Microbiology- Viruses

Paramyxovirus- characteristics

• enveloped, pleomorphic (irregular shape)

• ssRNA (-) (single-stranded, negative-sense RNA)

• causes Measles, Mumps, RSV

• Spread through aerosols— infects respiratory tract

paramyxovirus- key viruses

• Measles virus- causes fever, rash, pneumonia

• Mumps virus- causes swollen salivary glands

• RSV ( Respiratory Syncytial Virus)- causes bronchiolitis in infants

paramyxovirus- structure and replication

• F Protein- helps virus enter cells (fusion)

• HN/H/G proteins- help virus attach to cells

• Replication in cytoplasm, released by budding

adenovirus- characteristics

• non-enveloped (tough and stable)

• dsDNA virus (double-stranded DNA)

• can be lytic (kills cells) or latent (hides in cells)

• spread via air, fecal-oral, fomites

adenovirus- key diseases

• respiratory infections- pharyngitis, pneumonia

• pink eye (conjunctivitis)- red, irritated eyes

• gastroenteritis- stomach flu

adenovirus- structure and replication

• fibers- help the virus attach to cells

• enters via endocytosis, replicates in nucleus

• new viruses lyse (burst) the host cell

picornavirus- characteristics

• non-enveloped, small and tough

• ssRNA (+) (single-stranded, positive-sense RNA)

• replicates in cytoplasm

• spread via fecal-oral, inhalation

picornavirus- key viruses

• Poliovirus— causes paralysis

• Coxsackie A/B viruses— Hand-Foot-Mouth Disease (blisters)

• Rhinovirus— causes the common cold

• Hepatitis A virus— liver infection

picornavirus- structure and replication

• virus attached to host ribosomes to make proteins

• uses RNA polymerase to copy its genome

• lytic virus- kills host cell when new viruses are released

coronavirus- characteristics

• enveloped, helical shape

• ssRNA (+) virus

• causes respiratory infections

coronavirus- key diseases

• Common Cold—sneezing, sore throat

• SARS & MERS— severe lung infection

• COVID-19— fever, cough, breathing problems

coronavirus- structure and replication

• spike proteins (S proteins)- help virus attach to cells

• uses ACE2 receptor for infection (SARS-CoV-2)

• replicates in cytoplasm, released by exocystosis

Mumps Virus

Family: Paramyxovirus

Transmission: Respiratory droplets

Incubation: 12-29 days
Symptoms: Swollen parotid glands, fever, headache
Complications: Orchitis, oophoritis, meningitis, pancreatitis
Vaccine: Live attenuated (MMR vaccine)

Rubella (German Measles)

Family: Togavirus
Transmission: Respiratory droplets
Incubation: 14-21 days
Symptoms: Mild fever, faint macular rash, lymphadenopathy
Complications: Congenital rubella syndrome (CRS) → deafness, cataracts, heart defects
Vaccine: Live attenuated (MMR vaccine)

Picornaviruses

Includes: Enteroviruses (Poliovirus, Coxsackie, Echovirus, Rhinovirus), Hepatitis A
Type: ssRNA (+), Non-enveloped, Icosahedral
Transmission: Fecal-oral route (except Rhinovirus, which is respiratory)
Resistant to: Acid, bile, detergents → survives GI tract

Enteroviruses

Includes: Poliovirus, Coxsackie A/B, Echovirus
Transmission: Fecal-oral
Diseases:

• Poliovirus: Paralysis

• Coxsackie A: Hand-foot-mouth disease

• Coxsackie B: Myocarditis, pleurodynia

• Echovirus: Aseptic meningitis

Hepatitis A (HAV)

Family: Picornavirus
Transmission: Fecal-oral (contaminated food, water, shellfish)
Symptoms: Fever, anorexia, nausea, jaundice

Chronic infection? No
Prevention: Hep A vaccine

Hepatitis B (HBV)

Family: Hepadnavirus (Partial dsDNA)
Transmission: Blood, sex, perinatal
Symptoms: Fatigue, jaundice, liver damage
Chronic infection? Yes
Complications: Cirrhosis, Hepatocellular carcinoma
Vaccine? Yes (HBsAg antigen)

Hepatitis C (HCV)

Family: Flavivirus
Transmission: Blood (IV drugs, transfusions, sex)
Chronic infection? Yes (80% cases)
Complications: Cirrhosis, Hepatocellular carcinoma
Vaccine? No (high mutation rate)

Hepatitis D (HDV)

Family: Delta virus (RNA (-))
Needs HBV to replicate
Transmission: Blood, sex, perinatal
Complications: Severe liver damage if co-infected with HBV

Prevention: HBV vaccine (since HDV needs HBV to infect)

Hepatitis E (HEV)

