VIROLOGY

VIRUSES
▪ Ultramicroscopic agents: 20-400 nm in diameter; “Filterable” agents
▪ Acellular
▪ Genetic material: Either DNA or RNA (Never both)
▪ Obligate intracellular agents
▪ Tissue-specific
▪ Host-specific
Taxonomy
▪ International Committee on Taxonomy of Viruses
▪ Taxonomic levels
o Order -virales E.g. Mononegavirales
o Family -viridae E.g. Paramyxoviridae
o Subfamily -virinae E.g. Paramyxovirinae
o Genus -virus E.g. Morbillivirus
o Species virus E.g. Measles virus
Viral Structure
Core
• Viral nucleic acidgenome
• Characteristics:
o Nature of nucleic acid: Either DNA or RNA
o Strandedness: Single-stranded/ Double-stranded
o Polarity/ Sense:
▪ Positive sense/ Positive strand/ Sense
▪ Negative sense/ Negative strand/ Antisense
a. (+)ssRNA c. (+) ssDNA e. dsDNA
b. (-)ssRNA d. dsRNA
o Shape:
▪ RNA: Continuous/ Segmented
▪ DNA: Linear/ Circular
Coat/ Capsid
• Protein shell of the virus surrounding the core
• Made up of repeating units called capsomeres
• Symmetry
o Helical
▪ Rod-shaped viruses
▪ Capsomeres arranged in a hollow coil
o Icosahedral
▪ Polyhedral/ Cubic; Rotational symmetry
▪ 12 apices/ corners; 25 triangular sides
o Complex
▪ Parts
• Head : Contains the nucleic acid
• Tail : Contractile/ hollow tube with a proximal sheath to the head
and a base plate distal to the head
• Tail fibers :Emanates from the base plate of the tail; recognize
and attaches to the host cells
▪ Bacteriophages, Pox viruses
*** All viruses are equipped with a nucleic acid core and the capsid coat
*** Nucleic acid core + Capsid → Nucleocapsid
Envelope
• Made up of lipids (derived from the infected host cell) and glycoproteins (Carbohydrate
moiety is derived from the host while the protein moiety is synthesized by the virus)
• (+): Enveloped viruses; (-) Naked viruses
o Enveloped viruses are more susceptible to effects of heat, detergents, solvents,
and alcohols

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 1

 Virion
• Complete virus particle; Infective virus

**Viroid
• Unencapsidated, small circular ssRNA molecules that replicate autonomously

IMPORTANT!!!
The next three pages are PIVOTAL to basic understanding of virology. PLEASE memorize.

Viral Classification (according to structure)

RNA VIRUSES DNA VIRUSES

Orthomyxoviridae Parvoviridae
Paramyxoviridae Papovaviridae
Rhabdoviridae Adenoviridae
Filoviridae Hepadnaviridae
Coronaviridae Herpesviridae
Bunyaviridae Poxviridae
Arenaviridae
Picornaviridae
Caliciviridae
Reoviridae
Togaviridae
Flaviviridae
Retroviridae

NOTES:
• Family Papovaviridae has been recently subdivided into two: Family Polyomaviridae and
Family Papillomaviridae

• For RNA viruses:

o All are single-stranded except Reoviridae
o All have continuous genomic architecture EXCEPT
• Orthomyxoviridae 8 segments
• Bunyaviridae 3 segments
• Arenaviridae 2 segments
• Reoviridae 10-12 segments
* Members of Family Retroviridae have 2 copies of their continuous
genome.
o All are characterized with a helical symmetry EXCEPT the following which are
characterized with an icosahedral symmetry
▪ Picornaviridae
▪ Caliciviridae
▪ Reoviridae
▪ Togaviridae
▪ Flaviviridae
▪ Retroviridae
o All are enveloped EXCEPT
▪ Picronaviridae
▪ Caliciviridae
▪ Reoviridae

• For DNA viruses:

o All are double-stranded EXCEPT Parvoviridae
o All have linear and continuous genomic architecture
▪ Except Papovaviridae (circular genome) and Hepadnaviridae (gapped
and circular genome)

