The classic symptoms of pertussis are a paroxysmal cough, inspiratory whoop, and fainting, or vomiting after coughing. The cough from pertussis has been documented to cause subconjunctival hemorrhages, rib fractures, urinary incontinence, hernias, and vertebral artery dissection. Violent coughing can cause the pleura to rupture, leading to a pneumothorax. Vomiting after a coughing spell or an inspiratory whooping sound on coughing, almost doubles the likelihood that the illness is pertussis. The absence of a paroxysmal cough or posttussive emesis, though, makes it almost half as likely.

The illness usually starts with mild respiratory symptoms, mild coughing, sneezing, or a runny nose. This is known as the catarrhal stage. After one to two weeks, the coughing classically develops into uncontrollable fits, each with five to ten forceful coughs, followed by a high-pitched "whoop" sound in younger children, or a gasping sound in older children, as the person tries to inhale (paroxysmal stage).

Coughing fits can occur on their own or can be triggered by yawning, stretching, laughing, eating, or yelling; they usually occur in groups, with multiple episodes on an hourly basis throughout the day. This stage usually lasts two to eight weeks, or sometimes longer. A gradual transition then occurs to the convalescent stage, which usually lasts one to four weeks. This stage is marked by a decrease in paroxysms of coughing, both in frequency and severity, and a cessation of vomiting. A tendency to produce the "whooping" sound after coughing may remain for a considerable period after the disease itself has cleared up.

The time between exposure and the development of symptoms is on average 7–14 days (range 6–20 days), rarely as long as 42 days.

Croup is characterized by a "barking" cough, stridor, hoarseness, and difficulty breathing which usually worsens at night. The "barking" cough is often described as resembling the call of a seal or sea lion. The stridor is worsened by agitation or crying, and if it can be heard at rest, it may indicate critical narrowing of the airways. As croup worsens, stridor may decrease considerably.

Other symptoms include fever, coryza (symptoms typical of the common cold), and indrawing of the chest wall–known as Hoover's sign. Drooling or a very sick appearance indicate other medical conditions, such as epiglottitis.

The incubation period is 5–7 days (with a range of 3–10). Symptoms can include a harsh, dry cough, retching, sneezing, snorting, gagging or vomiting in response to light pressing of the trachea or after excitement or exercise. The presence of a fever varies from case to case.

Although kennel cough is considered to be a multifactorial infection, there are two main forms. The first is more mild and is caused by B. bronchiseptica and canine parainfluenza virus infections, without complications from canine distemper virus (CDV) or canine adenovirus (CAV). This form occurs most regularly in autumn, and can be distinguished by symptoms such as a retching cough and vomiting. The second form has a more complex combination of causative organisms including CDV and CAV. It typically occurs in dogs that have not been vaccinated and it is not seasonal. Symptoms are more severe than the first form, and may include rhinitis, conjunctivitis, and fever in addition to a hacking cough.

Croup is usually deemed to be due to a viral infection. Others use the term more broadly, to include acute laryngotracheitis, spasmodic croup, laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis. The first two conditions involve a viral infection and are generally milder with respect to symptomatology; the last four are due to bacterial infection and are usually of greater severity.

Bronchitis may be indicated by an expectorating cough, shortness of breath (dyspnea), and wheezing. On occasion, chest pains, fever, and fatigue or malaise may also occur. In addition, bronchitis caused by Adenoviridae may cause systemic and gastrointestinal symptoms as well. However, the coughs due to bronchitis can continue for up to three weeks or more even after all other symptoms have subsided.

The symptoms of diphtheria usually begin two to seven days after infection. Symptoms of diphtheria include fever of 38 °C (100.4 °F) or above, chills, fatigue, bluish skin coloration (cyanosis), sore throat, hoarseness, cough, headache, difficulty swallowing, painful swallowing, difficulty breathing, rapid breathing, foul-smelling and bloodstained nasal discharge, and lymphadenopathy. Within two to three days, diphtheria may destroy healthy tissues in the respiratory system. The dead tissue forms a thick, gray coating that can build up in the throat or nose. This thick gray coating is called a “pseudomembrane.” It can cover tissues in the nose, tonsils, voice box, and throat, making it very hard to breathe and swallow. Symptoms can also include cardiac arrhythmias, myocarditis, and cranial and peripheral nerve palsies.

