Biology - infection and response

What are communicable diseases?

Diseases that can be spread from person to person or between animals and people.

What are communicable diseases caused by?

pathogens

What is a pathogen?

A microorganism that causes disease

How do communicable diseases spread?

- Direct contact

- Indirect contact

- Airborne transmission

- Vector-borne transmission

- Food and water-borne transmission

How can diseases spread from direct contact?

By touching an infected person, kissing, sexual contact, or coming into contact with bodily fluids

How can diseases spread from indirect contact?

By touching contaminated surfaces

How can diseases spread through airborne transmission

By inhaling droplets from coughing, sneezing or talking

How can diseases spread through vectors?

Through bites from infected insects, like ticks or mosquitoes

How can diseases spread through food and water?

By consuming contaminated food or water

Example of bacterial diseases

Salmonella, gonorrhoea, tuberculosis, meningitis, strep throat, cholera

What is tuberculosis?

Bacterial infection of the lungs

How is tuberculosis transmitted?

Inhalation of airborne droplets

What are the symptoms of tuberculosis?

Coughing, chest pain, weight loss, fever

How can tuberculosis be treated/prevented?

Antibiotics (e.g., Rifampicin), vaccination

What is cholera?

An infectious disease of the small intestine caused by bacteria.

How is cholera transmitted?

contaminated water or food

What are the symptoms of cholera?

Diarrhoea, vomiting, dehydration

How can cholera be treated?

Rehydration therapy, antibiotics, improve sanitation

What is gonorrhoea?

a sexually transmitted disease caused by bacteria

How is gonorrhoea transmitted?

sexual contact

What are the symptoms of gonorrhoea?

-Thick yellow or green discharge

-Pain when urinating

How can gonorrhoea be treated?

antibiotics

What is Salmonella?

A type of bacteria that causes food poisoning

How is Salmonella transmitted?

contaminated food and water

What are the symptoms of Salmonella?

Fever, stomach cramps, vomiting and diarrhoea

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.

What is strep throat?

a bacterial infection of the throat and tonsils

How is strep throat transmitted?

respiratory droplets

How can strep throat be treated?

Antibiotics such as penicillin

Examples of fungal diseases

Athlete's foot, ringworm, and candidiasis

What is athlete's foot?

fungal infection

How is athlete's foot transmitted?

Direct contact with infected skin or contaminated surfaces

What are the symptoms of athlete's foot?

Itchy, cracked skin between toes

How can athlete's foot be treated/prevented?

Antifungal creams, good foot hygiene

Examples of viral diseases

Influenza (flu), common cold, chickenpox, measles, HIV/AIDS, COVID-19

What is influenza?

flu

How is influenza transmitted?

via droplets generated when infected persons cough or sneeze

What are the symptoms of the flu?

pain, achy, fever, runny nose, sore throat, fatigue, muscle aches

How can the flu be treated/prevented?

Antiviral medication, vaccination

What is the common cold?

viral infection of the upper respiratory tract

How is the common cold transmitted?

Via airborne droplets, sneezing, secreting snot etc.

What are the symptoms of the common cold?

nasal stuffiness, scratchy throat, headache, sneezing, and coughing

What is COVID-19?

An infectious disease caused by the newly discovered coronavirus SARS-Cov-2

How is COVID-19 transmitted?

Through respiratory droplets.

What are the symptoms of COVID-19?

fever, cough, difficulty breathing, loss of taste/smell

How can COVID-19 be prevented?

Vaccination, quarantine, mask-wearing

What is chicken pox?

contagious viral infection

How is chicken pox transmitted?

via direct contact with the blisters, saliva or mucus of an infected person. The virus can also be transmitted through the air by coughing and sneezing

What are the symptoms of chicken pox?

fever and rash

What is measles?

infection of the respiratory system

How is measles transmitted?

respiratory droplets from coughing/sneezing

What are the symptoms of measles?

Fever and a red skin rash

How can measles be prevented?

vaccination

What is HIV?

HIV is a virus that affects the immune system and eventually causes AIDS

How is HIV transmitted?

- bodily fluids

- sexual contact

- blood

- breast milk

What are the symptoms of HIV?

Fever, weight loss, night sweats, diarrhoea, fatigue

How can HIV be treated/prevented?

Antiretroviral therapy (ART), prevention through safe sex

What is AIDS?

AIDS is the end stage of the HIV infection. At this point, the virus has attacked and weakened a person's immune system. People are classed as suffering with AIDS when their white blood cells drop below a certain level.

How is AIDS transmitted?

sexual contact, transfusion of infected blood, contaminated needles and syringes

How can AIDS be treated/prevented?

