Infection and Response

• What is a pathogen?

  A pathogen is a microorganism that causes disease.
• What is a communicable disease?

  A communicable disease is a disease that can be spread from person to person.
• What are the four main types of pathogens?


  The four main types of pathogens are viruses, bacteria, fungi and protists.
• How are communicable diseases spread?


  Communicable diseases can be spread by:

  1: Water - drinking or bathing in contaminated water e.g. cholera

  2: Air - pathogens are carried through the air in water droplets produced from coughs and sneezes e.g. the flu

  3: Direct contact - touching contaminated surfaces e.g. Athlete's foot
• How can the spread of communicable diseases be prevented?


  The spread of communicable diseases can be prevented in 4 main ways:

  1) Being hygienic e.g. washing hands before preparing/cooking food or after sneezing, wearing condoms, filtering & boiling water etc.

  2) Destroying the vectors of diseases or their habitats.

  3) Isolating infected individuals - inc. social distancing and wearing masks.

  4) Vaccination - both of the general populace and of animals that will be eaten.
• How do bacteria make us feel ill?

  Bacteria make us feel ill buy producing toxins, which damage our cells.
• What do bacteria need in order to multiply?


  In order to multiply, bacteria need nutrients (e.g. carbohydrates, proteins, minerals and vitamins), moisture, warmth and time.
• Describe how multicellular fungi can cause diseases.


  Multicellular fungi have a body which is made up of hyphae (thin thread-like structure). These hyphae can grow and penetrate human skin and the surface of plants, which can cause diseases. They can also produces spores, which can be spread to other plants and animals.
• How is gonorrhoea spread?


  Gonorrhoea is a STD, so transmitted through sexual contact or to a baby at birth.
• What are the symptoms of gonorrhoea?


  The symptoms of gonorrhoea are painful urination and a thick greenish-yellow discharge from the penis or vagina.
• How can gonorrhoea be treated?


  Gonorrhoea can be treated with penicillin (an antibiotic) but there are resistant strains.
• How is salmonella spread?

  Salmonella is spread through contaminated food, typically chickens and eggs.
• What are the symptoms of salmonella?


  The symptoms of salmonella include fever, abdominal cramps, vomiting and diarrhoea.
• How can salmonella be prevented?


  Salmonella can be prevented by vaccinating chickens and good food hygiene (cooking the meat/eggs).
• How can salmonella be treated?


  The body's immune system usually manages salmonella itself, but antibiotics can be necessary if the symptoms persist for more than a week. Electrolytes can also be used to help ease dehydration.
• How big are bacteria cells?

  Bacterial cells are generally between 0-30 micrometers.
• How big are viruses?

  Viruses are generally between 10-100 nanometers.
• How do viruses reproduce?

  Viruses can only reproduce inside of other host cells.
• How do viruses damage cells?


  They inject their own DNA into the host cell, taking it over, and eventually bursting it and releasing the viruses inside.
• What pathogen causes measles?


  Measles is caused by a virus
• What are the symptoms of measles?


  The symptoms of measles include red skin rash and a fever. Complications can cause blindness, brain damage and even death.
• How is measles spread?

  Measles can be spread by the inhalation of water droplets from sneezes and coughs.
• What pathogen causes HIV?


  HIV (human immunodeficiency virus) is caused by a virus.
• What are the symptoms of HIV?


  The symptoms of HIV are initially flu-like, but in late stages (AIDS - acquired immunodeficiency syndrome) the immune system is compromised, leaving the body open to attacks from other conditions.
• How is HIV spread?


  HIV is spread through sexual contact, or through the exchange of body fluids such as blood when drug users share needles or in breast feeding.
• How can HIV be prevented?


  HIV can be prevented through the use of condoms, blood screening, needle replacement services and bottle feeding.
• How can HIV be treated?


  Antiretroviral drugs can prevent HIV, but not cure it.

  Good health can help prevent the onset of AIDS for people that already have HIV.
• What pathogen causes tobacco mosaic virus?


  Tobacco mosaic virus is caused by a virus.
• What are the symptoms of tobacco mosaic virus?


  The symptoms of tobacco mosaic virus include a distinctive 'mosaic' pattern of discolouration on the leaves.
• How is tobacco mosaic virus spread?

  Tobacco mosaic virus is spread by contact between infected and healthy plants. Insects may act as vectors which transfer the virus between different plants.
• How can tobacco mosaic virus be prevented?


  Tobacco mosaic virus can be prevented by good hygiene, pest control, farmers growing TMV-resistant strains of plants.
• What pathogen causes rose black spot?

  Rose black spot is caused by a fungus.
• What are the symptoms of rose black spot?

  The symptoms of rose black spot include purple or black spots that develop on leaves, which then turn yellow and drop early, resulting in less flowers and growth.
• How is rose black spot spread?

  Rose black spot is spread by spores which are spread by wind and rain.
• How can rose black spot be treated/prevented?


  Rose black spot can be treated by removing/burning infected leaves and/or isolating plants.
• Define parasite.


  An organism which lives on and feeds on another organism and causes it harm.
• What pathogen causes malaria?


  Malaria is caused by a protist (plasmodium, which is a parasite).
• How is malaria spread?


  Malaria is spread by mosquitoes (the female anopheles mosquito, which is a type of vector).
• What are the symptoms of malaria?

  The symptoms of malaria include fever, shaking, and death.
• What is the prognosis of malaria?


  Without expensive care, malaria is fatal: 660 000 deaths annually, mainly in third-world countries.