communicable diseases Flashcards
bbc bitesize
AIDS
definition
Acquired Immune Deficiency Syndrome – a disease of the human immune system caused by infection with Human Immunodeficiency Virus (HIV).
antibiotics
definition
Substance that controls the spread of bacteria in the body by killing them or stopping them reproducing.
What is antifungal medication?
Drugs that treat fungal infections like Athlete’s foot.
What is antimalarial medication?
Medicine that stops or treats a malarial infection
What are antivirals?
Drugs that prevent viruses replicating.
asthma
definition
A disease that affects the respiratory system.
What is athelete’s foot?
A rash caused by fungus growing on feet that can be treated by antifungal medication.
bacteria
definition
Single-celled microorganisms, some of which are pathogenic in humans, animals and plants. Singular is bacterium
carcinogen
definition
A chemical or other agent which causes cancer.
What is the cervix?
Ring of muscle at the lower end of the uterus
cystic fibrosis
definition
A disorder that mainly affects the lungs, pancreas, liver, and intestine. The main symptom is difficulty breathing.
cytoplasm
Definition
The living substance inside a cell (not including the nucleus)
What is a deficiency disease?
A disease that develops because an organism (plant or animal) does not have enough vitamins or mineral ions.
What is discharge?
Green or yellow liquid containing pus that arises from an infection.
What is disease?
Illness affecting plants and animals.
DNA
definition
Deoxyribonucleic acid. The material inside the nucleus of cells, carrying the genetic information of a living being.
What is ebola?
Often fatal disease caused by a virus which originated in Africa
What is the meaning of the term ‘eukaryotic’?
Description of a cell which has a nucleus. Eukaryotic cells also have other structures in the cytoplasm which have membranes around them.
fungi
definition
A large group of eukaryotic organisms that contain single celled yeasts, moulds and mushrooms
HIV
definition
Human Immunodeficiency Virus, a disease which damages cells in the immune system.
Host
definition
The organism lived on or in by a parasite.
immune system
definition
The body’s defence system against entry of any foreign body, including pathogens and agents such as pollen grains. The role of the immune system is to prevent disease.
What is the lytic pathway?
The process where a virus reproduces by infecting and then destroying a host cell
What are minerals?
Naturally occurring, inorganic chemical substances. Minerals are necessary for both plant and animal health
What is a norovirus?
A common ‘upset tummy’ infection caused by a virus which is highly contagious
nucleus
definition
The nucleus controls what happens inside the cell. Chromosomes are structures found in the nucleus of most cells. The plural of nucleus is nuclei.
prokaryote
definition
A single-celled organism which does not have a membrane-bound nucleus.
protein coat
definition
The proteins that surround the DNA of a virus.
protist
definition
A eukaryotic, usually single-celled organism of the kingdom Protista.
What is a stomach ulcer?
Open sores that develop on the lining of the stomach and are usually caused by bacteria.
What is transmission?
The spreading of pathogenic disease, for example by touch, food, water.
What is a vaccine?
Substances containing disabled antigens of a particular disease, usually administered via injection. Vaccines stimulate the body to produce antibodies to provide immunity against that disease.
vector
definition
A malaria-carrying mosquito.
virus
definition
An ultramicroscopic infectious non-cellular organism that can replicate inside the cells of living hosts, with negative consequences. plural viruses.
yeast
definition
A unicellular fungus used in the brewing and baking industries.
Health
The World Heath Organisation
The World Heath Organisation (WHO) is responsible for advising on ways to improve heath around the world. They define health as a state of complete physical, mental and social well-being. This means that being free from disease alone is not necessarily enough to be in good health.
Different types of diseases
Diseases can be grouped into two types:
- communicable, which can be transferred from one person to another, or from one organism to another, eg in humans, these include measles, food poisoning and malaria.
- non-communicable, which are not transferred between people or other organisms
Interactions between different types of diseases
Different types of disease may interact. This can mean that the presence of one disease can lead to a higher chance of developing another disease. Give examples of these.
- Defects in the immune system mean that an individual is more likely to suffer from infectious diseases. For instance, human immunodeficiency virus infections, known as HIV, which leads to AIDS, affect the immune system and lead to an increase in susceptibility to infectious diseases.
- Viruses living in cells can be the trigger for cancers. For instance, the majority of cases of cancer of the cervix are linked with a virus present in the female reproductive system.