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 2

 o All are characterized with an icosahedral symmetry EXCEPT Poxviridae which
has a complex symmetry
o All are naked EXCEPT
▪ Hepadnaviridae
▪ Herpesviridae
▪ Poxviridae
Baltimore Classification
• Classifies organisms based on mechanisms of mRNA production
Group I dsDNA
Papovaviridae, Adenoviridae, Herpesviridae, Poxviridae
Group II (+) ssDNA
Parvoviridae
Group III dsRNA
Reoviridae
Group IV (+)ssRNA
Coronaviridae, Picornaviridae, Caliciviridae, Togaviridae, Flaviviridae
Group V (-)ssRNA
Orthomyxoviridae, Paramyxoviridae, Rhabdoviridae, Filoviridae, Bunyaviridae,
Arenaviridae
Group VI (+) ssRNA; Utilizes reverse transcriptase
Retroviridae
Group VII dsDNA; Utilizes reverse transcriptase
Hepadnaviridae

Steps in Viral Replication Process

1. Adsorption / Attachment
▪ Specific interaction between receptor-binding proteins of the virus and the receptor
molecules in the host cell
o Receptor-binding proteins
▪ Naked viruses: Capsid proteins
▪ Enveloped viruses: Glycoproteins
▪ Highly specific
o Host-specificity
o Tissue-specificity

2. Penetration
▪ 3 ways
Viropexis
o Technique commonly employed by naked viruses
o Virus enters the host cell via endocytosis
o Virus is enclosed in an endosome and is released into the cytoplasm of the
infected host cell
Fusion
o Technique commonly employed by enveloped viruses
o Fusion proteins mediates the fusion of the lipids of the viral envelope and the
lipid of the host cell membrane → Release of nucleocapsid into the cytoplasm of
the infected host cell
Injection
o Used by few viruses only (e.g. Polioviruses)
o Viral genome directly passes through the cell membrane of the host cell into the
cytoplasm of the cell

3. Uncoating
▪ Separation of the nucleic acid from the capsid
▪ Suggested mechanisms:
Presence of lysosomal factors
Enzymes in the host cell cytoplasm
Virally-encoded enzymes

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 3

 4. Biosynthesis
▪ Replication of the viral genome → Transcription leading to formation of mRNA →
Translation to amino acids → Synthesis of proteins (early proteins followed by late
proteins)
▪ General mechanisms
o DNA viruses replicate in the nucleus except poxviruses
o RNA viruses replicate in the cytoplasm except Orthomyxoviridae and
Retroviridae

5. Assembly of virion/ Maturation

▪ General mechanisms
o Assembly of nucleocapsid
▪ DNA viruses: Happens in the nucleus
▪ RNA viruses: Happens in the cytoplasm except Orthomyxoviridae and
Retroviridae
o Incorporation of the envelope
▪ Glycoproteins
• Protein moiety is synthesized by the virus
• Carbohydrate moiety of the glycoproteins are derived from the
host cell
▪ Lipids are derived from the host cell
▪ Most enveloped viruses: Lipids and carbohydrates are incorporated at the
plasma membrane
• Herpesviridae: Lipids and carbohydrates are incorporated at the
nuclear membrane
• Coronaviridae, Bunyaviridae, and Flaviviridae: Lipids and
carbohydrates are incorporated at the intracytoplasmic
membranes
6. Release of progeny virus
▪ Enveloped
Released by budding through the cell membrane → Senescence of the host cell
▪ Naked
Release causes disintegration of cell membrane and eventual lysis of the host cell

Phases of viral cycle

1. Eclipse period
▪ Period during a virus life cycle between uncoating and maturation
▪ No intact virions are seen within the infected host cell
2. Productive period
▪ Period from the assembly of the virion to the release of the progeny
*** Viral cycles of enveloped viruses are not well-defined.

