Pathogens and Infectious Diseases

MRSA: what is it and what causes it?

Methicillin-resistant Staphylococcus aureus; a strain of S. aureus resistant to several beta-lactam antibiotics.

MRSA: common signs and symptoms

Skin infections may be red, swollen, warm, painful, and pus-filled; invasive infections can cause fever and serious illness.

MRSA: how does it spread?

Direct skin contact or contact with contaminated items and surfaces.

MRSA: prevention

Hand hygiene, covering wounds, not sharing personal items, and cleaning shared equipment and surfaces.

Influenza: pathogen and symptoms

Influenza virus; fever, cough, sore throat, muscle aches, headache, chills, and fatigue.

Seasonal influenza: transmission

Mainly through infectious respiratory particles; hands and contaminated surfaces may also contribute.

H5N1 avian influenza: what is it?

A subtype of influenza A virus that primarily infects birds but can infect humans, usually after exposure to infected animals.

H5N1: possible symptoms and exposure

May cause eye redness or flu-like respiratory symptoms, sometimes severe disease; risk is associated with infected birds or other animals.

Tuberculosis (TB): pathogen

Mycobacterium tuberculosis, a bacterium that most often affects the lungs.

TB: signs and symptoms

Persistent cough, chest pain, coughing blood, fever, night sweats, weight loss, and fatigue.

TB: transmission

Airborne particles released by a person with infectious TB, especially with prolonged indoor exposure.

Histoplasmosis: cause and exposure

Histoplasma capsulatum, a fungus; people usually become infected by inhaling spores from contaminated soil, often disturbed by bird or bat droppings.

Histoplasmosis: signs and symptoms

May cause no symptoms or flu-like illness with fever, cough, chest pain, and fatigue; severe disease can affect the lungs or spread in the body.

Human herpes simplex virus (HSV): types

HSV-1 commonly causes oral herpes; HSV-2 commonly causes genital herpes, but either type can infect either site.

HSV: signs and symptoms

Painful blisters or ulcers around the mouth or genitals; infection can also be mild or symptom-free, with possible recurrences.

HSV: transmission

Direct contact with infected skin, sores, saliva, or genital secretions; transmission can occur even without visible sores.

Chickenpox and shingles: pathogen

Varicella-zoster virus (VZV); first infection causes chickenpox, and later reactivation can cause shingles.

Chickenpox: signs and symptoms

Itchy, fluid-filled blisters in crops, often with fever and fatigue.

Shingles: signs and symptoms

Pain, tingling, or burning followed by a blistering rash, usually in a band on one side of the body.

Chickenpox vs. shingles transmission

Chickenpox spreads readily through airborne particles and contact with blister fluid. Shingles can transmit VZV to a nonimmune person through rash fluid, causing chickenpox.

Measles: pathogen and symptoms

Measles virus; high fever, cough, runny nose, red watery eyes, Koplik spots in the mouth, then a spreading red rash.

Measles: transmission

Highly contagious airborne spread; virus can remain in the air after an infected person leaves.

Measles: prevention

MMR vaccination is the main prevention method; isolation and public-health guidance help limit outbreaks.

HIV: what cells does it affect?

HIV targets CD4 T helper cells, weakening immune defenses over time without effective treatment.

HIV: stages and symptoms

Early infection may cause flu-like symptoms; later infection may have few symptoms before immune damage becomes severe.

HIV: transmission

Certain sexual exposures, blood exposure such as shared injection equipment, and transmission during pregnancy, birth, or breastfeeding.

HIV: how is it not spread?

Not through casual contact, hugging, sharing food, or insect bites.