People with infectious pneumonia often have a productive cough, fever accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, and an increased rate of breathing. In the elderly, confusion may be the most prominent sign.

The typical signs and symptoms in children under five are fever, cough, and fast or difficult breathing. Fever is not very specific, as it occurs in many other common illnesses, may be absent in those with severe disease, malnutrition or in the elderly. In addition, a cough is frequently absent in children less than 2 months old. More severe signs and symptoms in children may include blue-tinged skin, unwillingness to drink, convulsions, ongoing vomiting, extremes of temperature, or a decreased level of consciousness.

Bacterial and viral cases of pneumonia usually present with similar symptoms. Some causes are associated with classic, but non-specific, clinical characteristics. Pneumonia caused by "Legionella" may occur with abdominal pain, diarrhea, or confusion, while pneumonia caused by "Streptococcus pneumoniae" is associated with rusty colored sputum, and pneumonia caused by "Klebsiella" may have bloody sputum often described as "currant jelly". Bloody sputum (known as hemoptysis) may also occur with tuberculosis, Gram-negative pneumonia, and lung abscesses as well as more commonly with acute bronchitis. "Mycoplasma" pneumonia may occur in association with swelling of the lymph nodes in the neck, joint pain, or a middle ear infection. Viral pneumonia presents more commonly with wheezing than does bacterial pneumonia. Pneumonia was historically divided into "typical" and "atypical" based on the belief that the presentation predicted the underlying cause. However, evidence has not supported this distinction, thus it is no longer emphasized.

Pneumonia occurs when the lungs become infected, causing inflammation (swelling). Symptoms of pneumonia usually include:

- Fever (but older people may have lower than normal body temperature)

- Cough

- Shortness of breath

- Chills

- Sweating

- Chest pain that comes and goes with breathing

- Headache

- Muscle pain

- Excessive tiredness

- Nails may turn blue from lack of oxygen

Laryngeal diphtheria can lead to a characteristic swollen neck and throat, or "bull neck". The swollen throat is often accompanied by a serious respiratory condition, characterized by a brassy or "barking" cough, stridor, hoarseness, and difficulty breathing, and historically referred to variously as "diphtheritic croup", "true croup", or sometimes simply as "croup". Diphtheritic croup is extremely rare in countries where diphtheria vaccination is customary. As a result, the term "croup" nowadays most often refers to an unrelated viral illness that produces similar but milder respiratory symptoms.

Haemophilus influenzae (formerly called Pfeiffer's bacillus or Bacillus influenzae) is a Gram-negative, coccobacillary, facultatively anaerobic pathogenic bacterium belonging to the "Pasteurellaceae" family. "H. influenzae" was first described in 1892 by Richard Pfeiffer during an influenza pandemic.

The bacterium was mistakenly considered to be the cause of influenza until 1933 when the viral cause of influenza became apparent, and is still colloquially known as 'bacterial influenza'. "H. influenzae" is responsible for a wide range of localized and invasive infections. This species was the first free-living organism to have its entire genome sequenced.

Acute bronchitis usually lasts a few days or weeks. It may accompany or closely follow a cold or the flu, or may occur on its own. Bronchitis usually begins with a dry cough, including waking the sufferer at night. After a few days, it progresses to a wetter or productive cough, which may be accompanied by fever, fatigue, and headache. The fever, fatigue, and malaise may last only a few days, but the wet cough may last up to several weeks.

Should the cough last longer than a month, some physicians may issue a referral to an otorhinolaryngologist (ear, nose and throat doctor) to see if a condition other than bronchitis is causing the irritation. It is possible that having irritated bronchial tubes for as long as a few months may inspire asthmatic conditions in some patients.

In addition, if one starts coughing mucus tinged with blood, one should see a physician. In rare cases, physicians may conduct tests to see whether the cause of the bloody sputum is a serious condition such as tuberculosis or lung cancer.

