This cheat sheet covers common diseases and conditions that students may hear about in health class, medical science, or everyday life. It helps organize the differences between infectious diseases, chronic diseases, injuries, immune responses, and emergencies. Students need this reference to connect symptoms, causes, prevention, and basic health measurements in a clear way.
It is meant for learning and review, not for diagnosing or treating illness.
Key Facts
- Infectious diseases are caused by pathogens such as bacteria, viruses, fungi, or parasites and can spread through contact, droplets, blood, food, water, or vectors.
- Chronic diseases such as asthma, diabetes, heart disease, and arthritis usually last 3 months or longer and often require long-term management.
- Fever is commonly defined as a body temperature of 100.4°F or 38°C or higher, and it often signals infection or inflammation.
- Body mass index is calculated as BMI = weight in kilograms ÷ height in meters squared, and it is one screening tool for weight-related health risk.
- Heart rate is measured in beats per minute, and a typical resting adult range is about 60 to 100 beats per minute, though athletes may be lower.
- Blood pressure is written as systolic/diastolic in mmHg, and values around 120/80 mmHg are often considered a common reference point for adults.
- Type 1 diabetes involves little or no insulin production, while type 2 diabetes involves insulin resistance and often develops with genetic and lifestyle risk factors.
- Prevention strategies include vaccination, handwashing, safe food handling, exercise, balanced nutrition, sleep, avoiding tobacco, and following medical advice.
Vocabulary
- Pathogen
- A pathogen is a microorganism or agent, such as a virus or bacterium, that can cause disease.
- Symptom
- A symptom is a change a patient feels or reports, such as pain, nausea, fatigue, or dizziness.
- Sign
- A sign is an observable or measurable clue of illness, such as fever, rash, swelling, or high blood pressure.
- Risk Factor
- A risk factor is anything that increases the chance of developing a disease or condition.
- Inflammation
- Inflammation is the body's protective response to injury or infection, often causing redness, heat, swelling, and pain.
- Chronic Disease
- A chronic disease is a long-lasting condition that usually develops slowly and requires ongoing care or lifestyle management.
Common Mistakes to Avoid
- Confusing signs and symptoms is a common mistake because symptoms are felt by the patient, while signs can be observed or measured by others.
- Assuming antibiotics treat viral infections is wrong because antibiotics target bacteria, not viruses such as the common cold or flu.
- Ignoring risk factors because a person feels healthy is unsafe because many conditions, including high blood pressure and type 2 diabetes, may develop silently.
- Using BMI as a complete diagnosis is wrong because BMI is only a screening tool and does not directly measure muscle mass, body fat distribution, or overall health.
- Thinking all chest pain has the same cause is dangerous because chest pain can come from muscles, lungs, digestion, anxiety, or the heart and may need urgent evaluation.
Practice Questions
- 1 A student has a temperature of 101.3°F. Based on the common fever threshold of 100.4°F, does this count as a fever?
- 2 Calculate the BMI for a person who weighs 72 kg and is 1.80 m tall using BMI = weight in kilograms ÷ height in meters squared.
- 3 A patient's blood pressure is recorded as 145/92 mmHg. Which number is systolic, which number is diastolic, and how does it compare with the common reference point of 120/80 mmHg?
- 4 Explain why prevention methods such as vaccination, handwashing, exercise, and avoiding tobacco can reduce disease risk even when they do not guarantee perfect protection.
Understanding Common Diseases & Conditions
Disease categories overlap more than charts can show. An infection can be short lived, yet it may trigger inflammation that continues after the pathogen is gone. Inflammation is part of the immune response.
Blood flow increases, immune cells move into tissue, and chemicals signal the body to repair damage. This can cause redness, warmth, swelling, pain, fatigue, or fever. These signs do not identify one specific illness.
A sore throat may come from a virus, bacteria, allergies, irritation, or acid reflux. Learning to separate a symptom from its cause is important.
Symptoms are what a person feels or observes. Signs are measurable findings, such as a temperature reading or a rash seen by a clinician.
Chronic conditions often involve body systems that must keep a narrow balance. In asthma, airways can become inflamed and narrowed, making it harder to move air. In diabetes, the body has trouble keeping blood glucose within a healthy range because insulin is missing, ineffective, or both.
Over time, high blood glucose can harm blood vessels and nerves. This explains why long term conditions are managed consistently rather than only when symptoms become severe.
Medicines, activity, food choices, sleep, stress management, and follow up care can each affect that balance. Genetics can raise a person’s risk, but risk is not a prediction of what will happen to one individual.
Vital signs are useful because they show how the body is functioning at one moment. A number only makes sense with context. Heart rate rises during exercise, fear, pain, dehydration, fever, and some illnesses.
Blood pressure can change with posture, activity, stress, caffeine, and the size of the cuff used for measurement. A reading taken after sitting quietly is more useful for comparison than one taken right after climbing stairs. Health workers look for patterns across repeated measurements instead of drawing conclusions from a single unusual value.
Students should learn what each measurement represents. The upper blood pressure number reflects pressure as the heart contracts.
The lower number reflects pressure while the heart relaxes between beats. Units and measurement technique matter because small errors can produce misleading results.
Prevention works by interrupting a chain of events. Handwashing reduces the number of germs that can reach the mouth, nose, eyes, food, or other people. Vaccines train immune defenses before exposure, which can lower the chance of severe disease.
Safe food preparation limits contamination and stops microbes from multiplying. For chronic disease, prevention often means reducing risks over many years. Regular movement supports the heart, muscles, mood, and blood sugar control.
Adequate sleep affects immune function and hormone balance. Urgent warning signs deserve immediate adult or medical help. These include trouble breathing, chest pressure, fainting, sudden weakness on one side, confusion, uncontrolled bleeding, seizures, or signs of a severe allergic reaction.