Virus-Cell Interactions

1. Non-permissive
▪ Attachment is blocked
▪ No assembly and release
2. Abortive
▪ Non-persistent, non-productive infections
▪ Replication process is not completed
▪ Factors
o Presence of a non-permissive cell
o Environmental factors
o Ineffective virus

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 4

 3. Non-persistent, productive infections
▪ Acute infections
▪ Rapid/ Abrupt onset with immediate development
▪ Absence of virions after recovery
4. Persistent infections
▪ Intact virus/ subviral particles remain in the body of the host for a long period of time
▪ Types
Chronic: Virus production continues
Latent: No continuous production; Virus stays at a specific site of latency

Effects on the host cell

1. Cytopathic effects
a. Lysis
b. Cell fusion → Syncytia formation
c. Inclusion bodies
▪ Eosinophilic/ basophilic aggregates of viruses present in the site of replication/
site of assembly
▪ Intracytoplasmic eosinophilic
o Negri bodies in Rabies
o Guarnieri bodies in Small pox
o Bollinger bodies in fowl pox
o Henderson-Peterson bodies in Molluscum contagiosum
▪ Intranuclear acidophilic
o Cowdry Type A in Herpes simplex virus and Varicella zoster virus
infection
o Torres bodies in Yellow fever
o Cowdry Type B in Polio
▪ Intranuclear basophilic
o Cowdry Type B in Adenovirus
o ‘Owl eyes” in Cytomegalovirus infection
▪ Both intranuclear and intracytoplasmic
o Warthin- Finkeldey bodies in Measles
d. Malignant Transformation
▪ Oncogenic viruses
Oncogenic viruses Tumor
EBV Burkitt’s Lymphoma
Nasopharyngeal carcinoma
HPV Cervical Cancer
HBV Hepatocellular carcinoma
Human Herpes Virus Type 8 Kaposi’s Sarcoma
HTLV-1 Adult T-cell leukemia
HTLV-2 Hairy cell leukemia

2. Production of new cell surface antigens

• Associated with enveloped viruses
• Virally encoded proteins are left out in the membrane → Modified host cell membrane →
Host cell considered as “Foreign” →Attacked by cytotoxic T lymphocytes → Cytolysis

Laboratory Diagnosis
1. Microscopy
a. Electron microscopy
Most rapid method of diagnosis
Negative staining technique (most common method for rapid EM)

b. Light microscopy
Observation of cytopathic effects

c. Fluorescence microscopy

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 5

 2. Chicken embryo technique
• Yolk sac inoculation: 5 to 8 days-old embryo
• Amniotic inoculation: 6 to 8 days-old embryo
• Allantoic inoculation: 9 to 12 days-old embryo
• Chorioallantoic inoculation: 9 to 12 days-old embryo
• Embryonic inoculation : 5-12 days of age

3. Cultivation

Cell culture
Primary cell culture
- Cells from mammalian tissue
- Used for isolation of most viruses
- Examples
o Primary monkey kidney cells
o Human embryonic kidney cells
o Rabbit kidney cells

Finite/ diploid cell culture

- Cultures of connective tissue cells
- Only type of cell culture that can be used for isolation of Cytomegalovirus
- Example: Human Neonatal Lung (HNL)

Continuous
- Immortal cell lines; Heteroploid cell line
- Derived from malignant or transformed cells
- Used most commonly for isolation of HSV, RSV, enteroviruses, and
adenoviruses
- Examples
o Hep2: Carcinoma of the human larynx
o HeLa: Human cervical carcinoma
o A549: Human lung carcinoma
o KB: Nasopharyngeal carcinoma

4. Serological tests
a. Neutralization tests
b. Complement fixation tests
c. Hemagglutination inhibition tests

5. Molecular techniques
a. Polymerase chain reaction
b. Blotting techniques (Western blot)

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 6

DNA Viruses

Family Diameter Core Capsid symmetry Presence of envelope

Parvoviridae 18-26 nm (+) ssDNA Icosahedral Naked
Linear
Smallest of
the DNA
viruses Baltimore Classification: Group II

Smallest of
the viral
families
**Formerly 45-55 nm ( + ) dsDNA Icosahedral Naked
Papovaviridae Circular

Papillomaviridae
Baltimore Classification: Group I
Polyomaviridae

Adenoviridae 70-90 nm ( + ) dsDNA Icosahedral Naked

Linear

Baltimore Classification: Group I

Hepadnaviridae 42 nm ( + ) dsDNA Icosahedral Enveloped
Circular; Gapped

Baltimore Classification: Group

VII
Herpesviridae 150- 200 nm ( + ) dsDNA Icosahedral Enveloped
Linear

Baltimore Classification: Group I

Poxviridae 170- 200 X ( + ) dsDNA Complex Enveloped
300-450 nm Linear

Largest of the
DNA viruses Baltimore Classification: Group I

Largest of the
viral families

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 7

RNA Viruses

Family Diameter Core Capsid Presence of envelope

symmetry
Orthomyxoviridae 90-120 nm (-) ssRNA Helical Enveloped
Segmented; 8 segments

