DNA Viruses - Microbiology

Adenoviruses:
Transmission:
Respiratory, fecal-oral, and direct contact (eye).
Site of latency:
Replication in oropharynx.
Disease:
Acute respiratory disease, Pharyngitis, pharyngoconjunctival fever, keratoconjunctivitis, pneumonia, hemorrhagic cystitis, disseminated disease, and gastroenteritis in children.
Diagnosis:
Cell culture (HEp-2 and other continuous human epithelial lines), enzyme immunoassay (EIA) for gastroenteritis serotypes 40-41.
Prevention:
Vaccine (adenovirus serotypes 4 and 7) for military recruits.
Note:
Adenoviruses has a role as vectors in gene therapy, deliver DNA for gene replacement therapy in few genetic disorders, such as cystic fibrosis.
Non-enveloped. All DNA viruses replicate in the nucleus, except Poxvirus which replicate in the cytoplasm.
The only viruses having a fiber protruding from each of the 12 vertices of the capsid.

1. DNA viruses

2. A. A denoviridae 1. Adenoviruses: Transmission : Respiratory, fecal -oral, and direct contact (eye). Site of latency: Replication in oropharynx . Disease : Acute respiratory disease, Pharyngitis, pharyngoconjunctival fever, keratoconjunctivitis, pneumonia, hemorrhagic cystitis, disseminated disease, and gastroenteritis in children. Diagnosis: Cell culture (HEp-2 and other continuous human epithelial lines), enzyme immunoassay (EIA) for gastroenteritis serotypes 40-41. Prevention: Vaccine (adenovirus serotypes 4 and 7) for military recruits. Note: A denoviruses has a role as vectors in gene therapy , deliver DNA for gene replacement therapy in few genetic disorders , such as cystic fibrosis . Non-enveloped. All DNA viruses replicate in the nucleus , except Poxvirus which replicate in the cytoplasm. The only viruses having a fiber protruding from each of the 12 vertices of the capsid.

3. B. Hepadnaviridae ( H epadnavirus ) 1. Hepatitis B virus (HBV): Transmission: Humans are reservoir and vector; spread by direct contact, including exchange of body secretions, recipient of contaminated blood products, percutaneous injection of virus, and perinatal exposure. Site of latency: Liver . Disease: Acute infection with resolution (90%); fulminant hepatitis, most coinfected with delta virus (1%); chronic hepatitis, persistence of hepatitis B surface antigen (HBsAg) (9%) followed by resolution (disappearance of HBsAg), asymptomatic carrier state, chronic persistent (systemic disease without progressive liver disease), or chronic active disease (progressive liver damage). Liver cirrhosis. Oncogenic Liver cancer . Diagnosis: Serology, viral antigen detection, and polymerase chain reaction (PCR). AST, ALT and Bilirubin. Prevention: HBV vaccine; hepatitis B immune globulin. Note: E nveloped virus.

4. Australian antigen (HBsAg)

5. C. Herpesviridae (Herpesvirus (HSV), enveloped) 1. HSV-1 and HSV-2: Transmission: direct contact with infected secretions . Site of latency Sensory nerve ganglia. Disease: predominant virus in parentheses: gingivostomatitis (HSV-1), pharyngitis (HSV-1), herpes labialis (HSV-1), genital infection (HSV-2), conjunctivitis (HSV-1), keratitis (HSV-1), herpetic whitlow (HSV-1 and HSV-2), encephalitis (HSV-1 in adults), disseminated disease (HSV-1 or HSV-2 in neonates). Detection: cell culture (HDF, others), EIA, FA stain, IH stain, PCR . 2. Varicella zoster virus (VZV): Transmission: close personal contact, especially respiratory . Site of latency: d orsal root ganglia. Disease: chicken pox (varicella), shingles (zoster), a belt of roses from Hell. Detection: FA stain, cell culture (HDF), shell vial culture, PCR. Prevention: Vaccine .

6. 3. Epstein–Barr virus (EBV): Transmission : Close contact with infected saliva. Site of latency: B lymphocytes . Disease: Infectious mononucleosis, progressive lymphoreticular disease, oral hairy leukoplakia in patients with HIV. Oncogenic Burkitt lymphoma, nasopharyngeal carcinoma. Detection: Serology, Paul–Bunnell (heterophil Ab test-IgM), Monospot test (RBCs are more specific for acute infectious mononucleosis heterophile antibodies), PCR .

