Pathogens, Disease and Transmission - Transmission of Disease (GCSE Biology)

Transmission of Disease

Controlling Spread of Pathogens

Spreading of Pathogens

Pathogens can be spread in different ways:

• Water – infection is spread in water contaminated by pathogens. It can be spread by bathing in, or by ingesting this water. Cholera is spread like this, as the water is contaminated by the faeces of the patients.
• Direct contact – direct contact with sufferers e.g. through blood or body fluids, can spread disease. The type of direct contact will determine whether the pathogen will spread – for example, chicken pox can spread just by touching, whereas HIV requires sexual contact for spreading.
• Indirect contact – indirect contact with sufferers e.g. through contaminated surfaces, food soil or air for example, touching a surface that a person has sneezed on.
• Air – infections spread by water are called droplet infections. Droplet infections are spread in the air through coughs and sneezes. A very common example of this is influenza, the common flu, which can spread from person to person.

Social and Economic Factors Affecting the Spread of Disease

• Crowding can increase disease transmission. When a lot of people are confined in a small place, it is easier for a disease to spread from one person to another.
• A poor diet can lead to a weakened immune system. This can increase the risk of infection and thus, increase the spread of the infection.
• Limited access to health education and healthcare can increase the risk of infection. Without access to health education, diseases e.g. sexually transmitted infections, can spread. Similarly, without access to healthcare, diagnosis and treatment can be delayed or the disease can spread to others.

Sampling

• You can estimate the number of infected individuals in a population by sampling. You would take some samples of the population and work out the mean number of infected individuals. Then multiply the mean by the total number of individuals in the population.