Antiretroviral therapy (ART), prevention through safe sex

Examples of protistic diseases

malaria and giardiasis

What is malaria?

Malaria is a disease caused by protist pathogens. The disease is carried from host to host by mosquitoes, and the protists enter the human bloodstream when they feed.

How is malaria transmitted?

Vectors (mosquito bites)

What are the symptoms of malaria?

Chills, sweating, fatigue, recurrent fevers and can lead to death

How can malaria be treated?

antimalarial drugs

How can malaria be prevented?

- Sleeping under mosquito nets

- Using insect repellents

- Killing mosquitoes using insecticide

- Eliminate standing water to destroy breeding grounds

How is the spread of disease is prevented?

- vaccination

- good hygiene

- quarantine

- disinfectants

- antiseptics

- keeping away from uncooked food or contaminated water

- Insect control

- insecticides

- Antibiotics and antivirals

What are vaccinations?

Weak or dead pathogens that are injected into your body

How do vaccinations prevent the spread of disease?

Vaccines help the body's immune system recognise and fight off specific pathogens before infection occurs.

How does good hygiene prevent the spread of disease?

Washing hands regularly with soap and water, using tissues when coughing or sneezing, and cleaning surfaces reduce pathogen transmission.

What are antibiotics?

Drugs that kill or prevent the growth of bacteria without killing healthy body cells

What are antivirals?

A Drug that interferes with the viral life cycle, preventing release of new viral particles, some antivirals alter cells DNA so that the virus cannot use the cell to multiply.

How does quarantine and isolation prevent the spread of disease?

Infected individuals should be isolated to prevent the spread of contagious diseases.

What are disinfectants?

chemicals that kill or inhibit harmful microorganisms on non-living surfaces

What are antiseptics?

substances that kill or slow the growth of microorganisms (like bacteria) on living surfaces (like skin) to prevent infection

What are insecticides?

chemicals designed to kill or repel insects

How does insect control prevent the spread of disease?

Using insect repellent, nets, and eliminating breeding grounds for vectors like mosquitoes can prevent diseases like malaria.

What are bacteria?

simple, single-celled prokaryotic organisms

How do bacteria reproduce?

asexually through binary fission

How do bacteria enter the body?

- inhalation

- ingestion

- open wounds

- direct contact

What conditions are best for bacterial growth?

a warm, moist environment, like the respiratory tract, intestines or bloodstream

How do bacteria cause harm?

Bacteria can produce toxins that damage tissues, leading to symptoms like fever, inflammation, and pain.

How do viruses enter the body?

Inhalation

Body fluid exchange

Ingestion of contaminated food/water

Insect bites

How do viruses cause harm?

Viruses invade host cells and take over the cell's machinery to reproduce. This causes the host cell to burst or malfunction, leading to tissue damage and symptoms like fatigue and swelling.

Why do viruses take over host cells?

because they can't reproduce outside of host cells, because they have organelles. (However, they have DNA & RNA)

What are viruses?

tiny, non-living particles made of genetic material (DNA/RNA) that can't reproduce independently

What are fungi?

eukaryotic organisms that are not plants or animals, have cells with a nucleus and cell wall, and get food by absorbing nutrients from dead or living matter

What are parasites?

an organism that lives on or inside another organism (the host) and benefits by taking nutrients or resources from the host, causing harm to the host in the process, without giving anything beneficial in return

How do fungi enter the body?

Through the skin, mucous membranes, respiratory tract

How do fungi cause harm?

- invade tissues with thread-like hyphae

- release spores that spread infections (like athlete's foot or rose black spot)

- consume host nutrients

- produce harmful toxins, triggering severe immune responses

Are viruses living or non-living?

They are nonliving because they cannot make food or waste, nor adapt to the environment.

What are protists?

Single-celled eukaryotic organisms

What are vectors?

animals that carry pathogens from one host to another without getting the disease

How do protists enter the body?

via a vector (such as an infected mosquito biting a person) and injecting the protist into the bloodstream, or through contaminated water

How do protists cause harm?

They can invade tissues and damage cells, often causing conditions like malaria, where red blood cells are destroyed.

Examples of vectors?

mosquitos, ticks, fleas

How long does it take for bacteria to reproduce?

every 20 minutes in the right conditions

Formula for number of bacterial divisions

2ⁿ

where n = number of divisions

Formula for bacterial growth

Final population = initial population × 2ⁿ

where n = number of divisions

What factors affect bacterial growth?

Temperature, oxygen concentration, pH, external solute concentration, pressure