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Categorizing viral infections by the organ system most commonly affected (eg, lungs, GI tract, skin, liver, CNS, mucous membranes) can be clinically useful, although certain viral disorders (eg, mumps) are hard to categorize. Many specific viruses and the disorders they cause are also discussed elsewhere in The Manual.
Respiratory infections
The most common viral infections are probably URIs. Respiratory infections are more likely to cause severe symptoms in infants, the elderly, and patients with a lung or heart disorder.
Respiratory viruses include influenza viruses (A, B, C), parainfluenza viruses 1 through 4, adenoviruses, respiratory syncytial virus, and rhinoviruses (see Table 1: Viruses: Some Respiratory Viruses and see Respiratory Viruses). They are typically spread from person to person by contact with infected respiratory droplets.
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Table 1
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| Some Respiratory Viruses |
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Principal Syndromes
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Prevalence and Distribution
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Specific Therapy
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Specific Prevention*
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Influenza viruses A, B, and C
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Influenza
AFRD
Acute bronchitis and pneumonia
Croup
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A and B: Epidemic, occasionally pandemic
C: Endemic
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A: Amantadine or rimantadine
A and B: Oseltamivir or zanamivir
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A and B: Vaccine, oseltamivir or zanamivir
A: Amantadine and rimantadine
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Parainfluenza viruses 1–4
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AFRD (children)
Acute bronchitis and pneumonia
Croup
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1: Local epidemics
1, 2, and 3: Widespread in children
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None
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Vaccines under investigation
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Adenoviruses
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AFRD (children)
Acute respiratory disease (adults)
Acute pharyngoconjunctival fever
Epidemic keratoconjunctivitis
Viral pneumonia
Acute follicular conjunctivitis
Diarrhea
Hemorrhagic cystitis
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Global
Mostly children
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None
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Vaccine containing types 4 and 7 for epidemics in military populations
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Respiratory syncytial virus
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Lower respiratory illness (infants)
Mild upper respiratory illness (adults)
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Widespread in children
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Ribavirin sometimes used in immunocompromised patients
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Palivizumab IM† monthly
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Rhinoviruses
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Common cold
Acute coryza with or without fever
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Universal, especially during cold months
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None
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None
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* Nonspecific precautions (eg, avoidance of infected patients and insect and animal vectors, routine hygiene measures) are also recommended.
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†Unlike RSV-IVIG, palivizumab does not interfere with immunizations (eg, MMR, chickenpox).
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AFRD = acute febrile respiratory disease; MMR = measles, mumps, and rubella; RSV = respiratory syncytial virus; IVIG = IV immune globulin.
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GI infections
Gastroenteritis is usually caused by viruses (see Gastroenteritis) and transmitted from person-to person by the oral-fecal route. Age group primarily affected depends on the virus:
Local epidemics may occur in children, particularly during colder months.
The main symptoms are vomiting and diarrhea.
No specific treatment is recommended, but supportive care, particularly rehydration, is important.
A rotavirus vaccine that is effective against most pathogenic strains is part of the recommended infant vaccination schedule (see Table 12: Approach to the Care of Normal Infants and Children: Recommended Immunization Schedule for Ages 0–6 yr). Hand washing and good sanitation measures can help prevent spread.
Exanthematous infections
Some viruses cause only skin lesions (as in molluscum contagiosum and warts—See Viral Skin Diseases); others also cause systemic manifestations or lesions elsewhere in the body (see Table 2: Viruses: Some Exanthematous Viruses). Transmission is typically from person to person; alphaviruses have a mosquito vector.
