Viral Diseases

 

DNA Viruses

 

Genome/Size

Family

Important Genera

Diseases

SS DNA, nonenveloped, 18-25 nm

Parvoviridae

Human parvovirus B19

Erythema infectiosum, fifth disease (from a 1905 list of skin rash diseases: 1. measles 2. scarlet fever 3. rubella 4. Filatow-Dukes disease 5. erythema infectiosum 6. Roseola infantum) Mild flu-like symptoms, facial rash, maculopapular rash on trunk and limbs.

DS DNA nonenveloped 70-90 nm

Adenoviridae

Mastadenovirus

Respiratory infections in humans, some cause tumors in animals.

DS DNA nonenveloped 40-57 nm

Papovaviridae

Papillomavirus (HPV-16)

 

 

 

Polyomavirus

Warts, some sexually transmitted. HPV-16 associated with close to 90% of cervical cancers, especially serious in South Carolina.

 

Polyoma and simian viruses cause tumors in animals.

DS DNA enveloped 200-350 nm

Poxviridae

Variola major

 

 

Vaccina

Smallpox, (pox – vesicopustular skin eruptions).

 

Cowpox

DS DNA enveloped 150-200 nm

Herpesviridae

Simplexvirus (Herpes simplex 1 and 2; Human herpes virus, HHV-1 and HHV-2)

 

 

 

Varicella zoster (HHV-3)

 

 

 

 

 

 

 

 

 

 

 

 

Lymphocryptovirus (HHV-4; Epstein-Barr)

 

 

 

 

 

Cytomegalovirus (HHV-5)

 

 

 

 

 

 

 

 

 

Roseolovirus
(HHV-6)

 

 

 

HHV-7

 

 

HHV-8

HSV 1 – usually oral transmission, lesions on upper body (cold sores); HSV 2 – usually transmitted genitally, infections of lower body. Lesions appear as sores after cell lysis. Virus persists in latent state and is fairly easily reactivated (UV exposure, fever, radiation, stress).

 

Primary infection is chicken pox, may be accompanied by pneumonia and encephalitis in immuno-compromised children; more severe in adults, usually accompanied by pneumonia. Shingles (zoster) - virus remains dormant in dorsal root or cranial nerve ganglia, reactivated by stress, travels down nerve fiber and causes painful blisters in the relevant dermatome. Unexposed people can contract chicken pox from zoster lesions but not vice versa; primary exposure imparts immunity to exogenous infection.

 

Infectious mononucleosis – malaise and lethargy, pharyngitis, lymph node enlargement, spleenomegaly, fever. Infects B cells and is associated with Burkitt’s lymphoma (lymphoma of head and neck) and nasopharyngeal carcinoma.

 

Usually inapparent, chronic, latent. Estimated 80% of the population carries the virus. Disease appears usually when host is immunocompromised and severity of disease correlates with severity of immunosuppression. Symptoms include pneumonia, hepatitis, mononucleosis, and arthritis. Risk of graft rejection increases significantly with CMV infection.

 

Roseola infantum (sixth disease, exanthem subitum) High fever, generalized rash, rapid and complete recovery

 

Infects most infants, causes measleslike rashes

 

Causes Kaposi’s sarcoma (seen in immunocompromised individuals, primarily AIDS patients)

DS DNA enveloped 42 nm

Hepadnaviridae

Hepadnavirus (Hepatitis B virus)

Serum hepatitis – hepatitis B, may cause hepatocellular carcinoma

 

 

RNA Viruses

 

Genome

Family

Virus

Disease

SS RNA, + strand

nonenveloped

28-30 nm

Picornaviridae

Poliovirus

 

 

 

Coxsackie B virus

 

 

Hepatitis A virus

 

 

Rhinovirus

Polio; loss of anterior horn cells (motor neurons), flaccid paralysis, sometimes of diaphragm

 

Post-viral fatigue syndrome (PVFS), chronic fatigue syndrome

 

Acute hepatitis, 90% recovery, fecal-oral inoculation

 

Common cold

SS RNA, + strand

nonenveloped

35-40 nm

Calciviridae

Norwalk Agent

 

Hepatitis E virus

Gastroenteritis

 

Enterically transmitted non-A, non-B hepatitis

SS RNA,

+ strand enveloped 60-70 nm

Togaviridae

Alphavirus

 

 

Rubivirus(rubella)

Transmitted by arthropods, eastern and western equine encephalitis.

