Untitled Quiz

Picornaviruses

• Very small in size, smallest of the RNA viruses (Pico = small).
• Are non-enveloped ssRNA viruses that display icosahedral symmetry.
• Replication occurs in the cytoplasm.
• Causes granulation and rounding of infected cells in tissue culture, known as CPE.

Foot and Mouth Disease (FMD) Virus

• It is a highly infectious disease that affects cattle, sheep, pigs, and goats.
• Transmission occurs to humans through contact with infected animals, or by ingesting contaminated meat, milk, or milk products.
• Fever, salivation, and vesicles on the mucous membrane of the oropharynx and on the skin of the palms, soles, fingers, and toes are the clinical signs.

Orthomyxoviruses

• "Ortho" means direct, and "Myxo" means mucous.
• These viruses have a direct affinity for the mucous membrane.

Influenza viruses

• Influenza viruses have three antigenic types: A, B, and C.
• Virions are pleomorphic, meaning they can be spherical or filamentous.
• The genome is ssRNA and segmented, consisting of 8 segments in types A and B, and 7 segments in type C.
• It is enveloped with 2 types of spikes, haemagglutinin (HA) and neuraminidase (NA).
• Antigenic variation is common due to changes in HA and NA.

Haemagglutinin (HA)

• There are 16 types in animals and 8 types in humans.
• Rod-shaped and functions by attaching the virus to cell surface receptors (sialic acid) allowing entry into the cells.
• Stimulates a protective neutralizing antibody immune response.
• Agglutinates human and Chicken RBCs in the laboratory in the Haemagglutination assay.

Neuraminidase (N)

• There are 9 types in animals and 6 in humans.
• It is mushroom-shaped and facilitates virus release from infected cells during budding and degrades the protective mucous layer.

Antigenic Variation

• Common with antigenic changes in HA and NA in influenza viruses.

Antigenic Shift (Major Ag Variation)

• Major antigenic changes happen from genome reassortment between different virus strains and occurs only for influenza A.
• Occurs infrequently, about every 10 years.
• Influenza B is predominantly a human virus and does not undergo an antigenic shift.

Antigenic Drift (Minor Ag Variation)

• Accumulation of mutation in the gene causes amino acid changes in the protein.
• Occurs every year leading to local outbreaks of influenza A and B.

Genetic Re-assortment

• Segments are exchanged between the segmented nucleic acid of two different strains of viruses infecting a single cell.
• Some of the progeny viruses will contain a mix of gene segments from both strains.

Influenza Pathogenesis

• Infection happens by droplets and contact with contaminated hands or surfaces.
• The virus multiplies in the respiratory tract, causing rhinitis, pharyngitis, and bronchitis.
• The disease is self-limited.
• Can be complicated by viral or bacterial pneumonia due to H. influenzae, Strept. pneumoniae, and Staph. aureus, mainly in the elderly.

Influenza Prophylaxis

• Inactivated vaccine containing two types of strain A and one type of strain B is produced every year.
• The vaccine is only protective in 70% of cases and immunity is short-lasting, as antigenic variations occur causing emergence of new strains not present in the vaccine.
• The vaccine is reformulated yearly to contain current antigenic strains.
• Yearly boosters in October are recommended for the elderly, those with chronic diseases, or those who wish to reduce their risk of acquiring influenza.

Paramyxoviruses Properties

• Enveloped ssRNA viruses.
• Genome is linear and non-segmented.
• Has 2 types of spikes: haemagglutinin (HA) and fusion (F) glycoprotein, which mediates membrane fusion.

Mumps Virus (Infectious Parotitis)

• Generalized viral disease characterized by fever, swelling, and tenderness of the parotid, and sometimes the submaxillary glands.
• Droplet infection and direct contact with saliva and urine are modes of transmission.
• Incubation period ranges from 12-18 days.
• Prevented with live attenuated mumps virus vaccine, given with measles and rubella (MMR).
• Given in 2 doses S/C, one at 15 months and the second before school entry, provides long-lasting, permanent immunity after a single infection.
• The presence of only one stable antigenic type and the neutralizing antibodies (IgM and IgG) that are formed, makes it protective.

