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I've extracted all the content from the PDF. Here's a thorough explanation of everything covered in this Virology in 1 Page summary sheet:
Virology - Complete Explanation
This sheet organizes all major viruses by their genome type (DNA vs RNA), structure (enveloped vs naked), and clinical relevance. Here's each section broken down:
1. Basic Classification Framework
Viruses are first divided by genome:
- DNA viruses: ds (double-stranded) or ss (single-stranded)
- RNA viruses: mostly ss (single-stranded), positive or negative sense
- Non-enveloped (naked) viruses are sensitive to ether, alcohol, bile salts, and heat - important because it affects disinfection and fecal-oral transmission survival
- Enveloped viruses are more fragile
2. RNA Viruses
Reoviridae (ds RNA, Non-enveloped, Segmented - 11 segments)
- Rotavirus: Most common cause of viral gastroenteritis in children <2 years
- Diagnosis: Antigen ELISA
- Vaccine: Live oral - Rotateq, Rotarix
- Colorado tick fever: Arbo virus in this family
Picornavirus (ss RNA, Naked, Non-enveloped)
Divided into two major subgroups by route of transmission:
Enterovirus (Feco-oral route):
| Virus | Disease |
|---|---|
| HAV (Hepatitis A) | Acute hepatitis, IgM antibody ELISA for diagnosis |
| Poliovirus | Poliomyelitis - 99% asymptomatic, 1% meningitis, 0.1% acute flaccid paralysis (Iceberg phenomenon) |
| ECHO virus | "Enteric cytopathic human orphan" |
| Coxsackie A-16 / Enterovirus 71 | Hand-Foot-Mouth Disease (HFMD) with rashes |
| Coxsackie A-24 / Enterovirus 70 | Acute hemorrhagic conjunctivitis |
| Coxsackie B-3 | Myocarditis + Bornholm's disease |
| Enterovirus 72 | Hepatitis A |
- Polio vaccine: OPV (Live/Sabin strain) vs fIPV (Killed/Salk strain)
- Diagnosis: PCR (stool specimen)
Rhinovirus (Inhalational route):
- Binds to ICAM receptors on respiratory mucosa
- Causes the common cold
Orthomyxovirus (Segmented RNA - 8 segments, Enveloped)
- Influenza A and B (most common)
- Key surface proteins:
- Hemagglutinin (HA) - mediates viral entry
- Neuraminidase (NA) - mediates viral exit
- Antigenic Shift = Genetic reassortment → causes Pandemics (e.g., H1N1)
- Antigenic Drift = Point mutation → causes Epidemics
- H1N1 is a subtype of Influenza A
- Treatment:
- NA inhibitors: Oseltamivir (oral), Zanamivir (nasal), Peramivir
- M2 inhibitors: Amantadine, Rimantadine
- Vaccine: Live (inhalational) or Killed (IM - advised)
- Lab: Nasopharyngeal swab → Hemagglutination Inhibition test
- Bioterrorism: Category C
Paramyxovirus (Enveloped)
Includes: Parainfluenza, Nipah, Measles (Rubeola), Mumps, RSV, hMPV
Measles (Rubeola):
- Primary: Fever + 3 Cs = Coryza, Cough, Conjunctivitis + Rash
- Koplik spots - white spots opposite molar teeth (pathognomonic)
- Complication: SSPE (Subacute Sclerosing Panencephalitis) on reactivation
- Cytopathic effect: Warthin-Finkeldey giant cells (syncytium formation)
- Vaccine: Live - Edmonston-Zagreb strain
Mumps:
- Bilateral parotitis + Unilateral orchitis
- Lab: Detect antibody
- Vaccine: Live
RSV / hMPV:
- RSV: LRTI most common in children; URTI most common in adults
- Treatment: Ribavirin
- Prophylaxis: Palivizumab
Nipah:
- Vector: Fruit bat
- Viral encephalitis
- Bioterrorism: Category C
- Rx: Supportive