7. 4. Cytomegalovirus ( CMV): Transmission: c lose contact with infected secretions, blood transfusions (WBCs), organ transplants, transplacental . Site of latency WBCs, endothelial cells, cells in a variety of organs. Disease: Asymptomatic infection, congenital disease of newborn , symptomatic disease of immunocompromised host (pneumonia), heterophile-negative infectious mononucleosis. Diagnosis: Cell culture (HDF), shell vial culture, CMV antigenemia, FA stain, PCR . 5. HHV-6 and HHV-7: Transmission: Most likely close contact via respiratory route; almost all children infected by age 2-3 years. Site of latency: T lymphocytes (CD4 cells) . Disease: Roseola (exanthem subitum ), fever, malaise, rash, leukopenia, and interstitial pneumonitis in organ transplant recipients. Detection: d etection of virus in peripheral blood specimens by PCR, cell culture using lymphocyte lines . 6. HHV-8: Transmission: Not known; much less widely disseminated than other herpes viruses . Site of latency: Viral genome found in Kaposi tumor cells, endothelial cells, and tumor -infiltrating leukocytes. Disease: Kaposi sarcoma . Detection: PCR or in situ by hybridization.

8. D. Papovaviridae Papillomavirus 1. Human papilloma virus (HPV): Transmission: Direct contact, sexual contact for genital warts. Site of latency: Epithelial tissue . Disease: Papilloma : benign tumors of squamous cells or s kin and genital warts, benign head and neck tumours, anogenital warts. Diagnosis: Cytology, DNA probes . Oncogenic: Cervical and penile cancer (especially HPV types 16 and 18 ). Note: Non-enveloped.

9. E . Polyomaviridae Polyomavirus 1. Polyomavirus (BK virus [BKV] and JC virus [JCV] infect humans). Transmission: Probably direct contact with infected respiratory secretions; both viruses are ubiquitous in humans. Site of latency: Kidney . Disease: Mild or asymptomatic primary infection; virus remains dormant in kidneys; reactivation in immunocompromised patients causes hemorrhagic cystitis (BKV) or progressive multifocal leukoencephalopathy (JCV). Detection: JCV by polymerase chain reaction (PCR) (cerebrospinal fluid) or electron microscopy (EM) (brain tissue); BKV by PCR or cytology (urine). Note: Non-enveloped .

10. F. Parvoviridae Parvovirus 1. Parvovirus B-19: Transmission: Close contact, probably respiratory . Disease: Erythema infectiosum (fifth disease), aplastic crises in patients with chronic hemolytic anemias ( ertyhrovirus ) , and fetal infection and stillbirth. Detection: Serology, polymerase chain reaction (PCR), histology. Note: The smallest of the DNA. Non-enveloped.

11. G. Poxviridae Poxviruses 1. Smallpox (Variola), molluscum contagiosum, O rf , and monkeypox viruses: Transmission: Respiratory droplets (smallpox); direct contact (molluscum contagiosum, O rf , monkeypox). Disease: All are diseases of the skin; smallpox is a generalized infection with pustular rash (10%-25% fatal); molluscum contagiosum manifests as benign nodules; O rf manifests as localized papules/vesicles; monkeypox manifests as a generalized infection that includes the skin. Detection: Electron microscopy (EM) of material from a skin lesion; polymerase chain reaction (PCR). Prevention: Vaccine for smallpox; avoid contact for all viruses. Note: The largest and most complex viruses.

12. RNA viruses

13. A. Arenaviridae Arenaviruses Transmission: From rodent to human through contamination of human environment with rodent urine; virus enters through skin abrasions or inhalation. Disease: LCM causes asymptomatic to influenza like to aseptic meningitis–type disease; Lassa fever virus causes influenza-like disease to severe haemorrhagic fever. Diagnosis: Serology, polymerase chain reaction. Note: Enveloped. Pleomorphic, Sandy appearance. All RNA viruses replicate in cytoplasm , except  Orthomyxoviruses and Retroviruses  that have replicative stages in nuclei .

14. Bunyaviridae Bunyavirus, Hantavirus, Nairovirus , and Phlebovirus . Transmission: Mosquito (Aedes), tick, and sandfly vectors, except for hantaviruses, which are zoonoses transmitted by contact with rodent host and/or their excretions. Disease: Encephalitis for arboviruses; pneumonia or hemorrhagic fever for hantaviruses. Phlebovirus : Rift V alley f ever (RVF). Diagnosis: Serology and antibody detection in cerebrospinal fluid, reverse transcriptase polymerase chain reaction (RT-PCR) for hantaviruses (serology [IgM and IgG]) also available for hantavirus (sin nombre virus). Note: Triple-segmented and a single-stranded RNA . Enevloped . All these viruses, with the exception of hantaviruses, are arboviruses that are transmitted by mosquitoes, ticks, and flies. Hantaviruses, transmitted by rodents.

