and affect populations, and how that information is used to control and prevent disease 

Source: Glossary, CDC

H5N1 is one of several influenza viruses that causes a highly infectious respiratory disease in birds called avian influenza (or "bird flu"). Infections in mammals, including humans, have also been documented. 

Source: Influenza: A(H5N1), WHO

Human metapneumovirus (hMPV) is a virus that usually causes symptoms similar to a cold. You might cough or wheeze, have a runny nose or a sore throat. Most cases are mild, but young children, adults over 65 and people with weakened immune systems are at a higher risk for serious illness. 

Source: Human Metapneumovirus (HMPV): Symptoms & Treatment

Immunology is the study of the immune system and is a very important branch of the medical and biological sciences. The immune system protects us from infection through various lines of defence. If the immune system is not functioning as it should, it can result in disease, such as autoimmunity, allergy and cancer. It is also now becoming clear that immune responses contribute to the development of many common disorders not traditionally viewed as immunologic, including metabolic, cardiovascular, and neurodegenerative conditions such as Alzheimer’s.

Source: What is immunology?, British Society for Immunology

Seasonal influenza (the flu) is an acute respiratory infection caused by influenza viruses. It is common in all parts of the world. Most people recover without treatment.  Influenza spreads easily between people when they cough or sneeze. Vaccination is the best way to prevent the disease. Symptoms of influenza include acute onset of fever, cough, sore throat, body aches and fatigue.

Source: Influenza, WHO