Calicivirus (Non-enveloped)
- Norovirus, Sapovirus - Viral gastroenteritis
- Also Astrovirus in this category
Arenavirus
- Lassa fever virus - Viral Hemorrhagic Fever (VHF)
Bunyavirus (Arbo virus)
- Hantavirus: VHF + Pneumonia
- CCHF (Crimean-Congo Hemorrhagic Fever): Vector = Ixodid tick; Lab: PCR; Treatment: Supportive
Rhabdovirus
- Rabies virus: 100% fatal; bullet-shaped
- Vector: Animal bite - Dog (India), Bat (World)
- Lab: Negri bodies on autopsy; PCR from saliva > CSF; Ag by DFA from skin (nape of neck) > cornea
- Treatment: Immunoglobulins + Killed vaccine (deltoid)
- Also includes: Chandipura virus, Vesicular stomatitis virus
Filovirus
- Ebola, Marburg: VHF + Septic shock
- Bioterrorism: Category A
- Vaccine: Zaire vaccine (Ebola)
Retrovirus (Enveloped, Biggest/Largest genome, 2 copies of ssRNA)
HIV:
| Stage | Features |
|---|---|
| Stage 1 | Asymptomatic + Generalised lymphadenopathy |
| Stage 2 | Oral aphthous ulcers, Herpes zoster, Candidiasis |
| Stage 3 | White patches in oral cavity (Oral Hairy Leukoplakia - EBV), Pulmonary TB, fever, diarrhoea >1 month |
| Stage 4 (AIDS) | Oesophageal candidiasis, Wasting syndrome, Extrapulmonary TB, Kaposi's sarcoma (most common cancer), other OIs |
- Mode of transmission: Blood, body fluids
- Screening: ELISA; Confirmatory: Western Blot
- Treatment: TLD (Tenofovir + Lamivudine + Dolutegravir) - lifelong
HTLV (Human T-cell Lymphotropic Virus):
- Tax gene
- Causes: ATLL (Adult T-cell Leukemia/Lymphoma), Tropical spastic paraparesis
- Microscopy: Clover leaf cells
Coronavirus (Enveloped)
- Petal-like structures (spike proteins)
- Receptors: Spike/flower petal
- Atypical pneumonia
- Antigenic shift = Pandemic; Antigenic drift = Epidemic
- Radiology: Multifocal ground glass opacities
- Lab: rRT-PCR
- Vaccine: Covishield (Subunit/s.Ag), Covaxin (Killed)
- Bioterrorism: Category C
Flavivirus (Arbo viruses)
| Virus | Key Feature |
|---|---|
| Japanese Encephalitis (JE) | Vector: Culex mosquito; Reservoir: Ardeid birds; Amplifier: Pig; Vaccine: Live SA-14-14-2 / Killed Kolar strain |
| West Nile | Viral encephalitis |
| KFD (Kyasanur Forest Disease) | Vector: Ixodid tick; Reservoir/Amplifier: Rat/squirrel/Monkey; aka monkey fever |
| Dengue | Vector: Aedes aegypti/albopictus; Dengue hemorrhagic fever + Dengue shock syndrome; Decreased platelets + Increased hematocrit (plasma loss); Lab: <5 days PCR/NS1 Ag; ≥5 days Ab detection |
| Yellow Fever (YF) | Midzonal necrosis of liver; Ballooning of cells; Vaccine: 17-D strain (Live); Torres bodies |
| Zika | Microcephaly + Subcortical calcifications |
| HCV | Lab: IgM HCV (1st test), PCR (confirmatory); Treatment: Sofosbuvir + Velpatasvir |
Togavirus (Arbo virus)
- Chikungunya: Fever + Migratory polyarthritis/arthralgia + Chick sign (pigmentation over nose); Vector: Aedes
- EEE, WEE: Eastern/Western Equine Encephalitis
Rubella (Matona/Togavirus)
- Congenital Rubella Syndrome Triad:
- Eye: Cataract
- Ear: Sensorineural hearing loss
- Heart: Patent Ductus Arteriosus (PDA)
- Also: "Blueberry muffin" rash, Forchheimer spots (bleeding spots on uvula/hard palate)
- Vaccine: Live RA 27/3 strain
- Lab: PCR
HEV (Hepatitis E Virus - Calicivirus family)
- Feco-oral transmission
- High mortality in pregnancy
- Lab: IgM antibody ELISA
HDV (Delta Virus - Rhabdovirus-like, smallest genome)