Family: Hepevirus (RNA (+))
Transmission: Fecal-oral (contaminated water, undercooked meat)
Chronic infection? No
Risk: High mortality in pregnant women
Vaccine? No

Paramyxoviruses

Virus Type: Enveloped, helical, single-stranded RNA
Includes: Measles, Mumps, Parainfluenza, RSV
Transmission: Respiratory droplets
Key Features: Membrane fusion for cell entry, released by budding

Mumps Virus

Type: Paramyxovirus
Symptoms: Fever, painful swelling of parotid glands
Complications: Meningitis, encephalitis, orchitis
Transmission: Respiratory droplets
Vaccine: Live attenuated (MMR)

Measles Virus

Type: Morbillivirus (Paramyxovirus)
Symptoms: Fever, cough, conjunctivitis, Koplik spots, rash
Complications: Encephalitis, pneumonia, SSPE (rare)
Transmission: Respiratory droplets
Vaccine: Live attenuated (MMR)

Rubella Virus

Type: Togavirus
Symptoms: Mild fever, rash, swollen lymph nodes
Complications: Congenital rubella syndrome (if infected during pregnancy)
Transmission: Respiratory droplets
Vaccine: Live attenuated (MMR)

Picornaviruses

Virus Type: Small, non-enveloped, single-stranded RNA (+)
Includes: Poliovirus, Coxsackievirus, Hepatitis A, Rhinovirus
Transmission: Fecal-oral (except Rhinovirus—respiratory)
Resistant to: Harsh conditions, acid, detergents

Hepatitis Viruses

HAV: Fecal-oral, no chronic infection
HBV: Blood/sex, DNA virus, can cause chronic infection
HCV: Blood, RNA virus, high mutation rate, chronic infection common
HDV: Needs HBV to replicate
HEV: Fecal-oral, dangerous in pregnancy

Herpesviruses

Virus Type: Enveloped, dsDNA, icosahedral
3 Subfamilies:

• Alpha: HSV-1, HSV-2, VZV

• Beta: CMV, HHV-6, HHV-7

• Gamma: EBV, HHV-8
  📌 Latency: Hides in nerve or immune cells

Herpes Simplex Virus (HSV-1 & HSV-2)

HSV-1: Oral herpes (cold sores), encephalitis
HSV-2: Genital herpes, neonatal infections
Latency: Nerve ganglia
Reactivation triggers: Stress, fever, sun exposure

Varicella-Zoster Virus (VZV/HHV-3)

Primary Infection: Chickenpox (rash, fever)
Reactivation: Shingles (painful rash along nerves)
Latency: Dorsal root/cranial nerve ganglia
Transmission: Respiratory droplets, direct contact
Vaccine: Live attenuated

Epstein-Barr Virus (EBV/HHV-4)

Disease: Infectious mononucleosis ("kissing disease")
Symptoms: Fatigue, swollen lymph nodes, fever
Associated with: Burkitt’s lymphoma, nasopharyngeal carcinoma
Latency: B cells

Cytomegalovirus (CMV/HHV-5)

Transmission: Blood, sexual, congenital, organ transplant
Symptoms: Mononucleosis-like illness, severe in newborns & immunocompromised
Latency: Monocytes, endothelial cells

HHV-6 & HHV-7

Disease: Roseola (high fever, rash in infants)
Latency: CD4+ T cells
Transmission: Saliva

Kaposi’s Sarcoma-associated Virus (HHV-8)

Disease: Kaposi’s sarcoma (cancer in AIDS patients)
Latency: B cells
Transmission: Saliva, blood

Influenza- What type of genome does the influenza virus have?

It is a negative-sense single-stranded RNA (-ssRNA) virus.

How many segments are in the genome of Influenza A and B?

8 segments.

Where does the influenza virus replicate inside the host cell?

In the nucleus (unusual for an RNA virus).

Where does influenza virus assembly and release happen?

At the plasma membrane.

What part of the body does influenza typically infect?

A: The upper respiratory tract epithelium.

What is the shape of the influenza virus?

Pleomorphic (flexible envelope) with a helical nucleocapsid.

What enzyme does influenza use to replicate its RNA?

RNA-dependent RNA polymerase.

What is the role of the (+)RNA strand in influenza replication?

It acts as a template for protein synthesis and making more (-)RNA.

Where does packaging of new viral RNA take place?

In the nucleus.

What is the function of Hemagglutinin (HA)?

It helps the virus attach to and enter host cells.

Q: What is the function of Neuraminidase (NA)?

It helps the virus leave the host cell by cleaving sialic acid.

What does the M2 protein do?

Acts as an ion channel and helps with viral uncoating.

What is the role of M1?

Structural matrix protein.

What do PB1, PB2, and PA do?

They are parts of the viral RNA polymerase complex.

What does NP (nucleocapsid protein) do?

It binds and protects the viral RNA.

