Viral pneumonia

Short description: Disease

Viral pneumonia

Specialty| Infectious disease, respirology
Influenza pneumonia

Viral pneumonia is a pneumonia caused by a virus. Pneumonia is an infection that causes inflammation in one or both lungs. The pulmonary alveoli fill with fluid or pus making it difficult to breathe.[1] Pneumonia can be caused by bacteria, viruses, fungi or parasites.[1] Viruses are the most common cause of pneumonia in children, while in adults bacteria are a more common cause.[2]

## Contents

* 1 Signs and symptoms
* 2 Diagnosis
* 3 Cause
* 4 History
* 5 Pathophysiology
* 6 Prevention
* 7 Treatment
* 8 Epidemiology
* 9 References
* 10 External links

## Signs and symptoms

Symptoms of viral pneumonia include fever, productive cough, runny nose, chest pain and systemic symptoms (e.g. myalgia, headache). Different viruses cause different symptoms.

## Diagnosis

Diagnosis, like with any infection, relies on the detection of the infectious cause. With viral pneumonia, samples are taken from the upper and/or lower respiratory tracts.[3] The samples can then be run through polymerase chain reaction (PCR), allowing for amplification of the virus as that allows better detection if present in the sample.[4] Other ways for a diagnosis to be obtained is by ordering a chest X-ray, blood tests, pulse oximetry, and a medical/family history to see if there are any known risks or previous exposures to a person with viral pneumonia.[4] If the person is in serious condition and in the hospital there are more invasive studies that can be run to diagnose the person.[4]

## Cause

Common causes of viral pneumonia are:

* Influenza virus A and B[5]
* Respiratory syncytial virus (RSV)[5]
* Human parainfluenza viruses (in children)[5]
* Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)[6]

Rarer viruses that commonly result in pneumonia include:

* Adenoviruses (in military recruits)[5]
* Metapneumovirus[7]
* Severe acute respiratory syndrome coronavirus (SARS-CoV)[8]
* Middle East respiratory syndrome virus (MERS-CoV)
* Hantaviruses[9]

Viruses that primarily cause other diseases, but sometimes cause pneumonia include:

* Herpes simplex virus (HSV), mainly in newborns or young children
* Varicella-zoster virus (VZV)
* Measles virus
* Rubella virus
* Cytomegalovirus (CMV), mainly in people with immune system problems
* Smallpox virus
* Dengue virus

The most commonly identified agents in children are respiratory syncytial virus, rhinovirus, human metapneumovirus, human bocavirus, and parainfluenza viruses.[7]

## History

In the pre-antibiotic age, pneumonias had been treated with specific anti-serums of highly variable therapeutic effect and undesirable side-effects (a practice eliminated by the advent of sulfamides in 1936 and the beginning availability of penicillin in the 1940s).

Viral pneumonia was first described by Hobart Reimann in 1984, in an article published by JAMA, An Acute Infection of the Respiratory Tract with Atypical Pneumonia: a disease entity probably caused by a filtrable virus. Reimann, Chairman of the Department of Medicine at Jefferson Medical College, had established the practice of routinely typing the pneumococcal organism in cases where pneumonia presented. Out of this work, the distinction between viral and bacterial strains was noticed.[10]

## Pathophysiology

Viruses must invade cells in order to reproduce. Typically, a virus will reach the lungs by traveling in droplets through the mouth and nose with inhalation. There, the virus invades the cells lining the airways and the alveoli. This invasion often leads to cell death either through direct killing by the virus or by self-destruction through apoptosis.

Further damage to the lungs occurs when the immune system responds to the infection. White blood cells, in particular lymphocytes, are responsible for activating a variety of chemicals (cytokines) which cause leaking of fluid into the alveoli. The combination of cellular destruction and fluid-filled alveoli interrupts the transportation of oxygen into the bloodstream.

In addition to the effects on the lungs, many viruses affect other organs and can lead to illness affecting many different bodily functions. Some viruses also make the body more susceptible to bacterial infection; for this reason, bacterial pneumonia often complicates viral pneumonia.

## Prevention

The best prevention against viral pneumonia is vaccination against influenza, chickenpox (varicella zoster), herpes zoster, measles, respiratory syncytial virus vaccine (RSV), rubella, and adenovirus vaccine.[11][12] Besides vaccination there are no other ways to prevent viral pneumonia besides basic hygiene skills like covering the mouth when coughing or sneezing, staying home when sick, and washing your hands frequently.