- Requires HBV co-infection
- Route: Parenteral, sexual, vertical
- Coinfection (HBV + HDV together): IgM HDV + IgM HBV
- Superinfection (HDV infects someone with chronic HBV): IgM HDV + IgG HBV
3. DNA Viruses
Parvovirus (ssDNA, Naked, Smallest virus)
- Parvovirus B19 - positive sense, non-enveloped
- Presentations:
- Children: Slapped cheek appearance (erythema infectiosum / Fifth disease)
- Adults: Arthralgia
- Sickle cell anemia: Aplastic crisis
- Immunocompromised: Pure red cell aplasia
- Congenital: Non-immune fetal hydrops
Papillomaviridae (HPV - dsDNA, Circular, Naked)
Cutaneous involvement:
- Low risk (1, 2, 3): common warts
- High risk (5, 8): Epidermodysplasia Verruciformis (Tree Man Syndrome)
Mucosal involvement:
- Low risk (6, 11): Anogenital warts (Condyloma acuminata)
- High risk (16, 18, 31, 33, 45, 52, 58): Oropharyngeal + Urogenital cancers (cervical Ca, penile Ca)
HPV Proteins:
- E6: Inhibits p53 ("policeman of the genome") - causes cancer
- E7: Inhibits Rb protein ("governor of the genome") - causes cancer
- L1: Capsid protein - used to make HPV vaccines
- E2: Controller; tries to stop cancer progression
- E4, E5: Form Koilocytes (pathognomonic histology)
Vaccines:
- Bivalent (Cervarix): Types 16, 18
- Quadrivalent (Gardasil): Types 6, 11, 16, 18
- Nonavalent (Gardasil 9): 9 strains
Hepadnavirus (HBV - Partially dsDNA, Circular)
- Route: Parenteral, sexual, vertical
- Lab: HBsAg (+ve = active infection), HBeAg (+ve = high infectivity, -ve = low infectivity), Anti-HBc (IgM = acute, IgG = chronic)
- Vaccine: Subunit vaccine (HBsAg)
- Treatment: Tenofovir (>1 year)
- Leads to: Acute hepatitis → Chronic hepatitis → Hepatocellular carcinoma
Polyomavirus
- BK virus: Infection in post-renal transplant patients
- JC virus: Causes Progressive Multifocal Leukoencephalopathy (PML) - viral encephalitis; Lab: PCR
- SV40: Simian vacuolating virus-40 - Mesothelioma
- Merkel Cell Virus: Merkel cell carcinoma (neuroendocrine skin tumor)
Adenovirus (dsDNA, Naked - "spaceship" shaped)
- Atypical pneumonia
- Viral gastroenteritis: Adenovirus 40, 41
- Receptors: Long antenna-like
- Cytopathic effect: Granular clumping + "Bunch of grapes"
- Diagnosis: PCR
- Cowdry Type B inclusion bodies
Poxvirus (dsDNA, Enveloped, Largest DNA virus - brick/box with dumbbell shaped core)
| Virus | Disease |
|---|---|
| Variola | Smallpox - eradicated in 1980; Bioterrorism Category A |
| Monkeypox | Severity: severe (septic shock) - all papules umbilicated |
| Vaccinia | Cowpox |
| Molluscum contagiosum | Umbilicated papules; HP (Henderson-Patterson) bodies |
- Clinical: Macules → Umbilicated papules → Pustules
- Lab: PCR
- Treatment: Brincidofovir, Tecovirimat
- Vaccine: Live smallpox vaccine
Herpesviridae (dsDNA, Enveloped)
All herpes viruses have both intranuclear and intracytoplasmic inclusion bodies
| HHV | Common Name | Key Disease | Notes |
|---|---|---|---|
| HHV-1 (HSV-1) | Herpes Simplex 1 | Lesions above the waist, sporadic temporal lobe encephalitis, herpetic whitlow, Mollaret's meningitis | Latency in trigeminal ganglia; Tzanck smear = multinucleate giant cells; Rx: Acyclovir; Cowdry Type A (Lipschütz bodies) |
| HHV-2 (HSV-2) | Herpes Simplex 2 | Lesions below the waist, genital herpes, neonatal herpes | Latency in sacral ganglia; Rx: Acyclovir |