Lower respiratory tract infection (LRTI), while often used as a synonym for pneumonia, can also be applied to other types of infection including lung abscess and acute bronchitis. Symptoms include shortness of breath, weakness, fever, coughing and fatigue.

There are a number of symptoms that are characteristic of lower respiratory tract infections. The two most common are bronchitis and edema. Influenza affects both the upper and lower respiratory tracts.

Antibiotics are the first line treatment for pneumonia; however, they are not effective or indicated for parasitic or viral infections. Acute bronchitis typically resolves on its own with time.

In 2015 there were about 291 million cases. These resulted in 2.74 million deaths down from 3.4 million deaths in 1990. This was 4.8% of all deaths in 2013.

Bronchitis describes the swelling or inflammation of the bronchial tubes. Additionally, bronchitis is described as either acute or chronic depending on its presentation and is also further described by the causative agent. Acute bronchitis can be defined as acute bacterial or viral infection of the larger airways in healthy patients with no history of recurrent disease. It affects over 40 adults per 1000 each year and consists of transient inflammation of the major bronchi and trachea. Most often it is caused by viral infection and hence antibiotic therapy is not indicated in immunocompetent individuals. Viral bronchitis can sometimes be treated using antiviral medications depending on the virus causing the infection, and medications such as anti-inflammatory drugs and expectorants can help mitigate the symptoms. Treatment of acute bronchitis with antibiotics is common but controversial as their use has only moderate benefit weighted against potential side effects (nausea and vomiting), increased resistance, and cost of treatment in a self-limiting condition. Beta2 agonists are sometimes used to relieve the cough associated with acute bronchitis. In a recent systematic review it was found there was no evidence to support their use.

Acute bronchitis, also known as a chest cold, is short term inflammation of the bronchi of the lungs. The most common symptom is a cough. Other symptoms include coughing up mucus, wheezing, shortness of breath, fever, and chest discomfort. The infection may last from a few to ten days. The cough may persist for several weeks afterwards with the total duration of symptoms usually around three weeks. Some have symptoms for up to six weeks.

Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli. Typically symptoms include some combination of productive or dry cough, chest pain, fever, and trouble breathing. Severity is variable.

Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications and conditions such as autoimmune diseases. Risk factors include other lung diseases such as cystic fibrosis, COPD, and asthma, diabetes, heart failure, a history of smoking, a poor ability to cough such as following a stroke, or a weak immune system. Diagnosis is often based on the symptoms and physical examination. Chest X-ray, blood tests, and culture of the sputum may help confirm the diagnosis. The disease may be classified by where it was acquired with community, hospital, or health care associated pneumonia.

Vaccines to prevent certain types of pneumonia are available. Other methods of prevention include handwashing and not smoking. Treatment depends on the underlying cause. Pneumonia believed to be due to bacteria is treated with antibiotics. If the pneumonia is severe, the affected person is generally hospitalized. Oxygen therapy may be used if oxygen levels are low.

Pneumonia affects approximately 450 million people globally (7% of the population) and results in about 4 million deaths per year. Pneumonia was regarded by William Osler in the 19th century as "the captain of the men of death". With the introduction of antibiotics and vaccines in the 20th century, survival improved. Nevertheless, in developing countries, and among the very old, the very young, and the chronically ill, pneumonia remains a leading cause of death. Pneumonia often shortens suffering among those already close to death and has thus been called "the old man's friend".

One possible cause for post-viral cough is that the receptors that are responsible for stimulating the cough during the respiratory tract infection are up-regulated by respiratory tract infection and continue to stimulate even after the virus has disappeared.

In uncomplicated colds, cough and nasal discharge may persist for 14 days or more even after other symptoms have resolved.

Acute upper respiratory tract infections include rhinitis, pharyngitis/tonsillitis and laryngitis often referred to as a common cold, and their complications: sinusitis, ear infection and sometimes bronchitis (though bronchi are generally classified as part of the lower respiratory tract.) Symptoms of URTIs commonly include cough, sore throat, runny nose, nasal congestion, headache, low-grade fever, facial pressure and sneezing.

Symptoms of rhinovirus in children usually begin 1–3 days after exposure. The illness usually lasts 7–10 more days.