Baltimore Classification: Group V

Paramyxoviridae 150-300 nm (-) ssRNA Helical Enveloped
Continuous
Largest
of the RNA
viruses Baltimore Classification: Group V
Rhabdoviridae “Bullet-shaped” (-) ssRNA Helical Enveloped
70-85 x 130- Continuous
380 nm
Baltimore Classification: Group V
Filoviridae Filamentous (-) ssRNA Helical Enveloped
form Continuous
80 X 790-
14,000 nm Baltimore Classification: Group V
Coronaviridae 80-160 nm (+) ssRNA Helical Enveloped
Continuous

Baltimore Classification: Group IV

Bunyaviridae 90-120 nm (-) ssRNA Helical Enveloped
Segmented; 3 segments

Baltimore Classification: Group V

Arenaviridae 50-300 nm (-) ssRNA Helical Enveloped
Segmented; 2 segments

Baltimore Classification: Group V

Picornaviridae 28-30 nm (+) ssRNA Icosahedral Naked
Continuous
Smallest of
the RNA Baltimore Classification: Group IV
viruses
Caliciviridae 35-40 nm (+) ssRNA Icosahedral Naked
Continuous

Baltimore Classification: Group IV

Reoviridae 60-80 nm ( + ) dsRNA Icosahedral Naked
Segmented; 10-12 segments

Baltimore Classification: Group III

Togaviridae 60-70 nm (+) ssRNA Icosahedral Enveloped
Continuous

Baltimore Classification: Group IV

Flaviviridae 40-50 nm (+) ssRNA Icosahedral Enveloped
Continuous

Baltimore Classification: Group IV

Retroviridae 80-130 nm (+) ssRNA Icosahedral Enveloped
2 copies of the genome

Baltimore Classification: Group VI

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 8

IMPORTANT: Viral Taxonomy is constantly changing. While the classification that this table is presenting might be accurate for now, I’m pretty sure it won’t
be the case in a couple of years.
DNA VIRUSES
Virus Clinical Manifestation Natural Reservoir Mode of Transmission Immunization Others
Parvoviridae
Genus Erythrovirus
Parvovirus B-19 Erythema infectiosum Humans and Animals Respiratory,
- Fifth disease) occasionally by blood
- “Slapped cheek rash” transfusion;
transplacental
Aplastic crises in patients with chronic
hemolytic anemias

Fetal infection, Stillbirth

Papillomaviridae
Human papillomavirus (HPV) WARTS Humans and animals
Anogenital warts (condyloma acuminata) Sexual Active immunization:
- HPV 16-18 Subunit (Recombinant
- In females: cervix, vulva, vagina DNA) vaccine
- In males: Penis, urethra

Cutaneous warts
- Common wart (verucca vulgaris) Direct contact or
- Flat warts (verruca planae) through fomites

CERVICAL CANCER
Polyomaviridae
BK polyomavirus Mild asymptomatic primary infection Humans Unknown Was first isolated in the
Hemorrhagic cystitis urine of a renal
Person to person, not transplant patient whose
from an animal source initials was B.K

Studies suggest that

the virus is spread via
respiratory route
JC polyomavirus Mild asymptomatic primary infection Humans Unknown Was first isolated from
Multifocal leukoencephalopathy the brain of a patient with
progressive multifocal
leukoencephalopathy
The initials of the said
patient were J.C.
Adenoviridae
Genus Mastadenovirus
Adenovirus 1-37 Respiratory tract: Pharyngitis, Humans and animals Aerosol droplet
tracheobronchitis, pneumonia Direct contact or by
Eye infection: Epidemic fomites
keratoconjunctivitis (serotype 8)

