MBI Exam 3 Study Set

Virus

Acellular, non-living obligate intracellular parasite. Composed of nucleic acid (DNA or RNA) within a protein capsid; some have an envelope.

Viral Structure

Genetic Material (DNA/RNA); Capsid (protein shell); Envelope (lipid layer with spikes, optional). Naked viruses lack an envelope.

Viral Replication Cycle

1. Adsorption (attachment). 2. Penetration (entry). 3. Uncoating (genome release). 4. Synthesis (viral component production). 5. Assembly (new virions). 6. Release (lysis or budding).

Viral Infections

Acute (short, rapid); Latent (dormant, reactivates); Persistent (continuous replication).

Oncogenic Viruses

Viruses that can cause uncontrolled cell growth leading to cancer (e.g., HPV, Hepatitis B).

Prion

Infectious misfolded protein (no DNA/RNA). Causes fatal transmissible spongiform encephalopathies (TSEs) like CJD, BSE, leading to spongy brain tissue.

Acne

Caused by Cutibacterium acnes; hair follicles clogged with oil/dead cells. Treated with benzoyl peroxide, antibiotics, isotretinoin.

Staphylococcus aureus

Causes abscesses, boils; can lead to sepsis/pneumonia. Includes MRSA/VRSA strains. Treated by draining lesions, antibiotics. Prevented by hygiene.

Scalded Skin Syndrome

Caused by S. aureus exfoliative toxin; outer epidermis peels. Affects infants/children. Treated with antibiotics; prevented by hygiene.

Cellulitis

Deep skin infection by S. aureus/S. pyogenes. Symptoms: redness, swelling, warmth, pain. Treated with antibiotics; severe cases may need surgery.

Necrotizing Fasciitis

Invasive S. pyogenes/S. aureus destroying connective tissue ('flesh-eating disease'). Requires immediate surgery and antibiotics. Prevented by wound care.

Gas Gangrene

Caused by Clostridium perfringens; produces exotoxins leading to tissue death and gas. Treatment: amputation, antibiotics, hyperbaric oxygen.

Chickenpox

Caused by Varicella-Zoster Virus (HHV-3). Transmitted by airborne droplets/contact. Symptoms: itchy rash, fever. Complications: encephalitis. Prevented by VAR/MMRV vaccine.

Shingles

Reactivation of latent HHV-3, causing painful, localized rash along nerves.

Measles

Fever, cough, Koplik's spots, red rash.

Measles Complications

Encephalitis, pneumonia.

Measles and Rubella Prevention

MMR vaccine.

Rubella

Mild rash/low fever; teratogenic to fetus (Congenital Rubella Syndrome).

Common Cold

Caused by rhinoviruses & coronaviruses (>200 types).

Common Cold Symptoms

Sneezing, sore throat, runny nose.

Common Cold Treatment

Symptom relief; prevented by handwashing.

Strep Throat

Caused by Streptococcus pyogenes.

Strep Throat Symptoms

Sore throat, fever, pus on tonsils.

Strep Throat Complications

Scarlet fever, rheumatic fever, glomerulonephritis.

Strep Throat Treatment

Antibiotics.

RSV

Affects infants, elderly, and immunocompromised.

RSV Complications

Causes pneumonia and bronchiolitis.

RSV Treatment

Supportive treatment; prevented by RSV vaccine (60+), maternal antibodies (infants).

Influenza (Flu)

RNA virus with H/N spikes; mutates rapidly (antigenic drift/shift).

Influenza Symptoms

Fever, body aches, cough, fatigue.

Influenza Complications

Secondary bacterial pneumonia.

Influenza Treatment

Antivirals (early), rest, fluids; prevented by annual flu vaccine.

Pertussis (Whooping Cough)

Caused by Bordetella pertussis.

Pertussis Symptoms

Toxins damage cilia, causing mucus buildup and severe coughing fits.

Pertussis Treatment

Supportive treatment; prevented by DTaP/Tdap vaccine.

COVID-19

Caused by coronavirus SARS-CoV-2.

COVID-19 Transmission

Transmitted by droplets/aerosols; binds to ACE2 receptors.

COVID-19 Symptoms

Fever, cough, fatigue, loss of smell/taste, diarrhea.

COVID-19 Severe Cases

Can lead to cytokine storm, ARDS, multi-organ failure.

COVID-19 Treatment

Antivirals (e.g., Paxlovid), steroids, oxygen.

COVID-19 Prevention

Vaccines, masks, hand hygiene.

Long COVID

Post-infection condition lasting weeks to months. Fatigue, chest pain, brain fog, cognitive decline.

Infectious Mononucleosis

Caused by Epstein-Barr Virus (HHV-4).

Infectious Mononucleosis Transmission

Transmitted via saliva ('kissing disease').

Infectious Mononucleosis Symptoms

Fatigue, sore throat, swollen lymph nodes, enlarged spleen.

Infectious Mononucleosis Complications

Splenic rupture; avoid contact sports.

Infectious Mononucleosis Treatment

Rest, fluids, OTC meds.

Tuberculosis (TB)

Caused by Mycobacterium tuberculosis.

Tuberculosis Transmission

Transmitted by airborne droplets; primarily infects lungs.

Latent TB

Dormant, non-contagious; Active TB is contagious & symptomatic.

Tuberculosis Symptoms

Chronic cough, fever, weight loss, night sweats.

Tuberculosis Treatment

Long-term antibiotics (e.g., isoniazid, rifampin).

Tuberculosis Prevention

Screening, isolation, BCG vaccine (global).

Skin Defenses

Keratinized epidermis forms a physical barrier.

Skin Defenses Mechanisms

Sebum and sweat have antimicrobial properties.

Normal Microbiota

Protects by competing with pathogens.

Respiratory Defenses

Mucus traps microbes; cilia move debris out.

Alveoli Function

Handles gas exchange; infections here can be life-threatening.

Cold, Dry Air Effect

Reduces mucosal defenses, increasing infection risk.