Notes
Viral Respiratory Infections
Sections
Overview
Many viruses can cause multiple illnesses; the type and degree of illness often depends on host factors, including immune status and age.
Respiratory viruses often have systemic effects. Although they primarily target respiratory tissues, these effects are due to inflammation, impairment of lung function, etc.
Upper respiratory infections, specifically, are the most common infectious disease; though often self-limiting, they can have serious complications and may progress to involve the lower respiratory tract.
Respiratory viruses are transmitted in respiratory droplets, aerosols, saliva, and via the hands and other hard surfaces.
Nasal and oral cavities are continuous with the pharynx.
Trachea leads to the bronchial tree.
Paranasal sinuses are spaces within the skull; they can become inflamed and sore.
Upper Respiratory Tract Infections
Common Cold
Viruses:
Rhinovirus accounts for most cases of the cold, followed by Coronavirus, Adenovirus, Respiratory syncytial virus (referred to as RSV from here on), Parainfluenza virus, and Human metapneumovirus.
These viruses invade the respiratory epithelial tissue and trigger inflammation, which produces redness and edema.
Signs and Symptoms:
Individuals with the cold typically have the following symptoms:
– Congested and/or runny nose, cough, and sore throat.
– Aches and pains are possible.
The common cold is self-limiting, and lasts approximately 7 to 10 days.
Fever is rare, but complications, such as sinusitis and pneumonia, can occur; complications are more likely in the elderly and others with immune deficiencies.
Pharyngitis (Sore Throat)
Viruses:
Caused by adenovirus and herpes simplex virus. It is also associated cold and flu viruses.
Signs and Symptoms:
Pharyngitis is characterized by infected and inflamed tonsils, which produces a scratchy throat and, possibly, difficulty swallowing.
Herpangina
Caused by Coxasackievirus A; it is characterized by small whitish patches spread over the upper palate and throat.
This infection is most common in children.
Infections of both Upper & Lower Respiratory Tracts
Laryngotracheobronchitis (Croup)
Viruses:
Most often attributed to Parainfluenza virus, type 1, followed by RSV and Adenovirus; Influenza A and B viruses can also cause croup.
Signs and Symptoms:
Affected adults are likely to experience hoarseness.
Children are more often affected, particularly between the ages of 6 months to three years; croup is a common infection in this age group.
Croup in small children is characterized by inspiratory stridor, which produces a "squeak"-like sound, and/or tachypnea, which is often referred to as a "seal bark" cough; these are the result of swelling in the trachea, larynx, and bronchi.
X-rays often show a "steeple sign" (sometimes called "wine bottle" sign), caused by subglottic narrowing of the trachea.
Influenza
Viruses:
Caused by Influenza viruses A and B;
Signs and Symptoms:
Patients experience aches and chills, with possible fever, as well as fatigue, respiratory symptoms (cough, sinus congestion), sore throat, and, especially in children, vomiting and diarrhea.
Complications, including sinusitis, pneumonia, and inflammation of key organ systems, can occur.
Lower Respiratory Tract Infections
Bronchiolitis
Most common in children under two years of age.
Viruses:
Most often caused by RSV, though rhinovirus and parainfluenza virus can also cause bronchiolitis.
Bronchiolitis occurs when the small bronchial tubes become inflamed, necrotic, and, subsequently, narrowed by mucus and debris.
As a result, some alveoli collapse because air cannot be delivered to them, whereas low-oxygen air is trapped in other alveoli.
Signs and Symptoms:
Infants can experience fever, congestion or runny nose, coughing, and wheezing. Cyanosis, particularly of the lips and nail beds, can occur as the result of reduced oxygen levels.
Other signs of bronchiolitis include: rapid, shallow breathing and/or apnea, with wheezing and crackling.
Infants struggling to breath may grunt and, as a result of accessory muscle involvement, retractions may be observed – look for "sucking in" of the skin around the base of the neck as the infant struggles to bring in air.
Due to congestion and obstructed breathing, infants may also have difficulty bringing in foods and liquids, which can lead to dehydration.
Pneumonia
Infection and inflammation of the lung parenchyma.
Viruses:
Be aware that, due to antibacterial vaccines and other factors, viral causes of pneumonia are increasingly common.
Children: RSV is a significant cause of viral pneumonia in children, followed by parainfluenza and influenza viruses.
Adults: Influenza viruses are the most significant cause of viral pneumonia in adults, followed by RSV, parainfluenza viruses, adenovirus, and rhinovirus (rhinovirus-induced pneumonia is most common in elderly and/or immunocompromised individuals).