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 9

 Enteric adenovirus Gastroenteritis Humans and animals Fecal-oral route
40-41
Hepadnaviridae
Genus: NONE established
Hepatitis B virus Hepatitis, cirrhosis, hepatocellular Humans Parenteral, sexual, Active immunization:
carcinoma vertical, infected Inactivated vaccine
secretions (saliva) Recombinant DNA
vaccine

Passive Immunization
Hepatitis B
immunoglobulin
(HBIG)
Herpesviridae
Subfamily Alphaherpesvirinae

Herpes simplex virus Gingivostomatitis Humans Infected oral

Type -1 (HSV-1) secretions
(HHV-1)

Herpes simplex virus Genital infections Humans Infected genital

Type -2 (HSV-2) secretions
(HHV-2)

Varicella-zoster Virus VARICELLA (chicken pox): Humans Respiratory route Active immunization:
(VZV) Fever, rash Attenuated vaccine
(HHV-3) Complications: Secondary bacterial
infection, rash hemorrhage, encephalitis Passive immunization:
Zoster immunoglobulin
ZOSTER (shingles): Reactivation of the (ZIG)
disease
Rash, hyperaesthesia

Subfamily Betaherpesvirinae

Cytomegalovirus HETEROPHILE-NEGATIVE Humans Vertical

(CMV) INFECTIOUS MONONUCLEOSIS (Transplacental,
(HHV-5) Asymptomatic infection, congenital Perinatal), sexual,
disease of the newborn, symptomatic infected secretions
disease of immunocompromised host, (urine, saliva)
Subfamily
Gammaherpesvirinae

Epstein-Barr Virus INFECTIOUS MONONUCLEOSIS Humans Sexual contact

(EBV) - Mono, Kissing disease, Kissing
(HHV-4) Glandular fever
- Fever, pharyngitis,
lymphadenopathy,
splenomegaly

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 10

 Burkitt’s lymphoma in children (4-12 y/o)
Nasopharyngeal carcinoma (20-50 y/o)

Progressive lymphoreticular disease,

oral hairy leukoplakia in HIV-infected
patients

Human herpesvirus 6 Roseola Humans Unknown

(HHV-6) - Sixth disease , Exanthem
subitum, Rosoela infantum

Fever, malaise, rash, leukopenia, and

intestinal pneumonitis in organ transplant
patients
Human herpesvirus 8 Kaposi’s sarcoma Humans Unknown
(HHV-8)
Poxviridae
Genus Orthopoxvirus

Variola virus Smallpox Man Respiratory route or Smallpox Vaccine Only infectious disease
fomites to be completely
eradicated

Vaccinia virus Cutaneous ulcerative lesions Man Respiratory route or

fomites

Monkeypox virus Monkeypox Squirrels and other Intimate Contact JYNNEOS Vaccine
• Rash that may be located near rodents, non-human Direct contact with (effective against
the genitals or anus primates monkeypox rash, Smallpox and
• Rash initially look like pimples Man scabs, body fluids Monkeypox)
or blisters and may be painful or
itchy Touching objects and
• Rash will go through several surfaces that have ACAM2000 vaccine
stages, including scabs, before been used by (alternative; also
healing someone with effective against
• Flu-like symptoms: Fever, monkeypox Smallpox and
Swollen lymph nodes, Chills, Monkeypox)
Headache, Myalgia Contact with
respiratory secretions

Sexual contact,
Kissing, Prolonged
Face-to-Face Contact

Contact (Scratch/
Bites) from infected
animals

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 11

 Genus Parapoxvirus
Orf virus Localized vesiculogranulomatous lesions Sheep, goats Contact with infected
on hand and face anima
Genus Molluscipoxvirus
Molluscum Molluscum contagiosum: Benign nodules Humans Direct person-to-
contagiosum on the skin person contact
Transmission by
fomites