 

German measles; respiratory transmission, causes rash, imparts long-lasting immunity. Especially dangerous to 1st trimester fetuses.

SS RNA,

+ strand enveloped

40-50 nm

Flaviviridae

Flavivirus (an arbovirus; transmitted by mosquito bites)

 

 

 

 

 

 

 

Hepatitis C virus

Yellow Fever: a classic viral hemorrhagic fever. Hepatic necrosis, jaundice, fever, vomiting, diarrhea, mortality rate of 80%; Yellow fever prohibited significant colonization of large parts of South and Central America until controlled (elimination of mosquito population); Panama canal was discontinued until the disease was controlled. Vaccine is now available.

 

Blood-borne non-A non-B hepatitis

SS RNA,

+ strand enveloped

(Order = Nidovirales)

80-160 nm

Coronaviridae

Coronavirus

Upper respiratory infections, common cold; SARS.

(Order = Mono-negavirales)

SS RNA

- strand

enveloped

70-180 nm

Rhabdoviridae

Lyssavirus (rabiesvirus)

Rabies: Zoonotic, transmission by contact with infected animals. Virus spreads from wound to brain along neurons. Incubation is 1 week to 1 year depending on site of wound. Symptoms include cerebral hyperirritability, rage, pharyngeal muscle spasm, alternating mania and coma until death, usually by respiratory failure (destruction of respiratory center. Vaccine available, treatment includes injection with immune globulin and vaccine.

(Order = Mono-negavirales)

SS RNA

- strand

enveloped

80-14,000 nm

Filioviridae

Filovirus (Marburg virus, Ebola virus)

Viral hemorrhagic fever, both initiate from contact with infected monkeys or tissues, may be passed secondarily by contact with secretions or unsterilized instruments. Human-human contact inefficient. Acute fever, muscle pain, abdominal pain, rash, severe gastrointestinal bleeding, generalized hemorrhage, shock, death. Ebola has a mortality rate of close to 90%.

(Order = Mono-negavirales)

SS RNA

- strand

enveloped 150-300 nm

Paramyxoviridae

Rubulavirus

 

 

 

 

 

 

 

Morbillivirus

 

 

 

 

 

 

 

Pneumovirus

Mumps. Half of infections are inapparent. Invades upper respiratory tract and lymph nodes, spreads to target organs (most common is parotid gland). Can cause orchitis (testicular inflammation) in post-pubescent males, may result in sterility. Vaccine available.

 

Red measles: Transmission by inhalation usually, spreads to lymph nodes, infects T-cells. Antibody titer rises, rash appears (probably immune complex mediated hypersensitivity), fever, cough, conjunctivitis. Recovery is usually rapid, complete, and imparts lifelong immunity.

 

Human respiratory syncytial virus

SS RNA
- strand
32 nm

Deltaviridae

Hepatitis D

Requires coinfection with hepatitis B virus

RNA – strand segmented (multiple strands)

80-200 nm

Orthomyxoviridae

Influenza viruses

Influenza: Types A, B, and C. Segmented genome allows extensive recombination leading to antigenic changes. Transmitted by inhalation, infects respiratory mucosa, allows secondary bacterial infections to occur after epithelial denudation.

SS RNA – strand
segmented
90-120 nm

Bunyaviridae

Bunyavirus

Hemorrhagic fevers and Hantavirus pulmonary syndrome

SS RNA – strand
segmented
110-130 nm

Arenaviridae

Arenavirus

Lymphocytic choriomeningitis, Venezuelan hemorrhagic fever, Lassa fever

DS RNA nonenveloped
60-80 nm

Reoviridae

Reovirus

Rotavirus

Mild respiratory infections

Gastroenteritis

DS RNA + strands

Retroviridae:

Oncoviruses:

HTLV I, HTLV II

 

Lentivirus (HIV)

 

Leukemia

 

AIDS

Viral reverse transcriptase makes DNA copy of viral RNA genome which incorporates permanently into host genome