## Treatment

In cases of viral pneumonia where influenza A or B are thought to be causative agents, patients who are seen within 48 hours of symptom onset may benefit from treatment with baloxavir, oseltamivir, or zanamivir, or peramivir.[13] Baloxavir can be combined with e.g. oseltamivir, because they have different mechanisms of action and are synergistic. Respiratory syncytial virus (RSV) has no direct acting treatments, but ribavirin is indicated for severe cases.[13] Ribavirin has also been known to be used as a treatment for parainfluenza virus, and adenovirus.[13] Herpes simplex virus and varicella-zoster virus infections are usually treated with acyclovir, whilst ganciclovir is used to treat cytomegalovirus.[13] There is no known efficacious treatment for pneumonia caused by SARS coronavirus, MERS coronavirus, or hantavirus. Other forms of care are largely supportive like oxygen supplementation, treatment of comorbidities, and controlling other symptoms, fever and cough, with medications.[13]

## Epidemiology

There are roughly 450 million cases of pneumonia every year. Of those case, viral pneumonia counts for about 200 million cases which includes about 100 million children and 100 million adults.[14] Viral pneumonia is more prevalent in the very young, less than 5 years old, and in the very old, more than 75 years old.[14] Developing countries have a higher rate of incidence when it comes to viral pneumonia. On average, developing countries have an incidence rate five times higher than that of developed countries.[14] Being pregnant can also affect the chances of developing viral pneumonia.[15] As with all infectious diseases, viral pneumonia preys on the immunocompromised as well as individuals with one or more comorbidities especially those with:

* Trauma[15]
* Severe burns[15]
* Diabetes[15]
* Malnutrition[15]
* Poverty[15]
* Environmental Exposure[15]
* Group living[15]

## References

1. ↑ 1.0 1.1 "Pneumonia | NHLBI, NIH". https://www.nhlbi.nih.gov/health/pneumonia.
2. ↑ Ruuskanen, Olli; Lahti, Elina; Jennings, Lance C; Murdoch, David R (2011-04-09). "Viral pneumonia" (in en). The Lancet 377 (9773): 1264–1275. doi:10.1016/S0140-6736(10)61459-6. ISSN 0140-6736. PMID 21435708.
3. ↑ Ruuskanen, Olli; Lahti, Elina; Jennings, Lance C; Murdoch, David R (2011-04-09). "Viral pneumonia" (in en). The Lancet 377 (9773): 1264–1275. doi:10.1016/S0140-6736(10)61459-6. ISSN 0140-6736. PMID 21435708.
4. ↑ 4.0 4.1 4.2 "Pneumonia | NHLBI, NIH". https://www.nhlbi.nih.gov/health/pneumonia.
5. ↑ 5.0 5.1 5.2 5.3 Table 13-7 in: Mitchell, Richard Sheppard; Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson (2007). Robbins Basic Pathology: With STUDENT CONSULT Online Access. Philadelphia: Saunders. ISBN 978-1-4160-2973-1. 8th edition.
6. ↑ Huang, Chaolin; Wang, Yeming; Li, Xingwang; Ren, Lili; Zhao, Jianping; Hu, Yi; Zhang, Li; Fan, Guohui et al. (15 February 2020). "Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China". The Lancet 395 (10223): 497–506. doi:10.1016/S0140-6736(20)30183-5. PMID 31986264.
7. ↑ 7.0 7.1 Ruuskanen, O; Lahti, E; Jennings, LC; Murdoch, DR (2011-04-09). "Viral pneumonia.". Lancet 377 (9773): 1264–75. doi:10.1016/S0140-6736(10)61459-6. PMID 21435708.
8. ↑ "SARS Basics Fact Sheet". 6 December 2017. https://www.cdc.gov/sars/about/fs-sars.html.
9. ↑ Colby, Thomas V.; Zaki, Sherif R.; Feddersen, Richard M.; Nolte, Kurt B. (October 2000). "Hantavirus Pulmonary Syndrome Is Distinguishable From Acute Interstitial Pneumonia". Archives of Pathology & Laboratory Medicine 124 (10): 1463–1466. doi:10.5858/2000-124-1463-HPSIDF. PMID 11035576. https://www.archivesofpathology.org/doi/full/10.1043/0003-9985(2000)124<1463:HPSIDF>2.0.CO;2.
10. ↑ John H, Hodges MD (1989). "Thomas Jefferson University: Tradition and Heritage". in Wagner, MD, Frederick B. p. 253. https://jdc.jefferson.edu/cgi/viewcontent.cgi?article=1009&context=wagner2.
11. ↑ Ruuskanen, Olli; Lahti, Elina; Jennings, Lance C; Murdoch, David R (2011-04-09). "Viral pneumonia" (in en). The Lancet 377 (9773): 1264–1275. doi:10.1016/S0140-6736(10)61459-6. ISSN 0140-6736. PMID 21435708.
12. ↑ Freeman, Andrew M.; Leigh, Jr (2020), "Viral Pneumonia", StatPearls (Treasure Island (FL): StatPearls Publishing), PMID 30020658, https://www.ncbi.nlm.nih.gov/books/NBK513286/, retrieved 2020-11-11
13. ↑ 13.0 13.1 13.2 13.3 13.4 Freeman, Andrew M.; Leigh, Jr (2020), "Viral Pneumonia", StatPearls (Treasure Island (FL): StatPearls Publishing), PMID 30020658, https://www.ncbi.nlm.nih.gov/books/NBK513286/, retrieved 2020-11-11
14. ↑ 14.0 14.1 14.2 Ruuskanen, Olli; Lahti, Elina; Jennings, Lance C; Murdoch, David R (2011-04-09). "Viral pneumonia" (in en). The Lancet 377 (9773): 1264–1275. doi:10.1016/S0140-6736(10)61459-6. ISSN 0140-6736. PMID 21435708.
15. ↑ 15.0 15.1 15.2 15.3 15.4 15.5 15.6 15.7 Freeman, Andrew M.; Leigh, Jr (2020), "Viral Pneumonia", StatPearls (Treasure Island (FL): StatPearls Publishing), PMID 30020658, https://www.ncbi.nlm.nih.gov/books/NBK513286/, retrieved 2020-11-11

