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Types of Viral Disorders

By

Laura D Kramer

, PhD, Wadsworth Center, New York State Department of Health

Last full review/revision Jun 2021| Content last modified Jun 2021
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Categorizing viral infections by the organ system most commonly affected (eg, lungs, gastrointestinal tract, skin, liver, central nervous system, 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

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The most common viral infections are probably upper respiratory infections. Respiratory infections Overview of Viral Respiratory Infections Viral infections commonly affect the upper or lower respiratory tract. Although respiratory infections can be classified by the causative virus (eg, influenza), they are generally classified... read more are more likely to cause severe symptoms in infants, the elderly, and patients with a lung or heart disorder.

Respiratory viruses include the epidemic influenza viruses Influenza Influenza is a viral respiratory infection causing fever, coryza, cough, headache, and malaise. Mortality is possible during seasonal epidemics, particularly among high-risk patients (eg, those... read more (A and B), H5N1 and H7N9 avian influenza A viruses Avian Influenza Avian influenza is caused by strains of influenza A that normally infect only wild birds and domestic poultry. Infections due to some of these strains have been detected in humans. Human-to-human... read more , parainfluenza viruses Parainfluenza Virus Infections Parainfluenza viruses include several closely related viruses that cause many respiratory illnesses varying from the common cold to an influenza-like syndrome or pneumonia; croup is the most... read more 1 through 4, adenoviruses Adenovirus Infections Infection with one of the many adenoviruses may be asymptomatic or result in specific syndromes, including mild respiratory infections, keratoconjunctivitis, gastroenteritis, cystitis, and primary... read more , respiratory syncytial virus A and B and human metapneumovirus Respiratory Syncytial Virus (RSV) and Human Metapneumovirus Infections Respiratory syncytial virus and human metapneumovirus infections cause seasonal lower respiratory tract disease, particularly in infants and young children. Disease may be asymptomatic, mild... read more , rhinoviruses Common Cold The common cold is an acute, usually afebrile, self-limited viral infection causing upper respiratory symptoms, such as rhinorrhea, cough, and sore throat. Diagnosis is clinical. Handwashing... read more , and coronaviruses Coronaviruses and Acute Respiratory Syndromes (COVID-19, MERS, and SARS) Coronaviruses are enveloped RNA viruses that cause respiratory illnesses of varying severity from the common cold to fatal pneumonia. Numerous coronaviruses, first discovered in domestic poultry... read more (see table Some Respiratory Viruses Some Respiratory Viruses Categorizing viral infections by the organ system most commonly affected (eg, lungs, gastrointestinal tract, skin, liver, central nervous system, mucous membranes) can be clinically useful,... read more ).

Several coronaviruses cause a respiratory infection that can be severe. In 2002 and 2003, an outbreak of severe acute respiratory syndrome Severe Acute Respiratory Syndrome (SARS) Coronaviruses are enveloped RNA viruses that cause respiratory illnesses of varying severity from the common cold to fatal pneumonia. Numerous coronaviruses, first discovered in domestic poultry... read more (SARS) caused a number of deaths mostly in China and Hong Kong. There have been no cases of SARS reported since 2004. In 2012, a novel coronavirus Middle East respiratory syndrome coronavirus Middle East Respiratory Syndrome (MERS) Coronaviruses are enveloped RNA viruses that cause respiratory illnesses of varying severity from the common cold to fatal pneumonia. Numerous coronaviruses, first discovered in domestic poultry... read more (MERS-CoV) appeared in Saudi Arabia; it can cause severe acute respiratory illness and is sometimes fatal (case fatality rate of 34%). In 2019, another coronavirus (SARS-CoV2) that can cause an acute, sometimes fatal respiratory illness (COVID-19 COVID-19 Coronaviruses are enveloped RNA viruses that cause respiratory illnesses of varying severity from the common cold to fatal pneumonia. Numerous coronaviruses, first discovered in domestic poultry... read more ) emerged in Wuhan, China and has spread in a worldwide pandemic that has killed millions (1 Reference Categorizing viral infections by the organ system most commonly affected (eg, lungs, gastrointestinal tract, skin, liver, central nervous system, mucous membranes) can be clinically useful,... read more ).

Respiratory viruses are typically spread from person to person by contact with infected respiratory droplets.

Gastrointestinal infections

Age group primarily affected depends on the virus:

  • Rotavirus: Children

  • Norovirus: Children and adults

  • Astrovirus: Usually infants and young children

  • Adenovirus 40 and 41: Infants

  • Coronavirus-like agents: Infants

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.

Exanthematous infections

Hepatic infections

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At least 5 specific viruses (hepatitis A, B, C, D, and E viruses) can cause hepatitis Causes of Hepatitis Hepatitis is an inflammation of the liver characterized by diffuse or patchy necrosis. Hepatitis may be acute or chronic (usually defined as lasting > 6 months). Most cases of acute viral hepatitis... read more ; each causes a specific type of 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 (genotypes 1 and 2).

Other viruses can affect the liver as part of their disease process. Common examples are cytomegalovirus Cytomegalovirus (CMV) Infection Cytomegalovirus (CMV, human herpesvirus type 5) can cause infections that have a wide range of severity. A syndrome of infectious mononucleosis that lacks severe pharyngitis is common. Severe... read more , Epstein-Barr virus Infectious Mononucleosis Infectious mononucleosis is caused by Epstein-Barr virus (EBV, human herpesvirus type 4) and is characterized by fatigue, fever, pharyngitis, and lymphadenopathy. Fatigue may persist weeks or... read more Infectious Mononucleosis , and yellow fever Yellow Fever Yellow fever is a mosquito-borne flavivirus infection endemic in tropical South America and sub-Saharan Africa. Symptoms may include sudden onset of fever, relative bradycardia, headache, and... read more virus. Less common examples are echovirus, coxsackievirus, and herpes simplex Herpes Simplex Virus (HSV) Infections Herpes simplex viruses (human herpesviruses types 1 and 2) commonly cause recurrent infection affecting the skin, mouth, lips, eyes, and genitals. Common severe infections include encephalitis... read more Herpes Simplex Virus (HSV) Infections , rubeola, rubella Measles, Mumps, and Rubella (MMR) Vaccine The measles, mumps, and rubella (MMR) vaccine effectively protects against all 3 infections. People who are given the MMR vaccine according to the US vaccination schedule are considered protected... read more , and varicella Chickenpox Chickenpox is an acute, systemic, usually childhood infection caused by the varicella-zoster virus (human herpesvirus type 3). It usually begins with mild constitutional symptoms that are followed... read more Chickenpox viruses.

Neurologic infections

Hemorrhagic fevers

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Certain viruses cause fever and a bleeding tendency. (See also Arbovirus, Arenavirus, and Filovirus Infections .)

Transmission may involve mosquitoes, ticks, or contact with infected animals (eg, rodents, monkeys, bats) and people. Prevention involves avoiding the means of transmission.

Cutaneous or mucosal infections

Multisystem diseases

Nonspecific febrile illness

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Some viruses cause nonspecific symptoms, including fever, malaise, headaches, and myalgia. Transmission is usually by an arthropod vector. (See also Arbovirus, Arenavirus, and Filovirus Infections .)

Rift Valley fever rarely progresses to ocular disorders, meningoencephalitis, or a hemorrhagic form (which has a 50% mortality rate).

Reference

  • 1. Mahase E: Coronavirus covid-19 has killed more people than SARS and MERS combined, despite lower case fatality rate. BMJ 368:m641, 2020. doi: 10.1136/bmj.m641 PMID: 32071063.

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