Topic
Viral Syndromes by Organ System
Viral disease organised by the organ system it strikes: the gut, the heart, the skin, the genital and urinary tract, and the eye. Each article is a syndromic overview of the viruses that target that system, the clinical approach to them, and how they are told apart; the individual agents are covered in depth in their own profiles.
Most of clinical virology can be entered two ways: through the virus or through the organ it damages. The virus profiles take the first route. This topic takes the second, grouping viral disease by the system it strikes, because that is how patients present. A child with watery diarrhoea, an adult with pericarditic chest pain, a widespread rash, a genital ulcer or a red painful eye each defines a syndrome first, and the differential of viral causes follows from the site.
Two ideas run through every article here. The first is that a single organ syndrome usually has several viral causes that cannot be told apart clinically, so the approach is a structured differential rather than pattern recognition of one agent. The second is the division of labour with the virus profiles: these articles cover the syndrome, its pathogenesis at the tissue level, the diagnostic and management approach, and the comparative “which virus does what” of each system, while the structure, replication and molecular detail of each agent live in its own profile.
Explore the syndromes
→ See Gastrointestinal Viral Infections for the diarrhoea-and-vomiting viruses (rotavirus, norovirus, sapovirus, astrovirus and the enteric adenoviruses), the endemic-versus-outbreak patterns, and the assessment of the dehydrated child.
→ See Viral Cardiac Infections for viral myocarditis and pericarditis: the enteroviruses and other agents, the two-phase pathogenesis, and the difficult diagnosis and supportive management.
→ See Viral Exanthems for the skin rashes, grouped by morphology, with the classic childhood exanthems (measles, rubella, erythema infectiosum, roseola), varicella and the poxviruses.
→ See Viral Genitourinary Infections for the organ-tropic infections (genital herpes, anogenital HPV, urinary-tract viruses) and their distinction from the systemic viruses that are merely sexually transmitted.
→ See Viral Diseases of the Eye for the ocular syndromes (conjunctivitis, keratitis, uveitis, retinitis) and their viral causes, from adenoviral conjunctivitis to CMV retinitis.
Related organ-system reviews
Two other organ systems are reviewed the same way but carry enough weight to stand as topics in their own right.
→ See Viral Diseases of the Central Nervous System for meningitis, encephalitis and myelitis and their viral causes.
→ See Viral Respiratory Infections: an Overview for the syndromes from the common cold down to pneumonia.
The syndromes at a glance
Each organ system has a characteristic set of viral causes and a hallmark presentation.
| Organ system | Key viruses | Hallmark |
|---|---|---|
| Gastrointestinal | Rotavirus, norovirus, sapovirus, astrovirus, enteric adenovirus 40/41 | Watery diarrhoea and vomiting; death by dehydration |
| Heart | Coxsackievirus B and other enteroviruses, adenovirus, parvovirus B19 | Myocarditis and pericarditis |
| Skin | Measles, rubella, parvovirus B19, HHV-6 and HHV-7, VZV, enteroviruses, poxviruses | Maculopapular, vesicular and nodular rashes |
| Genitourinary | HSV, HPV, BK polyomavirus, adenovirus (and HIV, HBV and others as sexually transmitted) | Genital ulcers and warts; cystitis and nephropathy |
| Eye | HSV, VZV, adenovirus, CMV, enterovirus 70 and coxsackievirus A24 | Keratitis, conjunctivitis and retinitis |
HHV-6 and HHV-7 are human herpesviruses 6 and 7, VZV varicella-zoster virus, HSV herpes simplex virus, HPV human papillomavirus, CMV cytomegalovirus, HIV human immunodeficiency virus and HBV hepatitis B virus.
The gastrointestinal tract
Viral gastroenteritis is a diarrhoea-and-vomiting illness dominated in early childhood by rotavirus, with norovirus, sapovirus, astrovirus and the enteric adenoviruses completing the group. The agents cannot be told apart clinically, and the illness runs in two epidemiological patterns: endemic childhood disease and explosive outbreaks, the latter driven mainly by norovirus. The illness is self-limited but kills through dehydration, so the clinical priority is assessing and correcting fluid loss, and rotavirus vaccination is the one effective preventive intervention.
The heart
Viruses are the commonest cause of myocarditis, an inflammatory infiltrate of the heart muscle with death of adjacent myocytes, and of the pericarditis that often accompanies it. The classical agents are the enteroviruses, above all coxsackievirus B, together with the adenoviruses and parvovirus B19. Injury is caused first by the virus and then by the immune response, the illness ranges from a trivial subclinical infection to fulminant heart failure, and a proportion of cases progress to dilated cardiomyopathy. Diagnosis is difficult, and management is supportive.
The skin
Viral rashes (exanthems) accompany systemic infection, with an enanthem the mucosal counterpart. They are grouped by the morphology of the lesion into maculopapular, vesicular, vesiculopustular and nodular, and the rash is rarely diagnostic on its own. The core is the classic childhood exanthems, measles, rubella, erythema infectiosum and roseola, alongside varicella and the poxviruses. Most are self-limited; the priorities are recognising measles and its complications, treating varicella and zoster, and preventing the vaccine-preventable rashes.
The genitourinary tract
Viruses involve the genitourinary tract two ways that must be kept separate. A few have tropism for the genital and urinary organs and cause disease there: genital herpes, anogenital warts and their cancers, and urinary-tract infections such as adenoviral haemorrhagic cystitis and BK polyomavirus nephropathy. Separately, many important systemic viruses, HIV foremost among them, are sexually transmitted or shed in genital secretions but cause no genital-tract disease. The organ-tropic infections are the focus; the systemic viruses are covered under their own topics.
The eye
Viruses cause disease across every ocular structure, described as clinical syndromes (conjunctivitis, keratitis, scleritis, uveitis, retinitis and adnexal disease) or by pathogen. Herpes simplex keratitis is a leading infectious cause of corneal blindness, cytomegalovirus retinitis is an AIDS-defining illness, adenovirus is the commonest cause of viral conjunctivitis, and measles is the commonest cause of childhood blindness in low-income settings. The eye is immune-privileged, which both limits defence and means the immune response itself can threaten sight.
References and recommended reading
- Richman DD, Whitley RJ, Hayden FG, editors. Clinical Virology, 4th edition. Washington: ASM Press; 2016. The syndrome chapters underpinning each article in this topic.
- Burrell CJ, Howard CR, Murphy FA. Fenner and White’s Medical Virology, 5th edition. Academic Press / Elsevier; 2017. The source for the cross-cutting organ-system syndrome overviews.