Communicable Diseases Flashcards
All 52 cards in this deck
What is a pathogen?
A microorganism that causes infectious (communicable) disease.
What four types of pathogen cause communicable disease?
Viruses, bacteria, protists and fungi.
Name three ways pathogens can be spread.
By direct contact, by water and by air.
How do bacteria make us feel ill?
They reproduce rapidly inside the body and produce poisons (toxins) that damage tissues.
How do viruses make us feel ill?
They live and reproduce inside cells, causing cell damage.
True or false? Communicable diseases can be passed from one organism to another.
True. They are caused by pathogens, which can be spread between animals or between plants.
What are the symptoms of measles?
Fever and a red skin rash.
How is the measles virus spread, and how is the disease controlled?
By inhalation of droplets from sneezes and coughs; most young children are vaccinated against it.
How is HIV spread?
By sexual contact, or by exchange of body fluids such as blood when drug users share needles.
What is late stage HIV infection (AIDS)?
When the immune system is so badly damaged it can no longer deal with other infections or cancers.
True or false? HIV infection causes no symptoms until the immune system is badly damaged.
False. It first causes a flu-like illness. Unless controlled with antiretroviral drugs, the virus then attacks the body's immune cells.
What symptom does tobacco mosaic virus (TMV) cause, and why does it reduce plant growth?
A distinctive 'mosaic' pattern of discolouration on the leaves, which reduces photosynthesis.
What are the symptoms of Salmonella food poisoning?
Fever, abdominal cramps, vomiting and diarrhoea, caused by the bacteria and the toxins they secrete.
How is Salmonella food poisoning spread?
By bacteria ingested in food, or on food prepared in unhygienic conditions.
How is the spread of Salmonella controlled in the UK?
Poultry are vaccinated against Salmonella.
What are the symptoms of gonorrhoea?
A thick yellow or green discharge from the vagina or penis, and pain on urinating.
How is gonorrhoea spread?
By sexual contact — it is a sexually transmitted disease (STD) caused by a bacterium.
How can the spread of gonorrhoea be controlled?
By treatment with antibiotics, or the use of a barrier method of contraception such as a condom.
True or false? Gonorrhoea is still easily treated with penicillin.
False. Many penicillin-resistant strains of the bacterium have appeared.
What type of pathogen causes rose black spot?
A fungus.
What are the symptoms of rose black spot?
Purple or black spots develop on the leaves, which often turn yellow and drop early.
How is rose black spot spread?
In the environment, by water or by wind.
How can rose black spot be treated?
By using fungicides and/or removing and destroying the affected leaves.
Why does rose black spot affect the growth of a rose plant?
Photosynthesis is reduced because the leaves are damaged and drop early.
What type of pathogen causes malaria?
A protist.
What is a vector?
An organism that passes a pathogen from one person (or organism) to another, e.g. the mosquito for malaria.
What are the symptoms of malaria?
Recurrent episodes of fever; it can be fatal.
How is the spread of malaria controlled?
By preventing the mosquito vectors from breeding, and by using mosquito nets to avoid being bitten.
True or false? Malaria is caused by the mosquito.
False. It is caused by a protist; the mosquito is the vector that carries the protist between people.
How does the skin defend the body against pathogens?
It acts as a barrier that stops pathogens entering, and forms scabs to seal cuts.
How does the nose defend the body against pathogens?
Hairs and mucus trap pathogens and particles in the air breathed in.
How do the trachea and bronchi defend the body against pathogens?
They secrete mucus that traps pathogens, and cilia waft the mucus up to the throat to be swallowed.
How does the stomach defend the body against pathogens?
It produces hydrochloric acid, which kills pathogens in swallowed mucus and food.
What are the three ways white blood cells defend the body against pathogens?
Phagocytosis (engulfing pathogens), producing antibodies, and producing antitoxins.
What is phagocytosis?
When a white blood cell engulfs and digests a pathogen.
What does vaccination involve putting into the body?
Small quantities of dead or inactive forms of a pathogen.
What are the steps by which vaccination makes a person immune?
e.g. the measles vaccine- A small quantity of dead or inactive pathogen is introduced — e.g. inactive measles virus.
- This stimulates white blood cells to produce antibodies.
- If the same pathogen re-enters, the white blood cells respond quickly to produce the correct antibodies, preventing infection.
How does immunising a large proportion of the population reduce the spread of a pathogen?
Far fewer people can catch and pass on the pathogen, so it spreads much less.
What happens to antibody production when the same pathogen enters the body a second time?
Antibodies are produced much more quickly and in much greater quantity.
True or false? A vaccine contains live, active pathogens that give you a mild form of the disease.
False. It contains small quantities of dead or inactive forms of the pathogen.
What are antibiotics?
Medicines that cure bacterial disease by killing infective bacteria inside the body, e.g. penicillin.
Why must a specific bacterial infection be treated with a specific antibiotic?
Each antibiotic only kills certain bacteria, so the correct one must be chosen for the disease.
True or false? Antibiotics can be used to treat flu.
False. Flu is caused by a virus, and antibiotics cannot kill viral pathogens.
What do painkillers and other symptom-relieving medicines do?
They treat the symptoms of disease but do not kill the pathogen.
Why is the emergence of antibiotic-resistant strains of bacteria of great concern?
The antibiotics available no longer kill those bacteria, so diseases become harder or impossible to treat and new antibiotics take time and money to develop.
Why is it difficult to develop drugs that kill viruses?
Viruses live and reproduce inside body cells, so drugs that kill them also damage the body's tissues.
Which plant does the heart drug digitalis originate from?
Foxgloves.
Which plant does the painkiller aspirin originate from?
Willow (willow bark).
Who discovered penicillin, and what was it obtained from?
Alexander Fleming, from the Penicillium mould.
What three things are new drugs extensively tested for?
Toxicity, efficacy and dose.
True or false? Claims about a new drug are more likely to be valid once they have been peer reviewed.
True. Peer review by other scientists checks the work before publication and helps detect false claims.
True or false? Preclinical testing of a new drug is carried out on healthy volunteers.
False. Preclinical testing is done in a laboratory using cells, tissues and live animals; healthy volunteers are used later, in clinical trials.