- The reaction of the immune system to pathogens and other foreign bodies can trigger allergic reactions that lead to skin rashes and asthma. For instance, severe respiratory infections in babies can lead to asthma in later childhood.
- Severe physical ill health can lead to depression and other types of mental illness.
A pathogen is an organism that causes a disease. There are four main types of pathogen:
- Viruses
- Bacteria
- Fungi
- Protists
Examples of viruses; bacteria; fungi; protists in plants and animals.
- Viruses
in animals: HIV/AIDS
in plants: Tobacco mosaic virus - Bacteria
in animals: Salmonella
in plants: Agrobacterium - Fungi
in animals: Athlete’s foot
in plants: Black rose spot - Protists
in animals: Malaria
in plants: Downy mildew
Pathogens
All types of pathogen have a simple life cycle. They infect a host, reproduce themselves or replicate if it is a virus, spread from their host and infect other organisms. They also all have structural adaptations that make them successful at completing their life cycles, which enable them to cause more disease.
Diseases caused by pathogens are called communicable diseases. This means the disease can be transferred from an infected organism to another organism.
Pathogens
There are types of diseases which cannot be passed from organism to organism. These are called non-communicable diseases:
1) Inherited genetic disorders like cystic fibrosis can be passed to offspring but not to anyone else.
2) Deficiency diseases which are caused by a lack of essential vitamins or minerals, such as scurvy which occurs when an individual has insufficient vitamin C.
3) Diseases like cancer that develop as a result of exposure to carcinogens or develop naturally as cell division occurs incorrectly.
Pathogens
Transmission can occur in a number of important ways.
list types of transmission and examples of them.
Type of transmission: Direct contact
Example: This can be sexual contact during intercourse or non-sexual contact, like shaking hands.
Type of transmission: water
Example: Dirty water can transmit many diseases, such as the cholera bacterium.
Type of transmission: Air
Example: When a person who is infected by the common cold sneezes, they can spray thousands of tiny droplets containing virus particles to infect others.
Type of transmission: Unhygienic food preparation
Example: Undercooked or reheated food can cause bacterial diseases like Escherichia coli which is a cause of food poisoning.
Type of transmission: Vector
Example: Any organism that can spread a disease is called a vector. Many farmers think tuberculosis in their cattle can be spread by badgers.
Life cycle of a virus
The life cycle of a virus is the same as other pathogens. They can often survive outside a host for long periods of time. When they do infect a suitable host cell or cells, they replicate themselves within the cell thousands of times. They do not divide and reproduce like cells, but complete the lytic pathway.
Life cycle of a virus
step by step
1) They replicate their DNA and protein coats.
2) These are then assembled into new virus particles.
3) This causes the host cell or cells to burst. This is called lysis and provides the name of the ‘lytic cycle’.
4) Other nearby cells can then be infected with the virus. This process can be as quick as twelve hours in the case of the norovirus or several days for the process of Ebola.
Life cycle of a virus
Phages
Other types of virus called phages either join their DNA to that of their host or leave small circles of their DNA in the cytoplasm of their host cell or cells. This is called the lysogenic pathway. When these cells divide the DNA is copied. Later in the life cycle the viral DNA is copied and the lytic cycle detailed above begins.
Viral diseases
- Viruses are not alive because they do not complete all of the seven life processes, which are:
- Instead of species we say what?
- movement
- respiration
- sensitivity
- nutrition
- excretion
- reproduction
- growth
We say ‘strains’ of virus and not species. Strains are made of a relatively short length of genetic material (DNA) which is surrounded by a protein coat.
Viral infections cannot be treated by antibiotics.
Viral diseases
HIV
HIV stands for human immunodeficiency virus. This infection is transmitted by body fluids, often during unprotected sex, but also through cuts and injecting drugs using unsterilized needles. Immediately after infection, people often suffer mild flu-like symptoms. These pass and for a period of time infected people might not know they are infected.
Viral diseases
AIDS
AIDS stands for acquired immune deficiency syndrome. Months or years after the infection by HIV, the virus becomes active and attacks the patient’s white blood cells. HIV at this point has resulted in AIDS.
Viral diseases
Treatment of HIV/AIDS
There is no cure for HIV/AIDS although scientists are trying to find one. Currently, infected people are given antiviral drugs, which can significantly slow the development of AIDS.