Measles Virus

• Disease is characterized by prodromal fever, conjunctivitis, cough, and Koplik's spots.
• Koplik's spots are bluish-white ulcers in the buccal mucosa opposite the upper molars.
• Maculopapular rash appears all over the body after the fever subsides.
• Droplet infection and direct contact are the modes of transmission.
• Can be prevented with live attenuated measles virus vaccine, as part of the MMR vaccine.
• This is given in 2 doses S/C, one at 15 months of age and the 2nd just before school entry and gives immunity.
• Long-lasting immunity occurs after a single infection, due to presence of only one stable antigenic type and the neutralizing antibodies (IgM and IgG) formed.

Postnatal Rubella

• Transmitted from person to person by droplet infection.
• Incubation ranges from 2-3 weeks.
• Clinically characterized by low-grade fever, malaise, maculopapular rash and joint pain.
• Viremia develops after 7-9 days & lasts for 13-15 days leads to the development of antibodies as the rash fades.
• IgG antibodies persist for life and provide lifelong immunity.

Congenital Rubella Syndrome

• It is caused by transplacental transmission of infection to the fetus.
• Causes a high rate of congenital anomalies that may end with fetal death or abortion.
• Rubella is a mild self-limited illness.
• Prevention and control can be achieved through living attenuated rubella virus vaccine alone or in combination with measles and mumps (MMR).

Retroviruses

• Enveloped ssRNA viruses.
• The envelope is a lipid bilayer.
• Contain the reverse transcriptase (RT) enzyme, which converts the RNA into DNA.
• Human immunodeficiency virus (HIV), the cause of AIDS, is the most important member of this family.

Human Immunodeficiency Virus (HIV)

• HIV causes Acquired Immunodeficiency Syndrome (AIDS)
• The virus is ssRNA.
• The cone-shaped capsid is made of a protein called p24.
• The core contains the viral genome and reverse transcriptase.
• The envelope is a lipid bilayer with viral glycoprotein projection called gp 160.
• Transmitted through: blood transfusion, sexual intercourse, contaminated syringes, from mother to infant, and contaminated tattoo needles.
• HIV kills CD4+ cells, resulting in suppression of cell-mediated immunity.
• The CD4+ cells fuse with neighboring uninfected cells, followed by lysis of large numbers of fused cells and a rapid fall of CD4+ helper cell count below 200 cells/μl.
• Severe immune suppression due to HIV causes AIDS.
• The virus reduces immune response within the oral cavity and this promotes oral opportunistic infections and tumours.
• Among the most common are Periodontal disorders of poly microbial origin

HIV/AIDS Prevention and Control

• Blood screening in blood banks to exclude positive samples
• Careful blood handling and tissue specimens
• Use disposable syringes
• Avoid sharing toothbrushes and razors
• Thoroughly sterilize dental and surgical instruments
• Safely discard contaminated needles
• Immediate administration of antiviral drugs to staff with skin pricks accidents
• HIV infected pregnant females should deliver by caesarean section
• Vaccination is under trials.

Coronaviridae Properties

• Enveloped, helical, ssRNA viruses
• Hemagglutinin molecules make up peplomers on the virus surface, giving it a sun-like shape
• The second most common cause of the common cold.
• Birds and small mammals are the reservoir.
• Transmitted through respiratory droplets
• SARS and atypical pneumonia are diseases caused.
• Clinical case definition includes fever, flu-like illness, dry cough, dyspnoea, and progressive hypoxia.
• Chest x-rays show patchy distribution of focal interstitial infiltrates.

SARS Transmission

• Exposing to respiratory droplets, from symptomatic or asymptomatic individuals harboring the virus
• Airborne transmission with aerosol-generating procedures
• Fomite transmission from contamination of inanimate surfaces.

COVID-19 Immunization Types

• For active immunization through Vaccination: RNA Vaccines (Moderna, Pfizer); Viral Vector vaccines (Oxford/AstraZeneca, Gamalaya-Sputnik); Inactivated Virus (SinoVac, SinoPharm)
• For passive immunization, using Antibody Administration.

Approved Corona Virus Vaccines

• Pfizer-BioNTech COVID-19 Vaccine
• Moderna COVID-19 Vaccine
• AstraZeneca Vaccine
• Sinopharm's COVID-19 vaccine
• Sinovac COVID-19 Vaccine