## External links

Classification|

* ICD-10: J12
* ICD-9-CM: 480
* MeSH: D011024
* SNOMED CT: 75570004

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External resources|

* MedlinePlus: 000073
* eMedicine: emerg/468 radio/539

* v
* t
* e

Diseases of the respiratory system (J, 460–519)

Upper RT
(including URTIs,
common cold)|

| Head|

sinuses

Sinusitis

nose

Rhinitis

Vasomotor rhinitis
Atrophic rhinitis
Hay fever
Nasal polyp
Rhinorrhea
nasal septum

Nasal septum deviation
Nasal septum perforation
Nasal septal hematoma

tonsil

Tonsillitis
Adenoid hypertrophy
Peritonsillar abscess

|

Neck|

pharynx

Pharyngitis

Strep throat
Laryngopharyngeal reflux (LPR)
Retropharyngeal abscess

larynx

Croup
Laryngomalacia
Laryngeal cyst
Laryngitis
Laryngopharyngeal reflux (LPR)
Laryngospasm

vocal cords

Laryngopharyngeal reflux (LPR)
Vocal fold nodule
Vocal fold paresis
Vocal cord dysfunction

epiglottis

Epiglottitis

trachea

Tracheitis
Laryngotracheal stenosis

Lower RT/lung disease
(including LRTIs)|

| Bronchial/
obstructive|

acute

Acute bronchitis

chronic

COPD

Chronic bronchitis
Acute exacerbation of COPD)
Asthma (Status asthmaticus
Aspirin-induced
Exercise-induced
Bronchiectasis

unspecified

Bronchitis
Bronchiolitis

Bronchiolitis obliterans
Diffuse panbronchiolitis

|

Interstitial/
restrictive
(fibrosis)|

| External agents/
occupational
lung disease|

Pneumoconiosis

Aluminosis
Asbestosis
Baritosis
Bauxite fibrosis
Berylliosis
Caplan's syndrome
Chalicosis
Coalworker's pneumoconiosis
Siderosis
Silicosis
Talcosis
Byssinosis

Hypersensitivity pneumonitis

Bagassosis
Bird fancier's lung
Farmer's lung
Lycoperdonosis

|

Other|

* ARDS
* Combined pulmonary fibrosis and emphysema
* Pulmonary edema
* Löffler's syndrome/Eosinophilic pneumonia
* Respiratory hypersensitivity
* Allergic bronchopulmonary aspergillosis
* Hamman-Rich syndrome
* Idiopathic pulmonary fibrosis
* Sarcoidosis
* Vaping-associated pulmonary injury

Obstructive or
restrictive|

| Pneumonia/
pneumonitis|

| By pathogen|

* Viral
* Bacterial
* Pneumococcal
* Klebsiella
* Atypical bacterial
* Mycoplasma
* Legionnaires' disease
* Chlamydiae
* Fungal
* Pneumocystis
* Parasitic
* noninfectious
* Chemical/Mendelson's syndrome
* Aspiration/Lipid

|

By vector/route|

* Community-acquired
* Healthcare-associated
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By distribution|

