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

About author

Himanshu Paneru’s journey in the world of medical sciences led him to create DOC NOTE MASTER, a platform where education meets expertise. Having earned his Master’s in Medical Microbiology from Netaji Subhash Chandra Bose Subharti Medical College, Dehradun, Uttarakhand, he is dedicated to making medical knowledge more accessible through his writing.