Rhinovirus

Classification

General Characteristics

Structure

• Picornavirus family
• RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology
• Positive-sense ssRNA Positive-sense ssRNA Hepatitis C Virus
• Naked

Basic features

• Very small: 30 nm
• Acid-labile → inactivated by gastric acid Gastric acid Hydrochloric acid present in gastric juice. Gastroesophageal Reflux Disease (GERD)
• Temperature for proliferation: 33–35°C (found in the nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose and Nasal Cavity: Anatomy)
• > 100 serotypes can cause upper respiratory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease (the common cold).
• Capable of surviving on hands for hours

Associated diseases

• Upper respiratory tract infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease
• Bronchiolitis Bronchiolitis Inflammation of the bronchioles. Pediatric Chest Abnormalities
• Rhinitis Rhinitis Inflammation of the nasal mucosa, the mucous membrane lining the nasal cavities. Rhinitis
• Otitis media
• Sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis
• Chronic bronchitis

Pathogenesis

Epidemiology

• Most common fall → spring
• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency 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 Reservoir Animate or inanimate sources which normally harbor disease-causing organisms and thus serve as potential sources of disease outbreaks. Reservoirs are distinguished from vectors (disease vectors) and carriers, which are agents of disease transmission rather than continuing sources of potential disease outbreaks. Humans may serve both as disease reservoirs and carriers. Escherichia coli.
• Aerosol particles
• Direct contact
• Fomites Fomites Inanimate objects that carry pathogenic microorganisms and thus can serve as the source of infection. Microorganisms typically survive on fomites for minutes or hours. Common fomites include clothing, tissue paper, hairbrushes, and cooking and eating utensils. Adenovirus (can retain the virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology from respiratory droplets Droplets Varicella-Zoster Virus/Chickenpox)
• Rhinovirus can survive outside a human host for up to 3 hours.

Risk factors

• Asthma Asthma Asthma is a chronic inflammatory respiratory condition characterized by bronchial hyperresponsiveness and airflow obstruction. The disease is believed to result from the complex interaction of host and environmental factors that increase disease predisposition, with inflammation causing symptoms and structural changes. Patients typically present with wheezing, cough, and dyspnea. Asthma
• Cystic fibrosis Cystic fibrosis Cystic fibrosis is an autosomal recessive disorder caused by mutations in the gene CFTR. The mutations lead to dysfunction of chloride channels, which results in hyperviscous mucus and the accumulation of secretions. Common presentations include chronic respiratory infections, failure to thrive, and pancreatic insufficiency. Cystic Fibrosis (CF)
• Chronic bronchitis
• Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD) ( COPD COPD Chronic obstructive pulmonary disease (COPD) is a lung disease characterized by progressive, largely irreversible airflow obstruction. The condition usually presents in middle-aged or elderly persons with a history of cigarette smoking. Signs and symptoms include prolonged expiration, wheezing, diminished breath sounds, progressive dyspnea, and chronic cough. Chronic Obstructive Pulmonary Disease (COPD))
• Infants and elderly individuals
• Immunocompromised immunocompromised A human or animal whose immunologic mechanism is deficient because of an immunodeficiency disorder or other disease or as the result of the administration of immunosuppressive drugs or radiation. Gastroenteritis individuals

Pathophysiology

• Incubation Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period: 1–3 days
• Inoculation in the nasal mucosa Nasal mucosa The mucous lining of the nasal cavity, including lining of the nostril (vestibule) and the olfactory mucosa. Nasal mucosa consists of ciliated cells, goblet cells, brush cells, small granule cells, basal cells (stem cells) and glands containing both mucous and serous cells. Nose and Nasal Cavity: Anatomy → attaches to the respiratory epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology and spreads locally → elicits an innate immune response Innate Immune Response Immunity to pathogens is divided into innate and adaptive immune responses. The innate immune response is the 1st line of defense against a variety of pathogens, including bacteria, fungi, viruses, and parasites. In essentially the same form, the innate type of immunity is present in all multicellular organisms. Innate Immunity: Barriers, Complement, and Cytokines leading to airway Airway ABCDE Assessment inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation and remodeling
• Few cells are actually infected by rhinovirus (only a small portion of the epithelium Epithelium The epithelium is a complex of specialized cellular organizations arranged into sheets and lining cavities and covering the surfaces of the body. The cells exhibit polarity, having an apical and a basal pole. Structures important for the epithelial integrity and function involve the basement membrane, the semipermeable sheet on which the cells rest, and interdigitations, as well as cellular junctions. Surface Epithelium: Histology is involved).

