week 9 micro

genome

DNA or RNA

capsid

protein coat

envolope

lipid membrane in some viruses

innate immunity

phagocytes, NK cells

adaptive immunity

B and T cells

active naturally acquired

own adaptive response. Hep A infection

active medically provded

vaccine

passive naturally aquired

received antibodies, through placenta

passive medically provided

rabies.

measles

• Pathogen: Measles virus (enveloped RNA virus)

• Reservoir: Humans

• Transmission: Airborne. Virus can remain in the air for up to 2

hours after the person leaves.

• Mechanism: Respiratory entry → viral replication → spread through

lymphatic tissues and blood → systemic infection

• Infectious period: Usually 4 days before through 4 days after rash

onset

Rubella

• Pathogen: Rubella virus (enveloped RNA virus).

• Reservoir: Humans.

• Transmission: Respiratory droplets and transmission across the

placenta.

• Mechanism: Respiratory entry → replication in the nasopharynx

and lymph nodes → bloodstream spread → systemic infection.

• Infectious period: Approximately 7 days before through 7 days

after rash onset

chickenpox and shingles

• Pathogen: Varicella-zoster virus (VZV), an enveloped DNA virus.

• Reservoir: Humans

• Transmission: Contact with blister fluid or inhalation of infectious

virus particles.

• Mechanism: Primary VZV infection → chickenpox → latency in

sensory nerve ganglia → possible later reactivation → shingles.

• Infectious period:

• Chickenpox: 1-2 days before rash onset until all lesions crust.

• Shingles: From blister appearance until all lesions are dry and crusted

Mpox

• Pathogen: Monkeypox virus (MPXV), an enveloped DNA virus.

• Reservoir/source: Natural reservoir is uncertain. Infected people

and animals can transmit the virus.

• Transmission: Close physical contact, including sexual contact.

Contaminated materials and animal exposure.

• Mechanism: Entry through skin/mucosa → replication → lesions

and sometimes systemic illness.

• Infectious period: May begin before symptoms and continues

until all lesions heal, scabs separate, and healthy new skin forms.

measles precautions

standard plus airborne

influenza precautions

standard plus droplet

chickenpox percautions

standard plus airborne plus contact

mumps precautions

standard plus droplet

pulmonary Tb precautions

standard plus airborne

seasonal influenza

• Pathogen: Influenza A & B viruses (enveloped RNA viruses).

• Reservoir: Humans

• Transmission: Respiratory droplets and smaller particles.

• Mechanism: Respiratory entry → replication in respiratory

epithelial cells → cell injury and inflammation.

• Infectious period: About 1 day before through 5-7 days after

symptom onset.

Covid 19

• Pathogen: SARS-CoV-2 (an enveloped RNA coronavirus).

• Reservoir: Humans

• Transmission: Inhalation of infectious respiratory particles.

• Mechanism: Viral replication causes respiratory cell injury and

inflammation. Severe lung involvement can impair gas exchange

and cause hypoxemia.

• Infectious period: About 1-2 days before through 8-10 days after

symptom onset.

RSV infections

• Pathogen: Respiratory syncytial virus (an enveloped RNA virus).

• Reservoir: Humans

• Transmission: Respiratory droplets, direct contact, and

contaminated hands or surfaces.

• Mechanism: Airway infection → inflammation. In infants, swelling,

mucus, and cell debris can obstruct small airways.

• Infectious period: Usually contagious 3-8 days; may begin 1-2

days before symptoms

infectious mononucleosis

• Pathogen: Most often Epstein-Barr virus (EBV), an enveloped DNA

virus

• Reservoir: Humans

• Transmission: Mainly saliva (e.g., kissing, sharing drinks/utensils)

• Mechanism: Oropharyngeal entry → infection of B lymphocytes →

immune activation and lymphoid tissue enlargement. EBV

remains latent after infection and can reactivate.

• Infectious period: May spread before symptoms; salivary

shedding can persist for months and recur intermittently.

mumps

• Pathogen: Mumps virus, an enveloped RNA virus

• Reservoir: Humans

• Transmission: Respiratory droplets and direct contact with

infected saliva

• Mechanism: Replication in the upper respiratory tract and nearby

lymph nodes → bloodstream spread → inflammation of salivary

glands and sometimes other organs

• Infectious period: Usually 2 days before through 5 days after

salivary gland swelling begins.

viral gastroenteritis

• Common Pathogens: Norovirus and rotavirus (both

nonenveloped RNA viruses)

• Transmission: Fecal-oral spread via contaminated hands, food,

water, or surfaces.