Color or consistency changes in mucous discharge to yellow, thick, or green are the natural course of viral upper respiratory tract infection and not an indication for antibiotics.

Group A beta hemolytic streptococcal pharyngitis/tonsillitis (strep throat) typically presents with a sudden onset of sore throat, pain with swallowing and fever. Strep throat does not usually cause runny nose, voice changes, or cough.

Pain and pressure of the ear caused by a middle ear infection (otitis media) and the reddening of the eye caused by viral conjunctivitis are often associated with upper respiratory infections.

A URI may be classified by the area inflamed.

Rhinitis affects the nasal mucosa, while rhinosinusitis or sinusitis affects the nose and paranasal sinuses, including frontal, ethmoid, maxillary, and sphenoid sinuses. Nasopharyngitis (rhinopharyngitis or the common cold) affects the nares, pharynx, hypopharynx, uvula, and tonsils generally. Without involving the nose, pharyngitis inflames the pharynx, hypopharynx, uvula, and tonsils. Similarly, epiglottitis (supraglottitis) inflames the superior portion of the larynx and supraglottic area; laryngitis is in the larynx; laryngotracheitis is in the larynx, trachea, and subglottic area; and tracheitis is in the trachea and subglottic area.

In a typical case, an infant under two years of age develops cough, wheeze, and shortness of breath over one or two days. Crackles or wheeze are typical findings on listening to the chest with a stethoscope. The infant may be breathless for several days. After the acute illness, it is common for the airways to remain sensitive for several weeks, leading to recurrent cough and wheeze.

Some signs of severe disease include:

- poor feeding (less than half of usual fluid intake in preceding 24 hours)

- significantly decreased activity

- history of stopping breathing

- respiratory rate >70/min

- presence of nasal flaring and/or grunting

- severe chest wall recession (Hoover's sign)

- bluish skin

"Streptococcus pneumoniae" () is the most common bacterial cause of pneumonia in all age groups except newborn infants. "Streptococcus pneumoniae" is a Gram-positive bacterium that often lives in the throat of people who do not have pneumonia.

Other important Gram-positive causes of pneumonia are "Staphylococcus aureus" () and "Bacillus anthracis".

Chronic bronchitis is defined as a productive cough that lasts for three months or more per year for at least two years. Most people with chronic bronchitis have chronic obstructive pulmonary disease (COPD). Protracted bacterial bronchitis is defined as a chronic productive cough with a positive bronchoalveolar lavage that resolves with antibiotics. Symptoms of chronic bronchitis may include wheezing and shortness of breath, especially upon exertion and low oxygen saturations. The cough is often worse soon after awakening and the sputum produced may have a yellow or green color and may be streaked with specks of blood.

Pneumonia occurs in a variety of situations and treatment must vary according to the situation. It is classified as either community or hospital acquired depending on where the patient contracted the infection. It is life-threatening in the elderly or those who are immunocompromised. The most common treatment is antibiotics and these vary in their adverse effects and their effectiveness. Pneumonia is also the leading cause of death in children less than five years of age in low income countries. The most common cause of pneumonia is pneumococcal bacteria, "Streptococcus pneumoniae" accounts for 2/3 of bacteremic pneumonias. This is a dangerous type of lung infection with a mortality rate of around 25%.

For optimal management of a pneumonia patient, the following must be assessed: pneumonia severity (including treatment location, e.g., home, hospital or intensive care), identification of causative organism, analgesia of chest pain, the need for supplemental oxygen, physiotherapy, hydration, bronchodilators and possible complications of emphysema or lung abscess.

Post-viral cough can be resistant to treatment. Post-viral cough usually goes away on its own; however, cough suppressants containing codeine may be prescribed. A study has claimed theobromine in dark chocolate is more effective.

Gram-negative bacteria are seen less frequently: "Haemophilus influenzae" (), "Klebsiella pneumoniae" (), "Escherichia coli" (), "Pseudomonas aeruginosa" (), "Bordetella pertussis", and "Moraxella catarrhalis" are the most common.

These bacteria often live in the gut and enter the lungs when contents of the gut (such as vomit or faeces) are inhaled.