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 12

RNA VIRUSES
Virus Clinical Manifestation Natural Reservoir Mode of Immunization Others
Transmission
Orthomyxoviridae
Genus Influenzavirus
Influenza A Influenza (malaise, headache, Humans Respiratory droplet Known to have the capability of
myalgia, cough) Avians including Person to person undergoing antigenic drift and
poultry and fowl Animal to person Influenza A (H1N1), A antigenic shift
Primary influenza pneumonia Pigs (H3N2), and one or two
In children: Broncholitis, Croup, Other animals influenza B viruses Lipoprotein envelope contains 2
Otitis Media such as horses (depending on the glycoproteins: Hemagglutinin and
vaccine) are included Neuraminidase
Complications: in each year’s influenza • Hemagglutinin (H)
Pulmonary: Secondary bacterial vaccine o 18 different subtypes
infections Active immunization: o Most important
Non-pulmonary: virulence factor
Encephalopathy, Reye’s o Binds to host cells
syndrome, Guillan-Barre a. Live, attenuated • Neuraminidase (N)
syndrome, myocarditis intranasal vaccine (LAIV) o 11 different subtypes
o Hydrolyzes mucus and
assists viral budding
b. Inactivated vaccine- and release
i.m. Nomenclature:
Virus Type/ Geographic origin/
Strain number/ Year of isolation/
Virus subtype

Example:
A/Fujian/411/2002 (H3N2)

Genus Influenzavirus
Influenza B Mild influenza Humans Respiratory droplets Only undergo antigenic drift
Genus Influenzavirus
Influenza C Minor respiratory disease Humans Respiratory droplets Probably not involved in epidemics
Paramyxoviridae
Genus Morbillivirus
Measles virus MEASLES (RUBEOLA) Humans Respiratory droplets Active immunization:
Fever, Koplik’s spots, runny Animals Attenuated vaccine
nose and eyes, maculopapular (MMR)- i.m.
rash
Complications: Subacute
sclerosing panencephalitis
(SSPE), pneumonia,
encephalitis
Genus Pneumovirus URTI and LRTI esp. in infants Humans Transmission by
Respiratory Animals fomites and contact
Syncytial Virus (RSV) with hands-
infectious respiratory
secretions
Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 13
 Genus Henipavirus
Nipah virus Respiratory illness Humans Close contact with
(NiV) Encephalitis: headache, Animals infected bats,
drowsiness, disorientation, Flying infected pigs, and
mental confusion foxes (bats) of from other niV
Pteropus infected people
Swine
Genus Rubulavirus
Mumps virus MUMPS: malaise, fever, Humans Infectious saliva and Active immunization:
parotitis, Animals respiratory Attenuated vaccine
Complications: orchitis, secretions (MMR)- i.m.
oophoritis, meningitis, deafness

Parainfluenza Common cold, Humans Transmission by

virus 1-4 tracheobronchitis, rarely Animals fomites and contact
pneumonia with hand- infectious
respiratory
secretions
Rhabdoviridae
Genus Lyssavirus
Rabies virus RABIES Animals Exposure to Passive immunization: Guidelines for utilization of HRIG
Incubation: 1-2 months Dogs contaminated saliva Human rabies • Consider type of contact
Prodoromal phase: 2-10 days Raccoons via animal bites or immunoglobulin (HRIG) • Category I: Touching/
Fever, cough, sore throat Skunks licking non-intact Feeding animals, licks on
Burning tingling or sensation Coyotes skin the intact skin-- DO NOT
at wound site Foxes Active immunization: NECESSITATE HRIG
Bats Inactivated vaccine • Category II: Nibbling on
Illness a. Human diploid cell skin, Abrasions without
a. FURIOUS PHASE: strain (HDCS)- i.m. bleeding—DO NOT
Agitation, disorientation, b. Semple vaccine- i.m. NECESSITATE HRIG
seizures, twitching, • Category III: Multiple
hydrophobia bites, Exposure to bat
b. DUMB PHASE: scratches and bites---
Paralysis, disorientation, IMMEDIATE WOUND
stupor MANAGEMENT AND
c. COMA PHASE HRIG ADMINISTRATION

• Type of administration
• 5 dose regimen:
Administration of one
dose each at 0,3rd ,7th
,14th , & 30th days
• 2-1-1 regimen:
Administration of 2 doses
at 0 day, 1 dose at 7th
day, and 1 dose at 21st
day
• 2-site intradermal
method: (2-2-2-0-1-1):
Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 14
 2 doses each at 0, 3rd,
and 7th day
1 doses each at 21st &
30th day