Viral diseases
Ebola
In 2015 an outbreak of Ebola occurred in West Africa. Between 50% and 90% of Ebola cases are fatal. Early symptoms of Ebola include:
- fever and headache
- joint and muscle pain
- muscle weakness
Patients then develop diarrhoea, vomiting, stomach pain and internal bleeding.
Viral diseases
Transmission of ebola
The virus is transmitted in body fluids. It is possible to catch it from a dead person several days after they have died. It is also possible to catch it from the clothes or possessions of a dead person, having sex with an infected person or from unsterilized needles shared with an infected person.
There is currently no licensed treatment for Ebola.
Bacterial diseases
overview
Not all bacteria are pathogens which cause disease. Many bacteria, like those found in the intestines, are useful. All bacteria are prokaryotes, and do not have a nucleus. Unlike viruses, bacteria are cells and so are larger but cannot be seen without a microscope.
Bacterial diseases
Cholera
- Cholera is a bacterial infection often transmitted in dirty water or contaminated food. The symptoms of infected people include:
- symptoms
- treatment
- diarrhoea
- feeling and being sick (vomiting)
- stomach cramps
Having diarrhoea and vomiting mean infected people quickly become dehydrated and can go into shock. Large outbreaks of cholera are often found shortly after natural disasters or during armed conflict. Thousands of people currently die each year of cholera.
A vaccine prevents cholera infection. If infected, treatment involves taking oral rehydration solutions to prevent dehydration and shock. The solutions have salts and glucose in them to help replace those lost in diarrhoea and vomiting. Antibiotics are also used.
Bacterial diseases
Tuberculosis
- Tuberculosis (TB) is a bacterial infection spread in tiny droplets when a person coughs or sneezes. So it is an airbourne disease. Tuberculosis mainly infects the lungs where it causes damage. Symptoms include:
- Cause
- Treatment and prevention
- a bad cough often resulting in coughing up blood
- loss of appetite leading to weight loss
- high temperature
- tiredness and fatigue
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. Many healthy people have an immune system that is strong enough to kill any infecting bacteria. If patients have other diseases or a weakened immune system they are more likely to catch TB.
The BCG vaccine prevents infection with TB. If infected, antibiotics are prescribed.
Bacterial diseases
Stomach ulcers caused by Helicobacter
- causes
- symptoms
- risks
Helicobacter pylori is a bacterium which can cause stomach ulcers. It is a common infection and many people who are infected show no symptoms. The bacteria simply live in the stomach lining without causing ulcers. Transmission from an infected person is through saliva.
For some people, infection by H. pylori starts to irritate the lining of the stomach which then stops protecting them from the hydrochloric acid in their stomach. This irritation forms an ulcer. We don’t yet know why some people are more likely to develop ulcers.
Some lifestyle factors such as spicy food, stress, excessive alcohol and smoking can increase the risk of stomach ulcers.
Symptoms of stomach ulcers include:
- indigestion
- heartburn
- loss of appetite and weight loss
Antibiotics can be used to treat stomach ulcers shown to be caused by Heliobacter pylori.
Protist diseases
overview
Protists are a group of small organisms that have features that belong to animals, plants and fungi. They are a diverse group of organisms. Some are more like animals, others more like plants and some, called moulds, are closest to fungi. They are all eukaryotic, which means they have a nucleus.
Protist diseases
Spread of malaria
Malaria is spread by mosquitos, which carry the Plasmodium protist. These are often found in areas with higher temperatures like Africa, Asia, and South and Central America, but not the UK because of our lower temperatures. Mosquitos suck blood containing the protists from an infected person. They pass the protist, to other people they suck blood from. The mosquitos do not become ill and are called ‘vectors’ because they transmit the disease.
Protist diseases
Malaria symptoms and treatments
The symptoms of malaria include a fever, sweats and chills, headaches, vomiting and diarrhoea. Damage is also caused to the blood and liver. Of the 200 million people infected each year, up to half die from this disease. There is no vaccination for malaria. Infection can only be prevented by stopping individuals from being bitten. People sleep under mosquito nets and wear insect repellent to avoid bites. Antimalarial drugs are also taken, which treat the symptoms and can prevent infection.