What is the role of NS1 protein?

Blocks the host's interferon response (immune evasion).

What does NS2 do?

Helps move new viral components out of the nucleus.

What type of genome do Paramyxoviruses have?

Single-stranded negative-sense RNA (ssRNA−), linear genome.

What are the three main genera of Paramyxoviruses?

A: Morbillivirus, Paramyxovirus, Pneumovirus.

What diseases do Paramyxoviruses cause?

Measles, Mumps, RSV, Parainfluenza.

How are Paramyxoviruses transmitted?

By aerosols (coughs/sneezes), infect the respiratory tract.

Are Paramyxoviruses stable in the environment?

No, they are very labile—easily destroyed by heat, detergents, UV light, and acid.

What virus is in the Morbillivirus genus?

Measles virus (single serotype).

What viruses are in the Paramyxovirus genus?

Mumps virus (single serotype), Parainfluenza viruses 1–4.

What viruses are in the Pneumovirus genus?

Respiratory Syncytial Virus (RSV), Human Metapneumovirus.

How do Paramyxoviruses enter cells?

By membrane fusion (via the F protein).

How are Paramyxoviruses released from cells?

By budding.

What does the NP protein do?

Binds and protects the viral RNA.

What is the function of the P protein?

Assists in RNA replication.

What is the L protein?

RNA-dependent RNA polymerase.

What does the F protein do?

Promotes fusion with the host cell and causes syncytia formation.

What does the M protein do?

Helps with viral assembly (matrix protein).

What attachment protein does Measles virus use?

H (Hemagglutinin) — binds MCP and SLAM receptors.

What attachment protein do Mumps and Parainfluenza use?

HN (Hemagglutinin-Neuraminidase) — binds sialic acid.

What attachment protein does RSV use?

G (Glycoprotein) — binds sialic acid but is not a hemagglutinin.

Is Adenovirus an enveloped virus?

No, it's non-enveloped (more stable in the environment).

What type of genome does Adenovirus have?

Double-stranded DNA (dsDNA), linear.

Where does Adenovirus replicate and assemble?

In the host cell nucleus.

How many Adenovirus types are there, and which are most common?

52 types; types 1–7 are most common in infections.

What happens in permissive vs. non-permissive cells?

Permissive: lytic infection; Non-permissive: latent or persistent infection.

What are Adenoviruses used for in biotechnology?

Gene therapy, cancer therapy, and studying RNA splicing.

What structures help Adenovirus attach to host cells?

Fiber proteins on capsid vertices.

Which receptors does Adenovirus bind to?

CAR (Coxsackie-Adenovirus Receptor) and MHC I.

How does Adenovirus enter cells?

Receptor-mediated endocytosis.

What is the function of E1A and E1B proteins?

Inhibit p53 and Rb (tumor suppressors).

What is the function of E2 protein?

Encodes viral DNA polymerase.

What does the E3 region do?

Suppresses the immune response and blocks apoptosis.

What does the E4 region prevent?

Apoptosis (cell death).

How is Adenovirus transmitted?

Inhalation, close contact, oral-fecal route, fomites, and pools.

What is a hallmark of Adenovirus infection in cells?

Inclusion bodies without cell enlargement.

Name three diseases Adenovirus can cause.

A: Pharyngitis, conjunctivitis, gastroenteritis.

What type of genome do picornaviruses have?

Single-stranded RNA (+)

Can picornavirus RNA be directly translated?

Yes, it acts like mRNA and binds directly to host ribosomes

What enzyme does picornavirus use to replicate its genome?

RNA-dependent RNA polymerase (encoded by the virus)

Where does picornavirus replication occur?

In the cytoplasm.

What are the main groups of picornaviruses?

Enteroviruses, Rhinoviruses, Cardioviruses, Aphthoviruses, and Hepatovirus (hepatitis A virus)

Name 3 enteroviruses.

Poliovirus, Coxsackie A and B viruses, Echovirus

What virus causes Hepatitis A?

Hepatitis A virus (a type of hepatovirus).

What is the most common cause of the common cold?

Rhinovirus.

What receptor does rhinovirus use to infect cells?

ICAM-1.

Can rhinoviruses survive in the stomach?

No, they are not acid-resistant and can't survive the GI tract.

How is rhinovirus transmitted?

Through aerosols (inhalation) and fomites (contaminated surfaces).

Where do rhinoviruses primarily replicate?

In the nasal cavity.

What is the structure of Coronaviruses?

• Enveloped virus

• Helical (spiral) genome

• Single-stranded RNA (+)

• Spikes form a crown shape ("corona")

What role do the spike proteins in Coronaviruses play?

• Help the virus survive acidic environments like the stomach

• Assist in attaching to and entering host cells

What part of the body do Coronaviruses typically infect?

• Infect the upper respiratory tract (nose, throat)