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Table 2
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| Some Exanthematous Viruses |
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Principal Syndromes
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Prevalence and Distribution
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Specific Therapy
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Specific Prevention*
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Rubeola virus
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Measles
Encephalomyelitis
CNS involvement (rare)
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Global
Incidence decreasing because of vaccine
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None
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Vaccines
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Rubella virus
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German measles
Birth defects due to infection during pregnancy
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Universal
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None
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Vaccines
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Human parvovirus B19
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Erythema infectiosum (fifth disease)
Rash, malaise, arthritis
Hydrops fetalis (infection during pregnancy)
Anemia (in immunocompromised hosts or patients with hemoglobinopathies)
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Sporadic outbreaks
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IVIG (for severe anemia)
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None
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Human herpesvirus type 6
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Roseola infantum (exanthem subitum)
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Widespread
Affects young children
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None
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None
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Varicella-zoster virus
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Chickenpox
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Before vaccine, almost universal in children, occasionally in adults
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Acyclovir, famciclovir, valacyclovir
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Immune globulins, vaccine
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Zoster
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Common in adults, resulting from reactivation of latent virus
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Acyclovir, famciclovir, valacyclovir
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Vaccine
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Variola
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Smallpox
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Natural disease eradicated
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Cidofovir†
Smallpox vaccine up to 4 days after exposure
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Vaccine
Cidofovir†
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Alphaviruses (some)
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Chikungunya disease (acute febrile illness followed by more chronic polyarthritis)
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Transmitted by Aedes mosquitoes
Africa, Southeast Asia, India, Europe
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None
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None
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Mayaro disease (a dengue-like disease)
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Mosquito-borne
South America, Trinidad
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None
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None
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Molluscum contagiosum virus
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Molluscum contagiosum papules
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Genital (adults)
Exposed skin (children)
More severe (AIDS patients)
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Cryotherapy, curettage
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None
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*Nonspecific precautions (eg, avoidance of infected patients and insect and animal vectors, routine hygiene measures) are also recommended.
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†Based on animal studies.
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Hepatic infections
At least 5 specific viruses (hepatitis A, B, C, D, and E viruses) can cause hepatitis; each causes a specific type of hepatitis (see Table 3: Viruses: Viral Hepatitis and see Hepatitis). Hepatitis D virus can infect only when hepatitis B is present. Transmission is from person to person by contact with infected blood or body secretions or by the fecal-oral route for hepatitis A and E.
Other viruses can affect the liver as part of their disease process. Common examples are cytomegalovirus, Epstein-Barr virus, and yellow fever virus. Less common examples are echovirus, coxsackievirus, and herpes simplex, rubeola, rubella, and varicella viruses.
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Table 3
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| Viral Hepatitis |
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Principal Syndromes
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Prevalence and Distribution
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Specific Therapy
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Specific Prevention*
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Hepatitis A (acute)
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Widespread, often epidemic
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None
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γ-Globulin, vaccine
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Hepatitis B (acute and chronic)
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Widespread
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Interferon, other antivirals
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Screening for hepatitis B surface antigen
Vaccine, γ- or hyperimmune globulin
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Hepatitis C (acute and chronic)
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Widespread
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Interferon, ribavirin
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Screening for hepatitis C
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Hepatitis D (delta)
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Endemic pockets in several countries
Parenteral drug users at relatively high risk
Can infect only in the presence of hepatitis B infection
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Interferon
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None
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Hepatitis E
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Outbreaks
Developing world
Severe during pregnancy
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None
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Vaccine in development
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*Nonspecific precautions (eg, avoidance of body fluids of infected patients, aseptic precautions, routine hygiene measures) are also recommended.
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Neurologic infections
Most cases of encephalitis are caused by viruses (see Table 4: Viruses: Some Neurologic Viruses and Brain Infections). Many of these viruses are transmitted to humans by blood-eating arthropods, mainly mosquitoes and ticks (see Arboviridae, Arenaviridae, and Filoviridae); these viruses are called arboviruses (arthropod-borne viruses). For such infections, prevention includes avoiding mosquito and tick bites.