Signs and Symptoms:
Patients may experience fever, chills, and aches, as well as chest pains, shortness of breath, and rapid heart rate; sputum is often yellow or green from mucus, or even red, from blood.
Vomiting and diarrhea are possible, as is confusion.
Clinical Cases
Case 1: "Barky" seal-like cough
A 2-year-old girl was brought to the emergency department by her parents after a weekend trip to visit family. Her parents are concerned that she seems to have difficulty breathing for the past 12 hours. The patient developed rhinorrhea, nasal congestion, and a dry cough resembling a barking sound 3 days ago. She is up to date on her vaccinations; however, her mother stated that her side of the family does not believe in vaccinations and noted that the patient spent a substantial time playing with her cousins the whole weekend.
On examination, the patient's temperature is 99.8°F, blood pressure 92/64 mm Hg, heart rate 122/min, respiratory rate 30/min, SaO2 is 99 % on room air. Inspiratory stridor is heard when she cries.
What is the best next step in management?
Answer
- Dexamethasone
Explanation
Croup is a viral infection that produces laryngeal and tracheal inflammation, resulting in subglottic edema and narrowing of the airways. The typical presentation includes a "barky" seal-like cough with strider. In cases where the croup is mild and no inspiratory stridor is present at rest, treatment with a corticosteroid such as dexamethasone is necessary to reduce airway edema. Patients with moderate to severe croup such as respiratory discomfort and strider at rest should be treated with corticosteroids and nebulized epinephrine. Epinephrine will cause constriction of the mucosal arterioles in the upper airway and changes in capillary hydrostatic pressure, resulting in decreased airway edema and secretions.
Board Review
Common Cold
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USMLE & COMLEX-USA
Nurse Practitioner (NP)
Physician Assistant (PA)
Internal Medicine (ABIM)
Pharyngitis
USMLE & COMLEX-USA
Nurse Practitioner (NP)
Physician Assistant (PA)
Internal Medicine (ABIM)
Croup
Getting ready for boards? Review these concise, bulleted high yield reviews for your exam.
USMLE & COMLEX-USA
Nurse Practitioner (NP)
Physician Assistant (PA)
Internal Medicine (ABIM)
Influenza
Getting ready for boards? Review these concise, bulleted high yield reviews for your exam.
USMLE & COMLEX-USA
Nurse Practitioner (NP)
Physician Assistant (PA)
Internal Medicine (ABIM)
COVID-19
Getting ready for boards? Review these concise, bulleted high yield reviews for your exam.
USMLE & COMLEX-USA
Nurse Practitioner (NP)
Physician Assistant (PA)
Internal Medicine (ABIM)
References
Alimi, Y., W.S. Lim, L. Lansbury, J. Leonardi-Bee, and J.S. Nguyen-Van-Tam. "Systematic Review of Respiratory Viral Pathogens Identified in Adults with Community-Acquired Pneumonia in Europe." Journal of Clinical Virology 95 (October 2017): 26–35. https://doi.org/10.1016/j.jcv.2017.07.019.
CDC. "Prevent the Common Cold." Centers for Disease Control and Prevention, February 12, 2018. http://www.cdc.gov/features/rhinoviruses/index.html.
Cesario, Thomas C. "Viruses Associated With Pneumonia in Adults." Clinical Infectious Diseases 55, no. 1 (July 1, 2012): 107–13. https://doi.org/10.1093/cid/cis297.
Dandachi, Dima, and Maria C Rodriguez-Barradas. "Viral Pneumonia: Etiologies and Treatment." Journal of Investigative Medicine 66, no. 6 (August 2018): 957–65. https://doi.org/10.1136/jim-2018-000712.
Dasaraju, Purushothama V., and Chien Liu. "Infections of the Respiratory System." In Medical Microbiology, edited by Samuel Baron, 4th ed. Galveston (TX): University of Texas Medical Branch at Galveston, 1996. http://www.ncbi.nlm.nih.gov/books/NBK8142/.
"Flu Symptoms & Complications | CDC," December 19, 2018. https://www.cdc.gov/flu/consumer/symptoms.htm.
Franquet, Tomás. "Imaging of Pulmonary Viral Pneumonia." Radiology 260, no. 1 (July 2011): 18–39. https://doi.org/10.1148/radiol.11092149.
Guo, W, J Wang, M Sheng, M Zhou, and L Fang. "Radiological Findings in 210 Paediatric Patients with Viral Pneumonia: A Retrospective Case Study." The British Journal of Radiology 85, no. 1018 (October 2012): 1385–89. https://doi.org/10.1259/bjr/20276974.
