Classification
RNA virus identification:
Viruses can be classified in many ways. Most viruses have a genome formed by either DNA or RNA. Viruses of the RNA genome can be further characterized by either a single- or double-stranded RNA. “Enveloped” viruses are covered by a thin coat of cell membrane (usually taken from the host cell). If the coat is absent, the viruses are called “naked” viruses. Viruses with single-stranded genomes are “positive-sense” viruses if the genome is directly employed as mRNA, which is translated into proteins. “Negative-sense,” single-stranded viruses employ RNA-dependent RNA polymerase, a viral enzyme, to transcribe the genome into mRNA.
General Characteristics
Structure
- Picornavirus family
- RNA virus
- Positive-sense ssRNA
- Naked
Basic features
- Very small: 30 nm
- Acid-labile → inactivated by gastric acid
- Temperature for proliferation: 33–35°C (found in the nose)
- > 100 serotypes can cause upper respiratory infections (the common cold).
- Capable of surviving on hands for hours
Associated diseases
- Upper respiratory tract infections
- Bronchiolitis
- Rhinitis
- Otitis media
- Sinusitis
- Chronic bronchitis
Pathogenesis
Epidemiology
- Most common fall → spring
- Incidence is highest in children in preschool and elementary school (average 3–8 colds per year).
- Adults typically have 2–4 colds per year.
Transmission
- Humans are the only reservoir.
- Aerosol particles
- Direct contact
- Fomites (can retain the virus from respiratory droplets)
- Rhinovirus can survive outside a human host for up to 3 hours.
Risk factors
- Asthma
- Cystic fibrosis (CF)
- Chronic bronchitis
- Chronic obstructive pulmonary disease (COPD)
- Infants and elderly individuals
- Immunocompromised individuals
Pathophysiology
- Incubation period: 1–3 days
- Inoculation in the nasal mucosa → attaches to the respiratory epithelium and spreads locally → elicits an innate immune response leading to airway inflammation and remodeling
- Few cells are actually infected by rhinovirus (only a small portion of the epithelium is involved).
Pathophysiology of a rhinovirus infection
Image by Lecturio. License: CC BY-NC-SA 4.0Prevention
- Wash hands with soap and water.
- Disinfect hands and surfaces.
- Avoid contact of the face with the hands.
- Wear a mask (e.g., surgical, KN95, FFP2).
Clinical Presentation
- Incubation period: 12–72 hours
- Duration: 7–10 days
- Infections caused:
- Common cold (most often)
- Ear infection
- Sinus infection
- Pneumonia and bronchiolitis (rare)
- Symptoms:
- Malaise
- Sore throat
- Nasal discharge
- Nasal congestion
- Sneezing
- Headache
- Facial and ear pressure
- Hoarseness
Diagnosis
- Diagnosis is established by clinical history and exam.
- Exam findings:
- Red nose
- Rhinorrhea
- Nasal mucous membranes appear glistening and glassy without obvious erythema or edema.
- The pharynx typically appears normal.
- Testing options to obtain a specific diagnosis:
- Direct antigen tests:
- Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
- Influenza
- Respiratory syncytial virus (RSV)
- Direct antigen test for parainfluenza and adenovirus
- PCR assays: SARS-CoV-2
- Direct antigen tests:
Management and Complications
Management
- Self-limited
- Supportive care:
- Rest
- Hydration
- NSAIDs
- Nasal decongestants
- Antihistamines
Complications
- Otitis media
- Sinusitis
- Exacerbation of reactive airway disease
- Lower respiratory tract infections
Comparison of Species
| Symptom | Coronavirus (COVID-19) | Influenza virus (flu) | Rhinovirus (common cold) | Seasonal allergies |
|---|---|---|---|---|
| Fever | Often | Often | Rare | Rare |
| Fatigue | Often | Often | Sometimes | Often |
| Cough | Often | Often | Sometimes | Often |
| Sneezing | Rare | No | Often | Often |
| Myalgias | Sometimes | Often | Sometimes | No |
| Rhinorrhea or nasal congestion | Rare | Sometimes | Often | Often |
| Sore throat | Sometimes | Sometimes | Often | No |
| Diarrhea | Rare | Sometimes | No | No |
| Headache | Sometimes | Often | Often | Sometimes |
| Dyspnea | Often | Rare | Rare | Rare |
| Loss of taste and smell | Often | Rare | Sometimes | Rare |
Differential Diagnosis
- Rhinitis: inflammation of the nasal mucosa. Rhinitis can be classified as infectious, allergic, or nonallergic based on the etiology. All 3 types present with nasal congestion, rhinorrhea, and sneezing. The diagnosis is mainly clinical. Management includes antihistamines, decongestants, and immunotherapy (“allergy shots”).
- Influenza: a highly contagious respiratory disease presenting with fever, myalgia, headache, and symptoms of an upper respiratory infection. Symptoms of gastroenteritis may also occur and are more common in children. Influenza is usually self-limited, though viral or secondary bacterial pneumonia may complicate the disease. Management is generally supportive, although neuraminidase inhibitors can be administered early in the disease.
- Human parainfluenza viruses (HPIVs): single-stranded RNA viruses in the Paramyxoviridae family, which can cause both upper and lower respiratory tract disease, including croup (laryngotracheobronchitis), bronchiolitis, and pneumonia. Management is primarily supportive care.
- Adenoviruses: nonenveloped, double-stranded DNA viruses typically causing mild respiratory infections (common cold symptoms). Adenoviruses can also cause conjunctivitis, atypical pneumonia, gastroenteritis, or appendicitis. Transmission is through aerosols, fomites, fecal-to-oral contact, and direct contact. Management is supportive.
- Pneumonia: infection of the lower respiratory tract resulting in air sacs filling with fluid or pus. Symptoms include cough with phlegm, fever, chills, and difficulty breathing. For bacterial causes, antibiotics are indicated in management. Some forms of pneumonia, such as pneumococcal pneumonia, can be prevented by vaccines.
References
- Pappas, D. (2019). Epidemiology, clinical manifestations, and pathogenesis of rhinovirus infections. UpToDate. Retrieved Feb 27, 2021 from https://www.uptodate.com/contents/epidemiology-clinical-manifestations-and-pathogenesis-of-rhinovirus-infections
- Buensalido, J. (2019). Rhinovirus (RV) Infection (Common Cold). Emedicine. Retrieved Feb 27, 2021 from https://emedicine.medscape.com/article/227820-overview
- Martin ET, Fairchok MP, Stednick ZJ, Kuypers J, Englund JA. Epidemiology of multiple respiratory viruses in childcare attendees. J Infect Dis. 2013 Mar. 207(6):982-9.
- Makris, S, & Johnston, S. (2018). Recent advances in understanding rhinovirus immunity. F1000Research, 7, F1000 Faculty Rev-1537. https://doi.org/10.12688/f1000research.15337.1
