POXVIRUS

• Poxvirus is the largest & the most complex virus among all virus.

• Poxviruses are classified within the family Poxviridae, which is divided into two subfamilies: Chordopoxvirinae and Entomopoxvirinae.

CLASSIFICATION

• Poxvirus Viruses are grouped into eight genera. Species that cause human infections fall under four genera. Important members include:

  • Variola virus: Causative agent of smallpox, first disease that eradicated from the world.

  • Vaccinia virus: Used as the basis for the smallpox vaccine, it does not cause smallpox but provides immunity against it.

  • Molluscum contagiosum virus: Causes molluscum contagiosum, a skin disease in humans characterized by skin lesion.

VARIOLA VIRUS (SMALLPOX)

MORPHOLOGY

• Shape:

  • brick-shaped

• Size:

  • approx. 200 to 300 nanometers (nm)in diameter.

  • Visible under light microscopy due to their size.

• Symmetry:

  • Complex symmetry

  • Envelope:

  • Envelope present made up of two lipoprotein membrane.

• Genome:

  • Double-stranded DNA genome.

  • Large genome with numerous genes.

  • Molecular weight of the genome is about 108

• Variability:

  • Exhibits some variability in size and shape among different poxvirus species.

PATHOGENESIS

• Variola virus is responsible for smallpox, a highly contagious and often fatal disease that has affected humans.

• Smallpox is Acute exanthematous disease.

• Smallpox was the first disease to be eradicated from the world.

• Last variola major case seen in 1975 in Bangladeshi women in Assam (India), while last minor case seen in Somalia in 1977.

  Ø Mode of transmission:

  • By blood product

  • Cough or sneeze

  • By skin to skin contact

  • Touching contaminated surface

  Ø Route pf transmission:

  • Through respiratory tract

  • Direct contact

  Ø Incubation period:

  • Infection with variola virus begin with an incubation period usually lasting between 10 to 14 days.

  Ø Spread:

  step1 - Virus enter through inhalation or inoculation on the skin

  step2 - Multiply in lymphoid tissue

  step3 - Enters the blood (primary viremia)

  step4 - Reach internal organ & multiplies

  step5 - Re-enters into blood (secondary viremia)

  step6 - Spread to the skin

Symptoms

• symptoms associated with smallpox caused by Variola virus include:

  • High Fever

  • Malaise

  • Diarrhea

  • Vomiting

  • Nausea

  • Pustules

LABORATORY DIAGNOSIS

• Common laboratory methods used for the diagnosis of poxvirus infections include:

  1. Specimen:

  • Saliva

  • Vesicular fluid

  • Scabs

  • Urine

  • Conjunctival fluid

  2. Electron microscope:

  • Brick shape appearance but this method is less common now a days.

  3. Isolation:

  • They grow in chorioallanroic membrane(CAM) of chick embryo & in tissue culture.

  • However, due to the high level of contagiousness & the absence of ongoing smallpox cases, this method is not commonly used.

  4. Serological test:

  • Serological tests such as enzyme-linked immunosorbent assay (ELISA) or other immunoassays, can be employed to detect antibodies specific to the Variola virus in patient serum.

  5. Molecular test:

  • PCR can be used to amplify and detect viral DNA. This method is highly sensitive and specific.

  6. Immunohistochemistry:

  • Immunohistochemistry involves using specific antibodies to detect viral antigens in tissue samples.

  • This method can be applied to skin lesions or other biopsy specimens.

TREATMENT

• Smallpox is a viral infection caused by the Variola virus. The disease has been eradicated globally & routine smallpox vaccination is no longer performed. However if smallpox were to re-emerge or be intentionally released then the general guideline for the treatment of smallpox included:

  1. Isolation: Infected individuals would be isolated in specific area to prevent the spread of the virus to others.

  2. Infection Control Measures: Strict infection control measures would be implemented to minimize the risk of transmission.

  3. Antiviral Medications: There is no specific antiviral drug approved for treating smallpox.

  4. Vaccination: Vaccination provides immunity to the individual & has been highly effective in preventing smallpox.

PROPHYLAXIS

• The primary method used for prophylaxis smallpox was vaccination.

# vaccinia virus - https://docnotemaster.in/vaccinia-virus