| HHV-3 (VZV) | Varicella Zoster | Primary: Chickenpox ("dew drop on rose petal" vesicles, entire body); Reactivation: Herpes Zoster/Shingles | Complications: Post-herpetic neuralgia, Zoster Ophthalmicus, Ramsay Hunt Syndrome; Vaccine: Live chickenpox vaccine |
| HHV-4 (EBV) | Epstein-Barr Virus | Infectious Mononucleosis ("Kissing Disease"), Gastric & nasopharyngeal cancer, Burkitt's & Hodgkin's lymphoma, Oral Hairy Leukoplakia | Lab: PCR; Treatment: Acyclovir (OHL), Rituximab |
| HHV-5 (CMV) | Cytomegalovirus | "Owl's Eye" appearance (intranuclear inclusions); Congenital CMV (worst in 1st trimester): SNHL, Chorioretinitis, Microcephaly, Periventricular calcification, Cicatrization | Immunocompromised: CMV Chorioretinitis (retinitis); Rx: Ganciclovir (intravitreal for retinitis), Foscarnet, Cidofovir |
| HHV-6 | Roseola | Viral encephalitis; Nagayama spots in oral cavity | Roseola infantum |
| HHV-7 | Roseola | Roseola | - |
| HHV-8 | KSHV | Kaposi's sarcoma (reddish, elevated, vascular tumor - most common in HIV) | - |
4. Inclusions & Cytopathic Effects Summary
| Inclusion | Virus |
|---|---|
| Negri bodies (intracytoplasmic) | Rabies |
| Cowdry Type A / Lipschütz bodies (intranuclear) | Herpes (HSV) |
| Torres bodies (intracytoplasmic) | Yellow Fever |
| Cowdry Type B (intranuclear) | Adenovirus, Poliovirus |
| Owl's Eye (both) | CMV |
| Warthin-Finkeldey giant cells | Measles |
| HP (Henderson-Patterson) bodies | Molluscum Contagiosum |
| Koilocytes | HPV |
5. Viral Cultivation Methods
| Method | Used For |
|---|---|
| Animal inoculation - Suckling mice | Coxsackie virus |
| Egg - Chorioallantoic membrane | Vaccinia, Variola, HSV-1, HSV-2 |
| Egg - Allantoic cavity | Primary isolation of Influenza |
| Egg - Amniotic cavity | Primary isolation of Influenza (earlier passages) |
| Egg - Yolk sac | Arboviruses, Chlamydia, Rickettsia |
| Cell lines - Primary (5-10 divisions) | - |
| Cell lines - Secondary (10-50 divisions) | - |
| Cell lines - Continuous (unlimited) | Yellow fever vaccine, Influenza vaccine, Rabies vaccine |
| Bacteriophage (tadpole-shaped, DNA virus) | Transduction |
6. Bioterrorism Categories
| Category | Viruses |
|---|---|
| Category A (most dangerous) | Smallpox (Variola), Ebola/Marburg (Filovirus) |
| Category C | Influenza, Nipah, Coronavirus |
7. Cancer-Causing Viruses (Oncogenic)
| Virus | Cancer |
|---|---|
| HPV (16, 18) | Cervical, penile, oropharyngeal |
| HBV, HCV, HDV | Hepatocellular carcinoma |
| EBV (HHV-4) | Burkitt's lymphoma, Hodgkin's, nasopharyngeal/gastric Ca |
| HHV-8 | Kaposi's sarcoma |
| HTLV | Adult T-cell leukemia/lymphoma (ATLL) |
| Merkel cell virus | Merkel cell carcinoma |
| SV40 | Mesothelioma |
8. TORCH Infections
- Toxoplasma, Other (including Parvovirus B19, VZV, HBV), Rubella, CMV, Herpes
- These viruses cause significant congenital disease when acquired during pregnancy
Key Mnemonics from the Sheet
- TLD = Tenofovir + Lamivudine + Dolutegravir (HIV treatment)
- 3 Cs of Measles = Coryza, Cough, Conjunctivitis
- Rubella Triad = Cataract + SNHL + PDA
- Polio Iceberg = 99% asymptomatic : 1% meningitis : 0.1% AFP
- HA = Entry, NA = Exit (Influenza)
- E6 kills p53, E7 kills Rb (HPV oncoproteins)
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