Presence of Negri bodies-

pathognomonic sign
Filoviridae
Genus: NONE
Ebola virus Hemorrhagic fever leading to Nonhuman Close contact with ERVEBO (Ebola Zaire
coagulopathy: Overexpression primates infected person or Vaccine)
of procoagulant tissue factor animal

Coronaviridae
Genus Coronavirus
Human coronaviruses

SARS-CoV-1 Severe acute respiratory Humans and Infected respiratory

syndrome (SARS) animals (nasal) secretions

MERS-CoV Acute respiratory syndrome Humans and Infected respiratory

particularly affecting specific animals (camels) (nasal) secretions
Middle Eastern countries

SARS-CoV-2 COVID-19 Humans and Infected respiratory BioNTech and Pfizer

animals (nasal) secretions (mRNA)
Droplet and Airborne Moderna (mRNA)
AstraZeneca
(adenovirus)
Jannsen Pharmaceutica
NV (adenovirus)
Novavax (protein)
Valneva (inactivated
virus vaccine)
Sinovac (inactivated
virus vaccine)
Bunyaviridae
Genus Bunyavirus
(Group C arbovirus) Meningitis as most common Birds Mosquito-borne
California complication Small mammals (Aedes triseriatus)
encephalitis group
including
LaCrosse virus

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 15

 Hanta virus Hemorrhagic fever with renal Deer mice and Exposure to rodent
syndrome: other small excreta
Intense headache, back & mammals
abdominal pain, renal
dysfunction, various
hemorrhagic complications
leading to renal failure

Hantavirus pulmonary
syndrome

Arenaviridae
Genus Arenavirus
Lymphocytic Influenza-like symptoms and Mice and other Contact with urine
choriomeningitis virus meningitis small mammals from mice
(LCM)

Hemorrhagic fever
viruses
Machupo virus Bolivian hemorrhagic fever Mice and other Contact with urine
Junin virus Argentinian hemorrhagic fever small mammals from mice

Lassa virus Lassa hemorrhagic fever: Humans Contact with infected Named after the town in Nigeria
hemorrhages, encephalitis, man where the first cases occurred
multiple organ failure

Picornaviridae
Genus Enterovirus
Poliovirus (3 types) CNS infection Human GIT Fecal-oral route Active immunization
Meningitis, Contaminated
encephalitis &/or myelitis, water Inactivated vaccine
paralysis Human-to-human (IPV)- i.m. (SALK)
Attenuated vaccine
(OPV)- oral (SABIN)

Coxsackie virus Herpangina, hand-foot mouth Human GIT Fecal-oral,

group A disease Conjunctival,
Respiratory

Coxsackie virus Pleurodynia (Bornholm disease, Human GIT Fecal-oral,

group B epidemic myalgia), pericarditis, conjunctival,
and myocarditis respiratory

Genus Hepatovirus
Hepatitis A virus Acute hepatitis and jaundice Human GIT Fecal-oral
(Enterovirus type 72) (contaminated food)

Genus Rhinovirus
Rhinovirus Coryza (Common colds) Human respiratory Infectious aerosols-
(113 types) tract Inhalation, contact

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 with hands,
transmission by
fomites
Caliciviridae
Genus Calicivirus
Hepatitis E virus Hepatitis Human GIT Fecal-oral route Hepatitis similar to that caused by
contaminated water Hepatitis A virus; Extraordinarily
IMPORTANT: Hepatitis E high case fatality rate (10-20%)
virus is now classified under among pregnant women
Family Hepeviridae
Genus Norovirus
Norwalk virus Acute gastroenteritis (AGE): Human GIT Fecal-oral route Norwalk virus has been implicated
Nausea, vomiting, and diarrhea in many cases of cruise ship
outbreaks
Noroviruses are the most common
cause of AGE in the United States
Reoviridae
Genus Rotavirus Gastroenteritis in infants and Human and Fecal-oral route Active immunization:
children 6 months to 2 years animal (birds) GIT Attenuated, oral vaccine

Genus Reovirus Little association with disease Human GIT Fecal-oral\

Genus Orbivirus Colorado tick fever: Human and Tick-borne

Fever, headache, malaise, joint animal GIT (Dermacentor
pains, anorexia, nausea, andersoni)
vomiting, and leukopenia

