ALLPOX: PATHOGENESIS AND CLINICAL MANIFESTATIONS

The causative agent of smallpox is the variola virus, an orthopoxvirus within the Poxviridae family. Smallpox is a contagious disease characterized by fever and a vesicular and pustular rash.
Pathogenesis
Smallpox is readily transmitted from person to person via droplet nuclei, aerosols, or direct contact with contaminated fomites. Transmission generally occurs after the onset of the rash. Infection begins once the virus implants onto the oropharyngeal or respiratory mucosa. It passes rapidly into local lymph nodes and multiplies. An asymptomatic viremia ensues, followed by multiplication of the virus in the reticuloendothelial system. The virus then localizes in the oropharyngeal mucosa and dermal blood vessels.
Clinical Manifestations
After the usual 12- to 14-day incubation period (range, 7-17 days), the patient typically presents with high fever, malaise, headache, and backache. Severe abdominal pain may also be present. The characteristic rash usually begins 2 to 3 days after symptom onset. The rash is maculopapular and appears on the oropharyngeal mucosa, face, and forearms. It then spreads to the trunk and legs. Within 2 days, the rash becomes vesicular then pustular. Scabs usually appear on the eighth or ninth day of the rash, and pitted scarring develops. There may be a second, less pronounced temperature spike 5 to 8 days after the onset of the rash, particularly if there is secondary bacterial infection.
The World Health Organization has described five types of smallpox:
- Variola major – The mortality rate in this most common form of smallpox is 30%.
- Variola minor – The disease is milder, and the mortality rate is less than 1%.
- Hemorrhagic smallpox – Frank bleeding can be seen in the skin and mucous membranes. This form of smallpox, which occurs in less than 3% of cases, is fatal within 6 days of appearance of the rash. Pregnant women are unusually susceptible.
- Malignant smallpox – Confluent, flat, velvety lesions (no pustules) are seen in this variant of smallpox, and the case fatality rate exceeds 95%.
- Variola sine eruptione – This form of smallpox, which occurs in previously vaccinated contacts, results in mild symptoms such as low-grade fever, headache, or malaise.
*210/348/5*

ALLPOX: PATHOGENESIS AND CLINICAL MANIFESTATIONSThe causative agent of smallpox is the variola virus, an orthopoxvirus within the Poxviridae family. Smallpox is a contagious disease characterized by fever and a vesicular and pustular rash.
PathogenesisSmallpox is readily transmitted from person to person via droplet nuclei, aerosols, or direct contact with contaminated fomites. Transmission generally occurs after the onset of the rash. Infection begins once the virus implants onto the oropharyngeal or respiratory mucosa. It passes rapidly into local lymph nodes and multiplies. An asymptomatic viremia ensues, followed by multiplication of the virus in the reticuloendothelial system. The virus then localizes in the oropharyngeal mucosa and dermal blood vessels.
Clinical ManifestationsAfter the usual 12- to 14-day incubation period (range, 7-17 days), the patient typically presents with high fever, malaise, headache, and backache. Severe abdominal pain may also be present. The characteristic rash usually begins 2 to 3 days after symptom onset. The rash is maculopapular and appears on the oropharyngeal mucosa, face, and forearms. It then spreads to the trunk and legs. Within 2 days, the rash becomes vesicular then pustular. Scabs usually appear on the eighth or ninth day of the rash, and pitted scarring develops. There may be a second, less pronounced temperature spike 5 to 8 days after the onset of the rash, particularly if there is secondary bacterial infection.The World Health Organization has described five types of smallpox:- Variola major – The mortality rate in this most common form of smallpox is 30%.- Variola minor – The disease is milder, and the mortality rate is less than 1%.- Hemorrhagic smallpox – Frank bleeding can be seen in the skin and mucous membranes. This form of smallpox, which occurs in less than 3% of cases, is fatal within 6 days of appearance of the rash. Pregnant women are unusually susceptible.- Malignant smallpox – Confluent, flat, velvety lesions (no pustules) are seen in this variant of smallpox, and the case fatality rate exceeds 95%.- Variola sine eruptione – This form of smallpox, which occurs in previously vaccinated contacts, results in mild symptoms such as low-grade fever, headache, or malaise.*210/348/5*

Share and Enjoy:
  • Digg
  • Sphinn
  • del.icio.us
  • Facebook
  • Google Bookmarks
  • Blogplay
  • LinkedIn
  • Reddit
  • StumbleUpon
  • Twitter
  • Yahoo! Bookmarks

Random Posts

This entry was posted in Anti-Infectives. Bookmark the permalink.

Comments are closed.