Jain, Vardhmaan, and Abhishek Bhardwaj. "Pneumonia, Pathology." In StatPearls. Treasure Island (FL): StatPearls Publishing, 2018. http://www.ncbi.nlm.nih.gov/books/NBK526116/.
José, Ricardo J., Jimstan N. Periselneris, and Jeremy S. Brown. "Community-Acquired Pneumonia." Current Opinion in Pulmonary Medicine 21, no. 3 (May 2015): 212. https://doi.org/10.1097/MCP.0000000000000150.
Koo, Hyun Jung, Soyeoun Lim, Jooae Choe, Sang-Ho Choi, Heungsup Sung, and Kyung-Hyun Do. "Radiographic and CT Features of Viral Pneumonia." RadioGraphics 38, no. 3 (May 1, 2018): 719–39. https://doi.org/10.1148/rg.2018170048.
Musher, Daniel M., and Anna R. Thorner. "Community-Acquired Pneumonia." New England Journal of Medicine 371, no. 17 (October 23, 2014): 1619–28. https://doi.org/10.1056/NEJMra1312885.
Peltola, Ville, Terho Heikkinen, and Olli Ruuskanen. "CLINICAL COURSES OF CROUP CAUSED BY INFLUENZA AND PARAINFLUENZA VIRUSES." The Pediatric Infectious Disease Journal 21, no. 1 (January 2002): 76.
Petrocheilou, Argyri, Kalliopi Tanou, Efthimia Kalampouka, Georgia Malakasioti, Christos Giannios, and Athanasios G. Kaditis. "Viral Croup: Diagnosis and a Treatment Algorithm." Pediatric Pulmonology 49, no. 5 (May 1, 2014): 421–29. https://doi.org/10.1002/ppul.22993.
Rhedin, Samuel, Ann Lindstrand, Annie Hjelmgren, Malin Ryd-Rinder, Lars Öhrmalm, Thomas Tolfvenstam, Åke Örtqvist, et al. "Respiratory Viruses Associated with Community- Acquired Pneumonia in Children: Matched Case–Control Study," n.d., 7.
Rosychuk, Rhonda J., Terry P. Klassen, Donald C. Voaklander, Ambikaipakan Senthilselvan, and Brian H. Rowe. "Seasonality Patterns in Croup Presentations to Emergency Departments in Alberta, Canada: A Time Series Analysis." Pediatric Emergency Care 27, no. 4 (April 1, 2011): 256–60. https://doi.org/10.1097/PEC.0b013e31821314b0.
Shorr, Andrew F., Marya D. Zilberberg, Scott T. Micek, and Marin H. Kollef. "Viruses Are Prevalent in Non-Ventilated Hospital-Acquired Pneumonia." Respiratory Medicine 122 (January 2017): 76–80. https://doi.org/10.1016/j.rmed.2016.11.023.
Simoes, Eric A. F., Thomas Cherian, Jeffrey Chow, Sonbol A. Shahid-Salles, Ramanan Laxminarayan, and T. Jacob John. "Acute Respiratory Infections in Children." In Disease Control Priorities in Developing Countries, edited by Dean T. Jamison, Joel G. Breman, Anthony R. Measham, George Alleyne, Mariam Claeson, David B. Evans, Prabhat Jha, Anne Mills, and Philip Musgrove, 2nd ed. Washington (DC): World Bank, 2006. http://www.ncbi.nlm.nih.gov/books/NBK11786/.
Skolnik, Neil, and Phuong Tien. "Community-Acquired Pneumonia in Infants and Children." Family Practice News 41, no. 19 (November 2011): 22. https://doi.org/10.1016/S0300-7073(11)70974-4.
"Viral Infection Is Not Uncommon in Adult Patients with Severe Hospital-Acquired Pneumonia." Accessed January 21, 2019. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0095865.
Wallihan, Rebecca, and Octavio Ramilo. "Community-Acquired Pneumonia in Children: Current Challenges and Future Directions." Journal of Infection, Hot Topics in Infection and Immunity in Children - Papers from the 11th annual IIC meeting, Oxford, UK, 2013, 69 (November 1, 2014): S87–90. https://doi.org/10.1016/j.jinf.2014.07.021.
Witek, T. J., D. L. Ramsey, A. N. Carr, and D. K. Riker. "The Natural History of Community-Acquired Common Colds Symptoms Assessed over 4-Years." Rhinology 53, no. 1 (March 2015): 81–88. https://doi.org/10.4193/Rhin14.149.
Zar, H. J., and F. P. Polack. "Childhood Pneumonia: The Role of Viruses." Thorax 70, no. 9 (September 1, 2015): 811–12. https://doi.org/10.1136/thoraxjnl-2015-207320.