Fungal diseases
overview
Not all fungi cause disease. Yeast is a single-celled fungus that is economically important because we use it to make things like bread and beer. Not all fungi are single-celled. Some such as mushrooms are multicellular and so much larger. These are still made of tiny cells like yeast, but have many more of them. Fungal cells have a nucleus and so are eukaryotic.
Fungal diseases
athlete’s foot
Athlete’s foot is a rash caused by a fungus that is usually found between people’s toes. It causes dry, red and flaky or white, wet and cracked skin. It is often found in communal areas like swimming pool changing rooms or gyms. It is transmitted by touching infected skin or surfaces that have been previous contaminated. It is treated by antifungal medication.
Fungal diseases
Chalara ash dieback
A species of fungus called Hymenoscyphus fraxineus infects ash trees. Infected plants suffer the following symptoms:
- leaf loss
- die back of new shoots
- bark lesions.
This species of pathogenic fungus is relatively new to the UK. It was first found in 2012. The fungus spreads through the air, so we call it an airborne infection. Since 2012 it has spread to about one third of all large woodlands in the UK.
Scientists are not yet sure how quickly this fungus will spread of what its full impact will be on our ash population. They are trying to identify the genetic factors that mean that some ash trees are naturally resistant to the fungus.
The transmission of pathogens can be prevented or reduced in a number of ways. There are a number of important methods of doing this. Name these methods, examples of the diseases they would be used for and how it works.
Method: Sterilising water
Example of disease: Cholera
How it works: Chemicals or UV light kill pathogens in unclean water.
Method: suitable food hygiene
Example of disease: Salmonella
How it works: Cooking foods thoroughly and preparing them in hygienic conditions kills pathogens.
Method: Suitable personal hygiene
Example of disease: Athlete’s foot
How it works: Washing surfaces with disinfectants kills pathogens. Treating existing cases of infection kills pathogens.
Method: Vaccination
Example of disease: Tuberculosis
How it works: Immunisations introduce a small or weakened version of a pathogen into your body, and the immune system learns how to defend itself.
Method: Contraception
Example of disease: HIV/AIDS
How it works: By using barrier contraception like condoms, it stops the transfer of bodily fluids and sexually transmitted diseases.
How would you prevent the transmission of the disease cholera. method and how it works.
Method: Sterilising water
How it works: Chemicals or UV light kill pathogens in unclean water.
How would you prevent the transmission of the disease salmonella. method and how it works.
Method: Suitable food hygiene
How it works: Cooking foods thoroughly and preparing them in hygienic conditions kills pathogens.
How would you prevent the transmission of the disease athlete’s foot. method and how it works.
Method: Suitable personal hygiene
How it works: Washing surfaces with disinfectants kills pathogens. Treating existing cases of infection kills pathogens.
How would you prevent the transmission of the disease tuberculosis. method and how it works.
Method: Vaccination
How it works: Immunisations introduce a small or weakened version of a pathogen into your body, and the immune system learns how to defend itself.
How would you prevent the transmission of the disease HIV/AIDS. method and how it works.
Method: Contraception
How it works: By using barrier contraception like condoms, it stops the transfer of bodily fluids and sexually transmitted diseases.
Sexually-transmitted infections
overview
Sexually transmitted infections (STIs) are passed from one person to another through sexual contact. This includes anal, oral or vaginal sex. There are more than 30 different pathogens that cause STIs. These include bacteria like Chlamydia and viruses like HIV. To reduce the spread of STIs people can abstain from sexual activity or use a barrier-type of contraception like a condom.
Sexually-transmitted infections
Chlamydia
Causes
Chlamydia is a sexually transmitted infection caused by a bacterium. It is a common infection, especially amongst people under 25. The NHS recommends that people who are under 25 and sexually active have a Chlamydia test every year or if they change partner.
Sexually-transmitted infections
Chlamydia
Symptoms and treatment
Chlamydia causes a burning pain when urinating and often forms a thick yellow or green discharge from an infected person’s penis or vagina. In women it can also cause bleeding between periods and men can develop swollen testicles.
If untreated, infection with Chlamydia can result in infertility. Like other bacterial infections, Chlamydia is treated by antibiotics.
What is the first step in the life cycle of a pathogen?
Infect a host
What type of pathogen causes cholera?
Bacterium
What type of pathogen causes tuberculosis?
Bacterium
