Viruses

Question 1

List the DNA and RNA viruses

Answer 1

DNA viruses (HHAPPP)

1. Herpesvirus
2. Hepadnavirus
3. Adenovirus
4. Pox virus
5. Papillomavirus
6. Polyoma virus
7. Parvovirus

RNA Viruses:

1. Arena virus , Astro virus
2. Bunyavirus
3. Calici virus, corona virus
4. Delta (HepD)
5. Hepatitis E
6. Flavivirus
7. Orthomyxovirus
8. Paramyxovirus
9. Reovirus, Rhabdovirus, Retrovirus
10. Toga virus

Question 2

Describe Mumps virus- Classification, disease, lab diagnosis and vaccine

Answer 2

• It is a Paramyxovirus
• It is the m/c cause of parotid enlargement in children
• Mumps:
  1) Transmission: Resp droplets/saliva/fomites
  2) Incubation period= 7-23 days
  3) Clinical features:
  
  • Asymptomatic/Non specific symptoms -more common in adults
  • Bilateral parotitis (70-90%)
  • Epididymo orchitis
  • Aseptic meningitis, Pancreatitis
  • Atypical mumps (meningitis without parotitis)
• Lab Diagnosis:
  1) Buccal swab
  2) Antigen detection (direct IF on specimen)
  3) Viral isolation (primary monkey kidney CL)
  4) Ab detection (ELISA)
  5) PCR
• MMR vaccine: Live attenuated
  2 doses (1 year, 4-6 years)
  -Jeryl Lynn strain is used

Question 3

List the Clinical manifestations of herpes simples virus (HSV).

Answer 3

There are 3 stages- Primary infection, latent infection and recurrent infection.
Recurrent infection is less severe and often asymptomatic .
Clinical manifestations are:
1. Orofacial lesions
- m/c primary lesion = gigivostomatitis and pharyngitis
- m/c recurrent lesion = herpes labialis
-others: ulcerative stomatitis or vesicular lesions in eyelids

2. Cutaneous lesions:
   a) Herpetic whitlow - Fingers of HCWs
   b) Febrile blisters
   c) Herpes Gladiatorum - trunks of wrestlers
   d) Eczema herpeticum - HSV in patient with chronic eczema
   e) Erythema multiforme - Target lesions are seen

Other Infective Syndromes:

a) CNS - Meningitis/Bell’s palsy/encephalitis
b) Ocular - keratitis, corneal ulcers
c) Genital - mainly by HSV-2
d) Viremia
e) Neonatal herpes

Question 4

Describe influenza virus— Classification, Genera and Subtypes, Antigenic variation, Disease.

Answer 4

Influenza viruses are Orthomyxoviruses.
They have:
- Segmented (-)ve sense ss-RNA 
- Helical symmetry
- Enveloped

Genera based on M1 matrix protein and Nucleoprotein: Influenza A,B and C

Subtypes of Influenza A based on HA and NA proteins:

• H types: 18
• N types: 11

Human infection:
H1,2,3,5,7,9
N1,2

Antigenic variations:

1. DRIFT: Gradual, minor change, due to accumulation of point mutations
2. SHIFT: Drastic, major change due to Genetic reassortment (New strain produced from two strains infecting single host cell, which is antigenically unrelated to parent strains)

Disease: IP= 18-72 hours

1. Uncomplicated Influenza (Flu)- Fever, chills, runny nose,headache , sore throat and cough
2. Complications
   a) Respiratory: Pneumonia, Otitis media, sinusitis
   b) Extrapulmonary: Myositis (m/c), Myocarditis, Pericarditis, Encephalitis, Reye’s Syndrome

Question 5

Dengue fever, DHF, DSS clinical criteria.

Answer 5

Dengue fever (DF): An acute febrile illness with two or more of the following manifestations: Headache, retro-orbital pain, myalgia, arthralgia, rash, hemorrhagic manifestations.

Dengue hemorrhagic fever (DHF): Clinical criteria of dengue fever plus hemorrhagic tendencies evidenced by one or more of the following:

1. Positive tourniquet test
2. Petechiae, ecchymoses or purpura
3. Bleeding from mucosa, GI tract, injection sites etc
4. Thrombocytopenia, more than 20% drop in haematocrit after volume replacement treatment compared to baseline
5. Signs o f plasma leakage (pleural effusion, ascites etc)

Dengue shock syndrome (DSS): All the above criteria for DHF with evidence of circulatory failure, like:

• rapid and weak pulse
• narrow pulse pressure (mm Hg)
• hypotension for age
• cold and clammy skin
• restlessness

Question 6

What is the window period of HIV?

Answer 6

-Following HIV infection, detectable levels of antibodies appear only after a period of interval called the window period.
This is about 3-12 weeks after infection.
- The window period can be as low as 22 days when we use sensitive 3rd gen ELISA kits.

• During the window period, most conventional screening tests are not useful.
• Rather, p24 antigen (12-26 days after infection) detection or HIV RNA (10-14 days) detection can be done

Question 7

Can Measles cause CNS infection?

Answer 7

Children below <2 years affected by primary measles infection are prone to developing CNS infection as a complication. Most commonly it causes SSPE.
Other CNS complications: Post-measles encephalomyelitis, Inclusion body encephalitis.

Onset: 7-14 years after primary infection
Symptoms: Progressive intellectual deterioration, seizures, ataxia, visual disturbances. Hugh mortality within 3 years (10-20% mortality)

Diagnosis: CSF analysis

• High titre of immunoglobulin in CSF
• Viral antigen detection
• Viral genome amplification by PCR
• Cultivation of virus

No effective treatment is available.

Question 8

Stages of measles infection.

Answer 8

1. Incubation period = 10 days
2. Prodromal stage = 4 days (From day 10th-14th)
   - Fever
   - Koplik spots (Day 12th)
   - Non specific symptoms like Coryza, cough, etc.
3. Eruptive stage (After day 14th) - Maculopapular rashes. Behind ears—> face—> trunk and limbs
4. Post Measles stage - Weakness, weight loss