• Mechanism: Intestinal infection disrupts absorption and

secretion. Vomiting and diarrhea cause fluid and electrolyte

losses.

• Infectious period: Transmission is greatest during illness and

early recovery. Viral shedding can continue after symptoms

resolve.

HAV

Fecal-oral route, including

contaminated food/water and close contact. Acute infection, vaccine available

HBV

blood, sexual contact and perinatal exposure. acute or chronic infection

HCV

mainly blood exposure. often chronic

HDV

blood and other infectious body fluids. Requires HBV. prevented by preventing HBV

HEV

contaminated water or undercooked meat. acute, risk of severe disease during pregnancy

genital herpes

• Pathogen: HSV-1 or HSV-2, enveloped DNA viruses

• Reservoir: Humans

• Transmission: Direct skin or mucosal contact during sexual

activity, including oral-genital contact. Transmission to a newborn

can occur during birth.

• Mechanism: Local infection → lifelong latency in sensory nerve

ganglia → possible reactivation.

• Infectious period: Intermittent viral shedding can occur with or

without visible lesions.

genital HPV infection

• Pathogen: Human papillomaviruses (HPV), nonenveloped DNA

viruses

• Reservoir: Humans

• Transmission: Intimate skin-to-skin or mucosal contact.

• Course: Most infections become undetectable through immune

control, usually within 1-2 years.

• Wart-causing types: Types such as HPV 6 and 11 cause genital warts.

• Persistent high-risk types: Types such as HPV 16 and 18 can cause

precancer and cancer.

• Infectious period: Variable; HPV can spread without visible warts

and after warts resolve.

HIV infection

• Pathogen: HIV-1 and HIV-2, enveloped RNA retroviruses

• Reservoir: Humans

• Transmission: Sexual exposure, shared injection equipment, and

other blood exposures. Transmission can also occur during

pregnancy, birth, or breastfeeding.

• Mechanism: HIV infects CD4 T cells and establishes persistent

infection. Without treatment, progressive immune dysfunction

can lead to AIDS.

• Course: Acute infection may cause a nonspecific febrile illness.

Chronic infection may remain asymptomatic.

Undetectable HIV

equals untransmittable

PEP vs PrEP

PEP is urgent task

dengue

• Pathogen: Dengue viruses (DENV-1 to DENV-4), enveloped RNA

viruses

• Reservoir: Humans

• Transmission: Bite of an infected Aedes mosquito. Mosquitoes

acquire the virus when they bite a person with viremia.

• Mechanism: Viral replication produces viremia (virus in the

blood). Severe disease can involve plasma leakage from

increased vascular permeability, severe bleeding, or organ injury.

• Infectious period: To mosquitoes, from up to 2 days before

symptoms until up to 2 days after fever resolves.

rabies

• Pathogen: Rabies virus, an enveloped RNA virus

• Reservoir: Infected mammals, especially dogs, bats, wild

carnivores (species vary by region).

• Transmission: Infected saliva through bites, scratches, or contact

with broken skin or mucous membrane.

• Mechanism: Virus travels along peripheral nerves to the CNS,

causing progressive encephalitis.

• Course: Incubation usually lasts weeks to months. Neurologic

illness can involve agitation or progressive paralysis.

infants and young children concered with

RSV:Bronchitis and rotavirus: gastroenteritis

adolescents and young adults concerned with

EBV: Mono, HSV or herpes and HPV: sexually transmitted infections

older adults concerned with

flu Covid RSV: increased risk for severe respiratory illness

Pregnant patients concerned with

Influenza and COVID-19:

increased risk of severe maternal

illness.

fetus and newborns concerned with

Congenital CMV: hearing and

developmental problems. Rubella:

congenital rubella syndrome.

Parvovirus B19: fetal anemia.

immunocompromised patienst concerned with

CMV: retinitis or colitis. HSV and

VZV: severe or disseminated

infection.

Infants and young children vaccines

Rotavirus, polio, MMR, varicella, hepatitis A and B

adolescents and young adults vaccines

HPV and indicated catch-up

vaccines

older adults vaccines

Recombinant shingles vaccine and RSV vaccine

measles may include

Koplik spots

HSV 1 vs 2

1 more common with oral 2 more common with genital. But both still cause both

Chikengunya

prominent joint pain

cytomegalovirus causes

retinitis

tropism

compatible cells allow growth and replication