Prevention

• 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 Incubation The amount time between exposure to an infectious agent and becoming symptomatic. Rabies Virus period: 12–72 hours
• Duration: 7–10 days
• Infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease caused: 
  • Common cold (most often)
  • Ear infection
  • Sinus infection 
  • Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia and bronchiolitis Bronchiolitis Inflammation of the bronchioles. Pediatric Chest Abnormalities (rare)
• Symptoms:
  • Malaise Malaise Tick-borne Encephalitis Virus
  • Sore throat Sore throat Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis
  • Nasal discharge
  • Nasal congestion
  • Sneezing 
  • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
  • Facial and ear pressure
  • Hoarseness Hoarseness An unnaturally deep or rough quality of voice. Parapharyngeal Abscess

Diagnosis

• Diagnosis is established by clinical history and exam.
• Exam findings:
  • Red nose Nose The nose is the human body’s primary organ of smell and functions as part of the upper respiratory system. The nose may be best known for inhaling oxygen and exhaling carbon dioxide, but it also contributes to other important functions, such as tasting. The anatomy of the nose can be divided into the external nose and the nasal cavity. Nose and Nasal Cavity: Anatomy
  • Rhinorrhea Rhinorrhea Excess nasal drainage. Respiratory Syncytial Virus
  • Nasal mucous membranes appear glistening and glassy without obvious erythema Erythema Redness of the skin produced by congestion of the capillaries. This condition may result from a variety of disease processes. Chalazion or edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema.
  • The pharynx Pharynx The pharynx is a component of the digestive system that lies posterior to the nasal cavity, oral cavity, and larynx. The pharynx can be divided into the oropharynx, nasopharynx, and laryngopharynx. Pharyngeal muscles play an integral role in vital processes such as breathing, swallowing, and speaking. Pharynx: Anatomy typically appears normal.
• Testing options to obtain a specific diagnosis:
  • Direct antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination tests:
    • Severe acute respiratory syndrome coronavirus Coronavirus Coronaviruses are a group of related viruses that contain positive-sense, single-stranded RNA. Coronavirus derives its name from “κορώνη korṓnē” in Greek, which translates as “crown,” after the small club-shaped proteins visible as a ring around the viral envelope in electron micrographs. Coronavirus 2 (SARS-CoV-2)
    • Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza
    • Respiratory syncytial virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology ( RSV RSV Respiratory syncytial virus (RSV) is an enveloped, single-stranded, linear, negative-sense RNA virus of the family Paramyxoviridae and the genus Orthopneumovirus. Two subtypes (A and B) are present in outbreaks, but type A causes more severe disease. Respiratory syncytial virus causes infections of the lungs and respiratory tract. Respiratory Syncytial Virus)
    • Direct antigen Antigen Substances that are recognized by the immune system and induce an immune reaction. Vaccination test for parainfluenza and adenovirus Adenovirus Adenovirus (member of the family Adenoviridae) is a nonenveloped, double-stranded DNA virus. Adenovirus is transmitted in a variety of ways, and it can have various presentations based on the site of entry. Presentation can include febrile pharyngitis, conjunctivitis, acute respiratory disease, atypical pneumonia, and gastroenteritis. Adenovirus
  • PCR PCR Polymerase chain reaction (PCR) is a technique that amplifies DNA fragments exponentially for analysis. The process is highly specific, allowing for the targeting of specific genomic sequences, even with minuscule sample amounts. The PCR cycles multiple times through 3 phases: denaturation of the template DNA, annealing of a specific primer to the individual DNA strands, and synthesis/elongation of new DNA molecules. Polymerase Chain Reaction (PCR) assays: SARS-CoV-2