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Table 4
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| Some Neurologic Viruses |
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Principal Syndromes
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Prevalence and Distribution
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Specific Therapy
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Specific Prevention*
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Polioviruses
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Poliomyelitis (acute flaccid paralysis)
Aseptic meningitis
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Global
Incidence now low because of vaccine
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None
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Vaccines: Live (oral), killed (injected)
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Alphaviruses (some), mosquito-borne
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Western equine encephalitis
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North and South America
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None
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None
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Eastern equine encephalitis
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North and South America
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None
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Vaccine available to protect equines only
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Venezuelan equine encephalitis
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Gulf states to South America
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None
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Vaccine available for equines
Investigational vaccine used in laboratory workers at risk
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Flaviviruses (some), mosquito-borne
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Japanese encephalitis
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Southeast Asia, Japan, Korea, China, India, Philippines, eastern former Soviet Union
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None
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Vaccine
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Murray Valley encephalitis
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Australia, New Guinea
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None
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None
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St. Louis encephalitis
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North and South America
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None
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None
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West Nile virus encephalitis
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Africa, Middle East, southern France, former Soviet Union, India, Indonesia, US
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None
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Screening blood and blood products for the virus
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Flaviviruses (some), tick-borne
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Powassan encephalitis
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Canada, northeastern US
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None
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None
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Tick-borne encephalitis
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Eastern and Central Europe, Balkans, former Soviet Union
Outbreaks that coincide with periods of tick activity
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None
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Vaccine available in Europe and Russia
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Bunyaviruses (some), mosquito-borne
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California encephalitis and related types (eg, La Crosse encephalitis)
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Probably worldwide
Common in Midwestern and eastern US
Symptomatic infection primarily in children
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None
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None
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Arenaviruses (some)
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Lymphocytic choriomeningitis
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US, Europe, possibly elsewhere
Chief reservoir: House mouse
Primarily in adults during autumn and winter
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None
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None
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Rabies virus
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Rabies
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Worldwide
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None
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Vaccine
Postexposure rabies immune globulin
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*Nonspecific precautions (eg, avoidance of contaminated food and water and insect and animal vectors, routine hygiene measures) are also recommended.
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Hemorrhagic fevers
Certain viruses cause fever and a bleeding tendency (see Table 5: Viruses: Some Viruses That Cause Hemorrhagic Fever and Arboviridae, Arenaviridae, and Filoviridae). Transmission may involve mosquitoes, ticks, or contact with infected animals (eg, rodents, monkeys, bats) and people. Prevention involves avoiding the means of transmission.
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Table 5
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| Some Viruses That Cause Hemorrhagic Fever |
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Principal Syndromes
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Distribution
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Specific Therapy
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Specific Prevention*
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Flaviviruses (some)
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Omsk hemorrhagic fever
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Former Soviet Union (Siberia)
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None
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None
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Kyasanur Forest disease
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India
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None
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None
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Yellow fever
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Africa, Central and South America
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None
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Vaccine for travelers to endemic areas
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Dengue fever
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Tropics and subtropics, worldwide
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None
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None
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Bunyaviruses (some)
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Hemorrhagic fever with renal syndrome due to Hantaan, Puumala, Dobrava (Belgrade), or Seoul virus
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Northern Asia, Europe, southwestern US
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Ribavirin
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None
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Filoviruses (some)
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Marburg virus infection
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Africa
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None
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None
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Ebola virus infection
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Africa, Philippines
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None
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None
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Arenaviruses (some)
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Lassa fever
Bolivian hemorrhagic fever (due to Machupo virus)
Argentinian hemorrhagic fever (due to Junin virus)
Venezuelan hemorrhagic fever (due to Guanarito virus)
Brazilian hemorrhagic fever (due to Sabia virus)
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South America, Africa (only Lassa fever)
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Ribavirin
Convalescent plasma for all except Lassa fever
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Vaccine for Argentinian hemorrhagic fever under investigation
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Nairovirus
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Crimean-Congo hemorrhagic fever
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Former Soviet Union, western Pakistan, Africa, Asia, Middle East, Eastern Europe
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Ribavirin
Possibly convalescent plasma
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Vaccine available in Eastern Europe
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*Nonspecific precautions (eg, avoidance of the means of transmission, routine hygiene measures) are also recommended.
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Cutaneous or mucosal infections
Some viruses cause skin or mucosal lesions that recur and may become chronic (see Table 6: Viruses: Some Viruses That Cause Recurrent or Chronic Skin or Mucosal Lesions). Mucocutaneous infections are the most common type of herpes simplex virus infection (see Herpesviruses: Herpes Simplex Virus (HSV) Infections). Human papillomavirus causes warts (see Viral Skin Diseases: Warts and see Sexually Transmitted Diseases (STDs): Genital Warts); some subtypes cause cervical cancer (see Gynecologic Tumors: Cervical Cancer). Transmission is by person-to-person contact.
