Thursday, January 24, 2008

Possible Viral Agents Part 3

1) Adenoviruses- Serotypes 3, 4, 7
What are adenoviruses?
Adenoviruses can replicate and produce disease in the respiratory, gastrointestinal and urinary tracts and in the eye. Many adenovirus infections are subclinical and may persist in the host for months.

Mode of transmission:

  • Direct contac
  • Respiratory droplet
  • Fecal-oral route
Pathogenesis: Adenoviruses infect and replicate in epithelial cells of the respiratory and gastrointestinal tracts, urinary bladder and liver. They usually do not spread beyond the regional lymph nodes.

Clinical syndrome:
  • Respiratory diseases: cough, nasal congestion, fever and sore throat
  • Eye infections: acute conjunctivitis
  • Gastrointestinal disease: gastroenteritis
Laboratory diagnosis:
Polymerase Chain Reaction (PCR) assays in which primers from a conserved viral sequence can detect all serotypes of adenovirus infections in tissue samples or body fluids.
Serological methods such as the Complement Fixation (CF) test can be used to detect complement-fixing antibodies to adenovirus group antigens.

Epidemiology: Adenoviruses exist in all parts of the world. They are present year-round and usually do not cause community outbreaks of disease. Respiratory disease due to types 3, 4 and 7 is common among military recruits.

Treatment: No specific treatment

Prevention and control:
  • Careful hand washing
  • Disinfect environment surfaces with sodium hypochlorite
  • Use of paper towels
2) Hepatitis viruses- Hepatitis A virus (HAV)
What are HAV?

HAV is a distinct member of the picornavirus family.

Mode of transmission:
  • Fecal-oral route
  • Close contact
Pathogenesis: The virus replicates in the hepatocytes and interferes with normal liver function. The individual’s immune system is then activated to produce a specific reaction to combat the infectious agent. As a result, the liver becomes inflamed.

Clinical syndrome:
  • Jaundice
  • Fever
  • Fatigue
  • Gastrointestinal symptoms: abdominal pain, loss of appetite, nausea, vomiting and vomiting
Laboratory diagnosis:
Immune electron microscopy is used for the detection of HAV in stool and liver preparations.
Sensitive serological assays such as ELISA and PCR methods are used to measure specific HAV antibodies.

Epidemiology: HAV is widespread throughout the world. Outbreaks of type A hepatitis are common in families, institutions, summer camps, day care center, neonatal intensive care units and among military troops.

Treatment: Viral vaccines and protective immune globulin preparations against HAV

Prevention and control:
  • Hands washing after using the bathroom, changing a diaper, and before preparing and eating food.
  • Use own personal products
3) Poxviruses- Monkeypox virus
What is monkey virus?
Monkeypox virus is a species of Orthopoxvirus. The disease was first recognized in captive monkeys in 1958.

Mode of transmission: Direct contact with primary hosts (eg. rodents. Monkeys)

Pathogenesis:Monkeypox virus replicates in lymphoid tissue and localizes in mononuclear phagocytic cells. It is then release into the bloodstream, and then localizes again in skin cells.

Clinical syndrome: Similar to that of smallpox with the exception of enlargement of the cervical and inguina lymph nodes.

Laboratory diagnosis:
Direct examination of clinical materials under electron microscope is used for rapid identification of virus particles.
Antibody assays such as ELISA or RIA can be used as confirmatory tests.

Epidemiology: The disease is a rare zoonosis that has been detected only in remote villages in tropical rain forests.

Treatment: Vaccination with vaccinia

Prevention and control: Vaccinia vaccination is recommended for laboratory workers who directly handle cultures or animals infected with monkeypox virus.

4) Paramyxoviruses- Mumps virus
What is Mumps virus?
Mumps virus mostly causes a mild childhood disease, but in adults complications including meningitis and orchitis are fairly common. More than one-third of all mumps infections are asymptomatic.

Mode of transmission:
  • Direct contact
  • Air-borne droplets
Pathogenesis: Primary replication occurs in nasal or upper respiratory tract epithelial cells. Viremia then disseminates the virus to the salivary glands and other major organ systems.

Clinical syndrome:
  • Swell and pain of the paratid glands
  • Fever
  • Headache
  • Loss of appetite

Laboratory diagnosis:
Immunofluorescence using mumps-specific antiserum can detect mumps virus antigens as early as 2-3 days after inoculation of cell cultures in shell vials.
ELISA is useful because it can detect mumps-specific IgM antibody or mumps-specific IgG antibody.

Epidemiology: Cases appear throughout the year in hot climates. Epidemics may occur in army camps.

Treatment: No specific therapy

Prevention and control: Immunization with attenuated live mumps virus vaccine

5) Herpes Simplex Viruses- Epstein-Barr Virus (EBV)
What is EBV?
EBV is the causative agent of acute infections mononucleosis and lymphoproliferative disorders in immunodeficient individuals.

Mode of transmission:

  • Respiratory secretions
  • Infected saliva
Pathogenesis: Viral replication occurs in epithelial cells of the pharynx and salivary glands. Infected B cells spread the infection from the oropharynx throughout the body. Following primary infections, the virus persists in a latent form in the B lymphocytes of the host. Periodic reactivation of the virus is associated with shedding of virus in saliva.

Clinical syndrome:
  • Infectious mononucleosis: headache, fever, malaise, fatigue and sore throat
  • Oral hairy leukemia: wart like growth on the tongue
  • Lymphoma
Laboratory diagnosis:
Nucleic acid hybridization is the most sensitive means of detecting EBV in patient materials.
Common serologic procedures for detection of EBV antibodies include ELISA tests, immunnoblot assays and indirect immunofluorescence tests using EBV-positive lymphoid cells.

Epidemiology: EBV is common in all parts of the world. In industrialized nations, more than 50% of EBV infections are delayed until late adolescence and young adulthood.

Acycloir reduces EBV shedding from the oropharynx during the period of drug administration.
Adoptive transfer of EBV-reactive T cells shows results of acceptable treatment for EBV-related lymphoproliferative disease.

Prevention and control: No EBV vaccine available

1) Adenovirus- under ELectron Microscopy> image search> adenovirus

2) Hepatitis A virus (HAV)- under Electron Mircoscopy> image search> hepatitis A virus

3) Monkeypox virus> image search> monkeypox virus

4) Mumps virus> image search> mumps virus

5) Epstein-Barr virus (EBV)- in the nucleus of a mammalian cell> image search> epstein-barr virus

1) Geo.F.Brooks, Janet S.Butel, Stephen A.Morse. (2004). Medical Microbiology. Asia: The McGraw-hill Companies.

2) Centers for Disease Control and Prevention. Viral Hepatitis A. (2007). Retrieved 22nd January 2008, from

3) Stanford Education Group. Monkeypox virus. (2000). Retrieved 22nd January 2008, from

4) Medicine Net. Mumps. (2007). Retrieved 22nd January 2006, from

Tham Wan Jin June

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