Togaviridae

Genus Rubivirus
Rubella Virus Rubella/ German Measles / Humans Respiratory droplets Active immunization: Rubella can cause a miscarriage or
Three-day Measles: Attenuated vaccine serious birth defects in a
IMPORTANT: Rubella virus Low-grade Fever, Sore Throat, Transplacental (MMR)- i.m. developing baby if a woman is
is now classified under and a rash that starts on the infected while she is pregnant.
Family Matonaviridae face and spreads to the rest of
the body

Genus Alphavirus
(Group A Arbovirus)
Chikungunya virus Chikungunya: Headache, Humans Mosquito-borne
(chikV) muscle pain, joint swelling, (Aedes aegypti &
rash; Joint pain Aedes albopictus)

Venezuelan equine Encephalitis Birds Mosquito-borne

encephalitis virus
Eastern equine Encephalitis Rabbits, rodents Mosquito-borne
encephalitis virus
Western equine Encephalitis Rodents Mosquito-borne
encephalitis virus

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 Flaviviridae
Genus Flavivirus
(Group B arbovirus)
Dengue fever virus Dengue hemorrhagic fever; Humans Mosquito-borne Dengvaxia Has 5 serotypes (Used to be 4)
“Breakbone disease/ Bone (Aedes aegypti & • Live recombinant Infection with one
crushing disease” Aedes albopictus) tetravalent vaccine serotype confers life-long immunity
Dengue hemorrgahic shock (Serotypes 1-4) against the serotype
syndrome (DHSS) • 3 doses (0/6/12-
month schedule)

Zika virus Many cases are asymptomatic. Humans Mosquito-borne Zika virus can stay longer in semen
Symptomatic: Fever, rash, (There are no (Aedes aegypti & than in any other body fluids.
headache, joint pain, reports of Zika Aedes albopictus)
conjunctivitis, and muscle pain. infecting other Main public health concern is the
animals) (CONTINUED) Congenital Zika syndrome
Complications: Microcephaly in Sexual intercourse
developing foetuses (infection (anal, vaginal, oral)
among pregnant patients) Transplacental

Yellow fever virus Yellow fever- hemorrhagic fever Monkeys Mosquito-borne

affecting the liver and other
viscera

St. Louis encephalitis Meningitis, encephalitis Birds Mosquito-borne

virus

West Nile virus Many asymptomatic cases Humans, birds, Mosquito-borne

(WNV) Symptomatic: fever, muscle horses
pain, encephalitis

Japanese Encephalitis Pigs, wading birds Mosquito-borne Inactivated Vero cell Primarily affects Southeast Asia,
encephalitis virus (Culex culture-derived Japanese East Asia, South Asia, and the
tritaeniorhynchus) encephalitis vaccine Pacific islands
• 2-dose series
• Doses spaced 28
days apart
• Last dose given
at least 1 week
before travel to
endemic area
Genus Hepacivirus
Hepatitis C virus Hepatitis and jaundice Humans Parenteral Strong correlation
(HCV) between chronic HCV
infection and
hepatocellular carcinoma
Retroviridae
Subfamily Oncovirinae
Human T-lymphotropic virus- Adult T-cells leukemia Humans Unknown Hematologic findings include
1 (HTLV-1) presence of Sezary cells

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 Human T-lymphotropic virus- Hairy cell leukemia Humans Unknown Hematologic findings include
2 (HTLV-2) presence of Hairy cells
Subfamily Lentivirinae
Human Immunodeficiency
Virus
HIV-1 Acquired Immunodeficiency Humans Sexual, parenteral Strain is found worldwide and is
Syndrome (AIDS) more common
Stage 1: Asymptomatic phase Strain more likely to progress and
Stage 2: AIDS-related complex worsen
(ARC)- with persistent During progression, HIV-1 has
lymphadenopathy, night sweats, lower CD4 counts
and diarrhea Plasma viral loads are higher
Stage 3: Full-blown AIDS:
variety of opportunistic
infections

Immunodeficiency. Less Humans Sexual, parenteral More predominant in West Africa

HIV-2 pathogenic than HIV-1

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 ANTIGENIC SHIFT

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 20

 ANTIGENIC DRIFT

Danroe Arvee R. Balagat, RMT, MLS(ASCPi)CM Virology 21