* Broncho-
* Lobar

IIP|

* UIP
* DIP
* BOOP-COP
* NSIP
* RB

Other|

* Atelectasis
* circulatory
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* Pulmonary embolism
* Lung abscess

Pleural cavity/
mediastinum|

| Pleural disease|

* Pleuritis/pleurisy

* [[Medicine:PneumoPneumothorax]]/Hemopneumothorax

Pleural effusion

Hemothorax
Hydrothorax
Chylothorax
Empyema/pyothorax
Malignant

Fibrothorax

|

Mediastinal disease|

* Mediastinitis
* Mediastinal emphysema

Other/general|

* Respiratory failure
* Influenza
* SARS
* Coronavirus disease 2019
* Idiopathic pulmonary haemosiderosis
* Pulmonary alveolar proteinosis

* v
* t
* e

Infectious diseases – viral systemic diseases (A80–B34, 042–079)

Oncovirus|

DNA virus
HBV

Hepatocellular carcinoma
HPV

Cervical cancer
Anal cancer
Penile cancer
Vulvar cancer
Vaginal cancer
Oropharyngeal cancer
KSHV

Kaposi's sarcoma
EBV

Nasopharyngeal carcinoma
Burkitt's lymphoma
Hodgkin's lymphoma
Follicular dendritic cell sarcoma
Extranodal NK/T-cell lymphoma, nasal type
MCPyV

Merkel-cell carcinoma

RNA virus
HCV

Hepatocellular carcinoma
Splenic marginal zone lymphoma
HTLV-I

Adult T-cell leukemia/lymphoma

Immune disorders|

* HIV
* AIDS

Central
nervous system|

| Encephalitis/
meningitis|

DNA virus
Human polyomavirus 2

Progressive multifocal leukoencephalopathy

RNA virus
MeV

Subacute sclerosing panencephalitis
LCV

Lymphocytic choriomeningitis
Arbovirus encephalitis
Orthomyxoviridae (probable)

Encephalitis lethargica

Rabies
Chandipura vesiculovirus
Herpesviral meningitis
Ramsay Hunt syndrome type 2

|

Myelitis|

* Poliovirus
* Poliomyelitis
* Post-polio syndrome
* HTLV-I
* Tropical spastic paraparesis

Eye|

* Cytomegalovirus
* Cytomegalovirus retinitis
* HSV
* Herpes of the eye

Cardiovascular|

* CBV
* Pericarditis
* Myocarditis

Respiratory system/
acute viral nasopharyngitis/
viral pneumonia|

| DNA virus|

* Epstein–Barr virus
* EBV infection/Infectious mononucleosis
* Cytomegalovirus

|

RNA virus|

* IV: SARS coronavirus
* Severe acute respiratory syndrome
* MERS coronavirus
* Middle East respiratory syndrome
* SARS coronavirus 2
* Coronavirus disease 2019

* V: Orthomyxoviridae: Influenza virus A/B/C/D
* Influenza/Avian influenza

* V, Paramyxoviridae: Human parainfluenza viruses
* Parainfluenza
* Human orthopneumovirus
* hMPV

Human digestive system|

| Pharynx/Esophagus|

* MuV
* Mumps
* Cytomegalovirus
* Cytomegalovirus esophagitis

|

Gastroenteritis/
diarrhea|

DNA virus
Adenovirus

Adenovirus infection

RNA virus
Rotavirus
Norovirus
Astrovirus
Coronavirus

Hepatitis|

DNA virus
HBV (B)

RNA virus
CBV
HAV (A)
HCV (C)
HDV (D)
HEV (E)
HGV (G)

Pancreatitis|

* CBV

Urogenital|

* BK virus
* MuV
* Mumps

* v
* t
* e

Pneumonia

Infectious pneumonias|

* Bacterial pneumonia
* Viral pneumonia
* Fungal pneumonia
* Parasitic pneumonia
* Atypical pneumonia
* Community-acquired pneumonia
* Healthcare-associated pneumonia
* Hospital-acquired pneumonia
* Ventilator-associated pneumonia
* Severe acute respiratory syndrome

Pneumonias caused by
infectious or noninfectious agents|

* Aspiration pneumonia
* Lipid pneumonia
* Eosinophilic pneumonia
* Bronchiolitis obliterans organizing pneumonia

Noninfectious pneumonia|

* Chemical pneumonitis
* Idiopathic pneumonia syndrome

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