15. Calciviridae Calciviruses Norovirus (Norwalk virus) Transmission: Fecal -oral. Disease: Nausea, vomiting, and diarrhoea. Norwalk, most common cause viral gastroenteritis in adults. The infection typically occurs in group settings, such as schools, hospitals, nursing homes. Diagnosis: EM, RT-PCR, EIA for noroviruses . Note: Naked nonenveloped viruses.

16. Coronaviridae Coronaviruses Transmission: Probably direct contact or aerosol. Disease: Common cold; possibly gastroenteritis, especially in children; Severe acute respiratory syndrome (SARS). Diagnosis: EM, RT-PCR. Note: Crown-like appearance . Enveloped. The second most important cause of the common cold; rhinoviruses being the first cause.

17. Filoviridae Filoviruses ( Ebola virus and Marburg virus) Transmission: Transmissible to humans from monkeys and, presumably, other wild animals; human-to-human transmission via body fluids and respiratory droplets. Disease: Severe haemorrhage and liver necrosis; mortality as high as 90%. The most pathogenic of the haemorrhagic fever viruses. Diagnosis: Electron microscopy, cell culture in monkey kidney cells; Biosafety Level 4 required. RT-PCR, ELISA. Note: Filo: threadlike. Enveloped. Marburg hemorrhagic fever virus displays the characteristic “shepherd’s hook” morphology.

18. Flaviviridae Flaviviruses ( yellow fever virus, dengue virus, and St. Louis encephalitis virus), arboviruses. Hepatitis C virus (HCV). Transmission: Arthropod vector, usually mosquito. Disease: St. Louis and West Nile encephalitis, dengue and yellow fever. Jaundice. Diagnosis: Serology and antibody detection in cerebrospinal fluid; reverse transcriptase polymerase chain reaction (RT-PCR) for dengue and yellow fever. Note: Enveloped.

19. Hepatitis C virus (HCV) Transmission: Parenteral, blood donation, perinatal, or sexual. Disease: Acute and chronic hepatitis; strong correlation between chronic HCV infection and hepatocellular carcinoma. Liver cirrhosis. Diagnosis: Serology, RT-PCR, and viral genotyping . Recombinant immunoblot assay (RIBA) using recombinant HCV antigen is a highly specific test to detect HCV infection. Also NAAT (RNA). Note: The most important cause of parenteral non-A, non-B hepatitis (NANBH) worldwide.

20. Hepiviridae Hepevirus HEV Transmission: Fecal -oral. Disease: Hepatitis similar to that caused by hepatitis A virus except for extraordinarily high case fatality rate (10%-20%) among pregnant women. Diagnosis: Serology . Note: Previously classified in the family of caliciviruses. Non-enveloped.

21. Orthomyxoviridae Orthomyxovirus 1. Influenza A: Transmission: Contact with respiratory secretions . Disease: Influenza (fever, malaise, headache, myalgia, cough); primary influenza pneumonia; in children, bronchiolitis, croup, otitis media. Detection: Cell culture (PMK), EIA, FA stain, RT-PCR. Epidemiology: Viral subtypes based on hemagglutinin and neuraminidase glycoproteins abbreviated “H” and “N,” respectively (e.g., H1N1 or H3N2); infects humans and other animals; antigenic drift, resulting in minor antigenic change, causes local outbreaks of influenza every 1-3 years; antigenic shift, resulting in major antigenic change, causes periodic worldwide outbreaks. Prevention: Influenza vaccine or antiviral prophylaxis .

22. 2. Influenza B: Transmission: Contact with respiratory secretions . Disease: Similar to “mild” influenza. Detection: Cell culture (PMK), EIA, FA stain, RT-PCR . Epidemiology: Antigenic drift only, resulting in local outbreaks every 1-3 years. Prevention: Influenza vaccine or antiviral prophylaxis . 3. Influenza C: Transmission: Contact with respiratory secretions . Disease: Mild form of influenza causing URTIs. Detection: Testing not routinely requested, so virus is infrequently detected; only valid test is NAAT . Epidemiology: Most cases occur in children; occurs sporadically or as localized outbreaks.

23. Paramyxoviridae Paramyxoviruses 1. Measles virus: Transmission: Contact with respiratory secretions; extremely contagious . Disease: Measles, atypical measles (occurs in those with waning vaccine immunity), and subacute sclerosing panencephalitis. Detection: Cell culture (PMK) and serology . Prevention: Measles vaccine. 2. Mumps virus : Transmission: Person-to-person contact, presumably respiratory droplets. Disease: Mumps . Detection: Cell culture (PMK) and serology. Prevention: Mumps vaccine .

