Cardiovascular diseases (CVDs) are a group of disorders of the heart and blood vessels. Heart attacks and strokes are usually acute events and are mainly caused by a blockage that prevents blood from flowing to the heart or brain. The most common reason for this is a build-up of fatty deposits on the inner walls of the blood vessels that supply the heart or brain.

Source: Cardiovascular diseases (CVDs), WHO.

A young human being below the age of puberty or below the legal age of majority. For many young children with flu, it is the first time they are exposed to the virus. Their immune system is naïve to influenza and therefore responds more slowly to the infection. This means the influenza virus can cause significant ill-effects before the immune system can bring it under control.

Source: Kids are more vulnerable to the flu – here’s what to look out for this winter, National Centre for Immunisation Research and Surveillance (NCIRS)

A chronic lung disease (CLD) is a type of disease that prevents the lungs and respiratory system from working correctly. Chronic lung diseases often develop slowly but may get worse over time. Causes and risk factors may include smoking or having a smoking history, genetics or family history, work-related exposures, secondhand smoke, air pollution or frequent childhood lung infections.

Source: Chronic Lung Disease, American Lung Association.

Diabetes is a condition that happens when your blood sugar (glucose) is too high. It develops when your pancreas doesn’t make enough insulin or any at all, or when your body isn’t responding to the effects of insulin properly. Diabetes affects people of all ages. Most forms of diabetes are chronic (lifelong), and all forms are manageable with medications and/or lifestyle changes. There are several forms of diabetes. Type 2 is the most common.

Source: Diabetes: What It Is, Causes, Symptoms, Treatment & Types, Cleveland Clinic.

Healthcare workers refer to individuals from various professions involved in the health sector, including clinical workers such as physicians and nurses, as well as managers, pharmacists, supply chain workers, ambulance drivers and community health volunteers.

Source: Health Care Worker - an overview | ScienceDirect Topics.

Immunocompromised is a condition where your immune system isn’t working as well as it should. This means you can’t fight off infections as well and you could get sick more often or more severely than someone who isn’t immunocompromised. Diseases, medications and organ or bone marrow transplants can compromise your immune system.

Source: Immunocompromised: Immunosuppressed, Definition & Diseases List, Cleveland Clinic.

A mental disorder is characterised by a clinically significant disturbance in an individual’s cognition, emotional regulation or behaviour. It is usually associated with distress or impairment in important areas of functioning. There are many different types of mental disorders. Mental disorders may also be referred to as mental health conditions.

Source : Mental disorders, WHO.

Neurological disorders are conditions that target how your nervous system (brain, spinal cord and nerves) functions. There are hundreds of neurological disorders like Alzheimer’s disease, multiple sclerosis and meningitis, for example. They cause symptoms that affect how you move, think and feel. Treatment options vary based on the type.

Source: Neurological Disorders, Cleveland Clinic.

Noncommunicable diseases (NCDs), commonly known as chronic or lifestyle-related diseases, are diseases that are not infectious to others. NCDs tend to be of long duration and are the result of a combination of genetic, physiological, environmental and behavioural factors. The main NCDs are cardiovascular diseases (like heart attacks and stroke), cancers, chronic respiratory diseases (such as chronic obstructed pulmonary disease and asthma), and diabetes. NCDs are the world’s biggest killers and a leading cause of death in the Region. Other NCDs include: hypertension, Alzheimer's and osteoporosis.

Source: Noncommunicable diseases, WHO.

As people get older, their immune systems can change and weaken over time, which can increase the risk for complications from respiratory illnesses. Older adults are also more likely to have underlying health conditions. Most deaths from respiratory viruses occur in people older than 65, with risk increasing sharply with advancing age.

Source: People at Increased Risk for Severe Respiratory Illnesses, CDC.

Seasonal influenza affects up to 11% of pregnant women annually, and accounts for a considerable number of hospitalisations and deaths during gestation. Pregnant women are susceptible to more severe influenza infections owing to physiologic changes that affect cardiopulmonary function and cell-mediated immunity, with data suggesting that gestational influenza infection is associated with preterm birth and stillbirth.

Source: Risk of severe influenza infection in women with a history of pregnancy complications: A longitudinal cohort study | PLOS One, Public Library of Science (PLOS).