Management and Complications

Management

• Self-limited 
• Supportive care:
  • Rest
  • Hydration
  • NSAIDs NSAIDS Primary vs Secondary Headaches
  • Nasal decongestants
  • Antihistamines Antihistamines Antihistamines are drugs that target histamine receptors, particularly H1 and H2 receptors. H1 antagonists are competitive and reversible inhibitors of H1 receptors. First-generation antihistamines cross the blood-brain barrier and can cause sedation. Antihistamines

Complications

• Otitis media
• Sinusitis Sinusitis Sinusitis refers to inflammation of the mucosal lining of the paranasal sinuses. The condition usually occurs concurrently with inflammation of the nasal mucosa (rhinitis), a condition known as rhinosinusitis. Acute sinusitis is due to an upper respiratory infection caused by a viral, bacterial, or fungal agent. Sinusitis
• Exacerbation of reactive airway Airway ABCDE Assessment disease
• Lower respiratory tract infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease

Comparison of Species

Differential Diagnosis

• Rhinitis Rhinitis Inflammation of the nasal mucosa, the mucous membrane lining the nasal cavities. Rhinitis: inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation of the nasal mucosa Nasal mucosa The mucous lining of the nasal cavity, including lining of the nostril (vestibule) and the olfactory mucosa. Nasal mucosa consists of ciliated cells, goblet cells, brush cells, small granule cells, basal cells (stem cells) and glands containing both mucous and serous cells. Nose and Nasal Cavity: Anatomy. Rhinitis Rhinitis Inflammation of the nasal mucosa, the mucous membrane lining the nasal cavities. Rhinitis can be classified as infectious, allergic, or nonallergic based on the etiology. All 3 types present with nasal congestion, rhinorrhea Rhinorrhea Excess nasal drainage. Respiratory Syncytial Virus, and sneezing. The diagnosis is mainly clinical. Management includes antihistamines Antihistamines Antihistamines are drugs that target histamine receptors, particularly H1 and H2 receptors. H1 antagonists are competitive and reversible inhibitors of H1 receptors. First-generation antihistamines cross the blood-brain barrier and can cause sedation. Antihistamines, decongestants, and immunotherapy (“ allergy Allergy An abnormal adaptive immune response that may or may not involve antigen-specific IgE Type I Hypersensitivity Reaction shots”).
• Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza: a highly contagious respiratory disease presenting with fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, myalgia Myalgia Painful sensation in the muscles. Ion Channel Myopathy, headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, and symptoms of an upper respiratory infection Upper respiratory infection Rhinitis. Symptoms of gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis may also occur and are more common in children. Influenza Influenza Influenza viruses are members of the Orthomyxoviridae family and the causative organisms of influenza, a highly contagious febrile respiratory disease. There are 3 primary influenza viruses (A, B, and C) and various subtypes, which are classified based on their virulent surface antigens, hemagglutinin (HA) and neuraminidase (NA). Influenza typically presents with a fever, myalgia, headache, and symptoms of an upper respiratory infection. Influenza Viruses/Influenza is usually self-limited, though viral or secondary bacterial pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia may complicate the disease. Management is generally supportive, although neuraminidase Neuraminidase An enzyme that catalyzes the hydrolysis of alpha-2, 3, alpha-2, 6-, and alpha-2, 8-glycosidic linkages (at a decreasing rate, respectively) of terminal sialic residues in oligosaccharides, glycoproteins, glycolipids, colominic acid, and synthetic substrate. Antivirals for Influenza inhibitors can be administered early in the disease.