24. 3. Parainfluenza virus: Transmission: Contact with respiratory secretions . Disease: Adults: upper respiratory disease, rarely pneumonia, Children: respiratory including croup, bronchiolitis, and pneumonia. Detection: Cell culture (PMK), shell vial culture, and FA stain . 4. Respiratory syncytial virus (RSV): Transmission: Person-to-person by hand and respiratory contact . Disease: Primarily in infants and children. Infants: bronchiolitis, pneumonia, and croup. Children: upper respiratory disease. Detection: Cell culture (HEp-2), EIA, and FA stain . Epidemiology: Disease occurs annually late fall through early spring; nosocomial transmission can occur readily.

25. Picornaviridae Picornaviruses Picornaviruses ( pico : small) are the smallest viruses , measuring 20–30 nm in size. They are nonenveloped. 1. Enteroviruses 2. Poliovirus (3 types) 3. Coxsackie virus, group A (23 types) 4. Coxsackie virus, group B (6 types) 5. Echovirus (31 types) Transmission: Fecal -oral . Disease: Predominant virus in parentheses: polio (poliovirus); herpangina (coxsackie A); pleurodynia (coxsackie B); aseptic meningitis (many enterovirus types); handfoot -mouth disease (coxsackie A); pericarditis and myocarditis (coxsackie B); acute hemorrhagic conjunctivitis (enterovirus 70); and fever, myalgia, summer “flu” (many enterovirus types), neonatal disease (echoviruses and coxsackie viruses). Detection: Cell culture (PMK and HDF), PCR, and serology. Prevention: Avoid contact with virus; vaccination for polio.

26. 6. Hepatitis A virus (enterovirus type 72): Transmission: Fecal -oral . Disease: Acute hepatitis with short incubation, abrupt onset, and low mortality; no carrier state. Detection: Serology . LFT. Prevention: Vaccine; prevent clinical illness with serum immunoglobulin. 7. Rhinovirus (common cold virus) : Transmission: Contact with respiratory secretions. Disease: Common cold . Detection: Cell culture (usually not clinically necessary), RT-PCR.

27. Reoviridae Reovirus Rotavirus Transmission: Fecal -oral; survives well on inanimate objects. Disease: Gastroenteritis in infants and children 6 months to 2 years. Detection: Enzyme immunoassay (EIA), latex agglutination (LA). Prevention: Avoid contact with virus; vaccination .

28. Retroviridae Retroviruses 1. Human immunodeficiency virus types 1 and 2 (HIV-1, HIV-2). Transmission: Sexual contact, blood and blood product exposure, and perinatal exposure . Site of latency: CD4 T lymphocytes. Disease: Most disease in humans caused by HIV-1; infected cells include CD4 (helper) T lymphocytes, monocytes, and some cells of the central nervous system; asymptomatic infection, acute flulike disease, acquired immunodeficiency syndrome (AIDS)–related complex, and AIDS-associated infections and malignancies. Detection: Serology, antigen detection, reverse transcriptase polymerase chain reaction (RT-PCR) . Those at risk of infection are homosexual or bisexual males, intravenous drug abusers, sexual contacts of individuals infected with HIV, and infants of infected mothers. 2. Human T-lymphotropic viruses types 1 and 2 (HTLV-1, HTLV-2). Transmission: Known means of transmission are similar to those for HIV . Disease: T-cell leukemia and lymphoma, and tropical spastic paraparesis for HTLV-1; no known disease associations for HTLV-2. Detection: Serology . Oncogenic: T-cell lymphoma (HTLV-1).

29. Rhabdoviridae Rhabdovirus Rabies virus Transmission: Bite of rabid animal most common; 20% of human rabies cases have no known exposure to rabid animal. Disease: Rabies . Detection: Fluorescent antibody (FA) staining, polymerase chain reaction (PCR). CPE (Negri bodies). Prevention: Avoid contact with rabid animals; vaccinate domestic animals; post-exposure prophylaxis with hyperimmune antirabies globulin and immunization with rabies vaccine.

30. Togaviridae Togaviruses 1. Rubella virus: Transmission: Respiratory, transplacental . Disease: Rubella (mild), congenital rubella. Detection: Serology . Prevention: Rubella vaccine. 2. Arboviruses referred to as alphaviruses: Transmission: Arthropod vector, usually mosquito . Disease: Eastern, Western, and Venezuelan equine encephalitis. Detection: Serology and antibody detection in cerebrospinal fluid (CSF).

31. First marker that appears in HBV: HBsAg. HCV confirmed by RIBA (Recombinant Immunoblot assay). HDV: Only HBsAg positive patients are tested for HDV, HDV-Ag is the first marker, IgM anti-HDV appears next followed by low levels of IgG anti-HDV.

32. Alyazeed Hussein, BSc, SUST This has been a presentation of Alyazeed Hussein Thanks for your attention and kind patience @elyazeed7 @Alyazeed7ussein