Health & Disease (Edexcel GCSE Biology: Combined Science)

• The World Health Organisation (WHO) defines health as 'a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity'
• This means that health is not just dependent on whether an individual is physically sick or not
  • There are lots of factors that should be considered when assessing the health of an individual which includes mental health as well as the level of social support in place

Communicable Diseases

• Communicable diseases are caused by microorganisms called pathogens which can spread between individuals or individuals and animals
  • E.g. chickenpox, a common childhood disease, is caused by a viral pathogen called the varicella-zoster virus whereas Covid-19 is caused by the SARS-CoV-2 virus

Communicable Diseases Table

Non-Communicable Diseases

• Non-communicable diseases are not caused by pathogens and cannot be passed on between individuals
  • Their effects on health tend to be longer-lasting; examples are asthma, CHD and most cancers

• However, the risk of developing non-communicable diseases may be increased by certain factors (including diet, stress and life situations) as these factors may have a profound effect on both physical and mental health
  • Eating a balanced diet that provides the right amount of energy and nutrients helps maintain good health whereas a poor diet can lead to deficiencies, obesity, diabetes and poor mental health
  • Constantly being under stress can lead to cardiovascular issues (such as high blood pressure, increasing the risk of CHD) and poor mental health
  • Where a person lives and their income can have a profound impact on health - this affects the standard of healthcare that is accessible to them (and what they can afford), what food they buy etc.

Risk Factors in Non-Communicable Diseases Table

• If an individual suffers from one disease, they are likely to be more susceptible to other diseases
• This is because the immune system may be compromised in some way or the different types of disease may interact in ways that negatively affect the health of the individual
  • Defects in the immune system mean that an individual is more likely to suffer from infectious diseases; individuals infected with HIV eventually end up with reduced numbers of lymphocytes circulating around the body which reduces the ability of the immune system to fight opportunistic infections like pneumonia
  • Viruses living in cells can be the trigger for cancers; the HPV virus can infect cells of the cervix in women resulting in cervical cancer developing in some cases, whereas some strains of the hepatitis virus can cause liver cancer
  • Immune reactions initially caused by a pathogen can trigger allergies such as skin rashes and asthma - these often develop as a result of an overactive immune response
  • Severe physical ill health can lead to depression and other mental illness; both can negatively impact the immune system and lifestyle choices made by the individual, further compounding the effects of poor health