• Human parainfluenza viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology ( HPIVs HPIVs Human parainfluenza viruses (HPIVs) are single-stranded, linear, negative-sense RNA viruses of the family paramyxoviridae and the genus paramyxovirus. Human parainfluenza viruses are the 2nd most common cause of lower respiratory disease in children, after the respiratory syncytial virus. Parainfluenza Virus): single-stranded RNA RNA A polynucleotide consisting essentially of chains with a repeating backbone of phosphate and ribose units to which nitrogenous bases are attached. RNA is unique among biological macromolecules in that it can encode genetic information, serve as an abundant structural component of cells, and also possesses catalytic activity. RNA Types and Structure viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology in the Paramyxoviridae Paramyxoviridae A family of spherical viruses, of the order mononegavirales, somewhat larger than the orthomyxoviruses, and containing single-stranded RNA. Subfamilies include paramyxoviridae and pneumovirinae. Respiratory Syncytial Virus family, which can cause both upper and lower respiratory tract disease, including croup Croup Croup, also known as laryngotracheobronchitis, is a disease most commonly caused by a viral infection that leads to severe inflammation of the upper airway. It usually presents in children < 5 years of age. Patients develop a hoarse, "seal-like" barking cough and inspiratory stridor. Croup ( laryngotracheobronchitis Laryngotracheobronchitis Croup, also known as laryngotracheobronchitis, is a disease most commonly caused by a viral infection that leads to severe inflammation of the upper airway. It usually presents in children < 5 years of age. Patients develop a hoarse, "seal-like" barking cough and inspiratory stridor. Croup), bronchiolitis Bronchiolitis Inflammation of the bronchioles. Pediatric Chest Abnormalities, and pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia. Management is primarily supportive care.
• Adenoviruses: nonenveloped, double-stranded DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure viruses Viruses Minute infectious agents whose genomes are composed of DNA or RNA, but not both. They are characterized by a lack of independent metabolism and the inability to replicate outside living host cells. Virology typically causing mild respiratory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease (common cold symptoms). Adenoviruses can also cause conjunctivitis Conjunctivitis Conjunctivitis is a common inflammation of the bulbar and/or palpebral conjunctiva. It can be classified into infectious (mostly viral) and noninfectious conjunctivitis, which includes allergic causes. Patients commonly present with red eyes, increased tearing, burning, foreign body sensation, and photophobia. Conjunctivitis, atypical pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, gastroenteritis Gastroenteritis Gastroenteritis is inflammation of the stomach and intestines, commonly caused by infections from bacteria, viruses, or parasites. Transmission may be foodborne, fecal-oral, or through animal contact. Common clinical features include abdominal pain, diarrhea, vomiting, fever, and dehydration. Gastroenteritis, or appendicitis Appendicitis Appendicitis is the acute inflammation of the vermiform appendix and the most common abdominal surgical emergency globally. The condition has a lifetime risk of 8%. Characteristic features include periumbilical abdominal pain that migrates to the right lower quadrant, fever, anorexia, nausea, and vomiting. Appendicitis. Transmission is through aerosols Aerosols Colloids with a gaseous dispersing phase and either liquid (fog) or solid (smoke) dispersed phase; used in fumigation or in inhalation therapy; may contain propellant agents. Coxiella/Q Fever, fomites Fomites Inanimate objects that carry pathogenic microorganisms and thus can serve as the source of infection. Microorganisms typically survive on fomites for minutes or hours. Common fomites include clothing, tissue paper, hairbrushes, and cooking and eating utensils. Adenovirus, fecal-to-oral contact, and direct contact. Management is supportive. 
• Pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia: infection of the lower respiratory tract resulting in air sacs filling with fluid or pus. Symptoms include cough with phlegm, fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever, chills Chills The sudden sensation of being cold. It may be accompanied by shivering. Fever, and difficulty breathing. For bacterial causes, antibiotics are indicated in management. Some forms of pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, such as pneumococcal pneumonia Pneumonia Pneumonia or pulmonary inflammation is an acute or chronic inflammation of lung tissue. Causes include infection with bacteria, viruses, or fungi. In more rare cases, pneumonia can also be caused through toxic triggers through inhalation of toxic substances, immunological processes, or in the course of radiotherapy. Pneumonia, can be prevented by vaccines.