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Table 6
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| Some Viruses That Cause Recurrent or Chronic Skin or Mucosal Lesions |
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Principal Syndromes
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Prevalence
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Specific Therapy
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Specific Prevention*
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Herpes simplex virus
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Herpes labialis
Herpetic gingivostomatitis
Dermatitis
Keratoconjunctivitis
Encephalitis
Vulvovaginitis
Neonatal disseminated disease
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Labial: Recurrent, almost universal
Gingivostomatitis: Frequent in infants and children
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Acyclovir, famciclovir, valacyclovir, penciclovir
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Neonatal infection: Treatment of maternal infection; suppressive therapy beginning at 36 wk of gestation if patients have a history of recurrent HSV; cesarean delivery if lesions or prodromal symptoms are present at time of delivery
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Human papillomavirus
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Warts (verrucae)
Genital warts
Cervical cancer
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Universal
Common, often recurrent
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Cryotherapy, interferon (possibly for genital), podophyllin (genital), imiquimod
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Vaccine for the 4 subtypes of HPV most commonly associated with cervical cancers and genital warts
Condoms
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*Nonspecific precautions (eg, routine hygiene measures, safe-sex practices) are also recommended.
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Multisystem diseases
Enteroviruses, which include coxsackieviruses and echoviruses (see Enteroviruses), can cause various multisystem syndromes, as can cytomegaloviruses (see Table 7: Viruses: Some Viruses That Cause Multisystem Disease and Herpesviruses: Cytomegalovirus (CMV) Infection). Transmission is by the fecal-oral route.
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Table 7
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| Some Viruses That Cause Multisystem Disease |
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Principal Syndromes
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Distribution and Prevalence
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Specific Therapy
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Specific Prevention*
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Coxsackieviruses
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Herpangina
Epidemic pleurodynia
Aseptic meningitis
Meningoencephalitis
Neonatal sepsis
Myocarditis
Pericarditis
AFRD (children)
Paralysis
Fever and exanthem
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Varies with types
Most people infected
Increased during warm months in temperate climates and year round in tropics and in children
Person-to-person spread usually via the fecal-oral route
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None
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None
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Echoviruses† and high-numbered enteroviruses
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Aseptic meningitis
Fever and exanthem
Meningoencephalitis
Neonatal sepsis
Paralysis
Myocarditis
Pericarditis
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As for coxsackieviruses
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None
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None
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Cytomegalovirus
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Congenital defects (cytomegalic inclusion disease)
Hepatitis (cytomegalovirus mononucleosis)
In immunocompromised patients (including those with AIDS): Retinitis, GI disorders, CNS disorders, pneumonia
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Widespread
Congenital
Common among immunocompromised patients
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Ganciclovir, foscarnet, cidofovir, sometimes immune globulin (eg, in organ transplant recipients with pneumonia)
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Ganciclovir, foscarnet
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*Nonspecific precautions (eg, adequate sanitation, hand washing) are also recommended.
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†Echovirus types 10, 21, 22, and 28 have been reclassified; these numbers are no longer used. More recently described enteroviruses have been designated as types 68 to 72.
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AFRD = acute febrile respiratory disease.
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Nonspecific febrile illness
Some viruses cause nonspecific symptoms, including fever, malaise, headaches, and myalgia (see Table 8: Viruses: Some Viruses That Cause Nonspecific Acute Febrile Illness and Table 1: Arboviridae, Arenaviridae, and Filoviridae: Arbovirus, Arenavirus, and Filovirus Diseases). Transmission is usually by an insect or arthropod vector.
Rift Valley fever rarely progresses to ocular disorders, meningoencephalitis, or a hemorrhagic form (which has a 50% mortality rate).
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Table 8
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| Some Viruses That Cause Nonspecific Acute Febrile Illness |
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Principal Syndromes
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Distribution
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Specific Therapy*
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Specific Prevention†
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Colorado tick fever virus (coltivirus)
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Colorado tick fever, with leukopenia and thrombocytopenia
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Western US, Canada
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None
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None
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Phleboviruses (some)
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Phlebotomus (sandfly) fever
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Mediterranean basin, Balkans, Middle East, Pakistan, India, China, eastern Africa, Panama, Brazil
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None
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None
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Rift Valley fever
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Eastern Africa, Egypt
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None
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Vaccine for livestock
Human vaccine under investigation
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*Treatment is usually supportive.
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†Nonspecific precautions (eg, avoidance of the means of transmission, routine hygiene measures, screening of bone marrow used for transplantation) are also recommended.
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Last full review/revision December 2009 by Kenneth M. Kaye, MD
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