OVERVIEW

What is a respiratory tract infection?

A respiratory tract infection refers to an infection caused by pathogens such as viruses, bacteria, fungi, or parasites invading the human respiratory tract. Clinical symptoms include coughing, phlegm production, sneezing, runny nose, sore throat, fatigue, fever, and body aches.

Respiratory tract infection is a broad term and can be further divided into upper respiratory tract infections and lower respiratory tract infections. Infections in different parts of the respiratory tract vary in symptoms and severity, and treatment methods also differ.

If the respiratory tract infection is caused by a virus, it can usually resolve on its own without antimicrobial treatment. Infections caused by other pathogens can be treated with corresponding antimicrobial drugs, such as antibiotics or antifungals.

Are respiratory tract infections common?

They are very common, with higher incidence rates in winter and spring. The general population is susceptible, but children, the elderly, immunocompromised individuals, and those with chronic diseases are more prone to infection.

What is the respiratory tract in respiratory tract infections?

The respiratory tract refers to the passage through which air travels during breathing. It includes the nose, pharynx, larynx, trachea, and bronchi. The respiratory tract can be divided into upper and lower parts: the nose, pharynx, and larynx are collectively called the upper respiratory tract, while the trachea and bronchi are the lower respiratory tract.

The upper respiratory tract serves as the gateway for air to enter the lower respiratory tract, warming, humidifying, and filtering inhaled air. The lower respiratory tract not only transports air but also partially facilitates gas exchange.

Upper and lower respiratory tract infections present different symptoms. This classification helps in disease diagnosis and selecting appropriate treatment methods. Generally, upper respiratory tract infections are milder and less harmful.

What role does the respiratory tract play in respiratory tract infections?

The respiratory tract surface contains mucus and cilia, which warm, humidify, and purify inhaled air. Mucus traps dust and pathogens from the air, which are then expelled through the mouth via ciliary movement, preventing harmful substances from entering the lungs and protecting the body.

Respiratory tract infections can be divided into upper and lower respiratory tract infections. What is an upper respiratory tract infection? Is it a cold?

An upper respiratory tract infection (URI) refers to acute inflammation caused by pathogens such as viruses (the majority cause), bacteria, fungi, or parasites invading the nose, pharynx, or larynx. It is the most common infectious disease, accounting for over half of acute respiratory illnesses.

URIs are usually mild, short-lived, self-limiting, and have a good prognosis.

The common cold (often called a cold) is the most typical type of URI. Other URIs include influenza, viral pharyngitis, herpangina, pharyngoconjunctivitis, and bacterial pharyngotonsillitis.

Respiratory tract infections can be divided into upper and lower respiratory tract infections. What is a lower respiratory tract infection?

A lower respiratory tract infection (LRI) refers to diseases caused by pathogens such as bacteria, viruses, fungi, or parasites invading the trachea and bronchi. LRIs include tracheobronchitis, pneumonia, and others.

What is pneumonia in respiratory tract infections?

Pneumonia is a type of lower respiratory tract infection, referring to inflammation of the terminal airways, alveoli, and lung interstitium. It can be caused by pathogens such as bacteria, viruses, parasites, or fungi, as well as chemical or physical factors like radiation.

Bacterial pneumonia is the most common type, and the term "pneumonia" in daily usage usually refers to this form.

In respiratory tract infections, are the common cold and influenza the same thing?

Clearly not. Although both are colds, they differ significantly in nature and should not be confused.

• Influenza is caused by the influenza virus, has a sudden onset, and often involves high fever, especially in vulnerable groups like the elderly and children. If diagnosed, prompt hospitalization and antiviral treatment are necessary, as it can be life-threatening. The influenza virus is highly contagious, often causing outbreaks in communities.

• The common cold is a URI caused by viruses other than influenza. Symptoms are milder than influenza, and antiviral treatment is usually unnecessary. With adequate rest and symptomatic medication, recovery typically occurs within 1–2 weeks.

SYMPTOMS

What are the manifestations of upper respiratory tract infections in respiratory infections?

Common symptoms include sneezing, runny nose, sore throat, fatigue, fever, etc.

What are the common cold symptoms of upper respiratory tract infections in respiratory infections?

The common cold mainly manifests as nasal symptoms, such as coughing, sneezing, nasal congestion, runny nose, etc., and in severe cases, fever may occur.

Generally, it resolves on its own within 5–7 days, but people with poor immunity or those with other chronic respiratory diseases may experience a longer course of illness.

What are the manifestations of acute viral pharyngitis and laryngitis in upper respiratory tract infections?

Main symptoms include throat-related issues, such as throat itching and burning sensation, mild sore throat, significant hoarseness, difficulty speaking, etc.

What are the manifestations of acute herpetic pharyngitis in upper respiratory tract infections?

Severe sore throat and fever, with a course of about one week, which can resolve on its own. This disease usually occurs in summer, and children are more susceptible to it.

What are the symptoms of acute pharyngoconjunctivitis in upper respiratory tract infections?

Fever, sore throat, tearing when exposed to light, and obvious congestion of the pharynx and conjunctiva. It often occurs in summer, usually caused by adenovirus or Coxsackievirus infection during swimming, and is more common in children.

What are the manifestations of acute pharyngotonsillitis in upper respiratory tract infections?

Sudden onset, obvious sore throat, fever, chills, with body temperature possibly exceeding 39°C.

What other diseases can upper respiratory tract infections in respiratory infections cause?

Most patients have mild conditions and recover within one or two weeks without causing other diseases.

If treatment is delayed or improper, complications such as sinusitis, otitis media, conjunctivitis, cervical lymphadenitis, or abscesses in the retropharyngeal or lateral wall may occur.

Elderly or weak individuals are more prone to systemic inflammatory symptoms like bronchitis, pneumonia, sepsis, nephritis, or viral myocarditis. These conditions are more severe than upper respiratory infections themselves. For example, viral myocarditis can sometimes lead to sudden death, so patients with upper respiratory infections who experience chest tightness should be closely monitored and given sufficient attention.

In respiratory infections, what symptoms may suggest tracheobronchitis as a lower respiratory tract infection?

Tracheobronchitis has low specificity and often coexists with upper respiratory infections, sharing similar symptoms such as nasal congestion, runny nose, sneezing, and sore throat. Sometimes, mild chills, elevated body temperature, and general body aches may also occur.

Unlike upper respiratory infections, tracheobronchitis initially presents with mild coughing and little sputum. After one or two days, coughing worsens, and thick sputum is produced. Severe patients may experience bouts of intense coughing in the morning, after inhaling cold air, or after physical activity. Nausea and vomiting may sometimes accompany coughing.

What are the manifestations of pneumonia in respiratory infections?

Pneumonia is one of the most common respiratory diseases, with various types, each having unique symptoms. Generally, pneumonia presents with coughing, sputum production, difficulty breathing, shortness of breath, chest tightness, and fever. When the pleura is affected, chest pain may occur and worsen with breathing or changes in body position.

Some types of pneumonia may also cause nausea, vomiting, general fatigue, loss of appetite, or diarrhea. Severe pneumonia can lead to shock symptoms such as coma and low blood pressure, which can be life-threatening if not treated promptly.

CAUSES

What are the causes of respiratory infections?

Pathogens such as bacteria, viruses, fungi, and parasites invading the respiratory tract can cause respiratory infections. 70%–80% of upper respiratory infections are caused by viruses, mainly influenza viruses, parainfluenza viruses, etc., with a minority being bacterial.

Who is more susceptible to respiratory infections?

We all know that there are many pathogens like bacteria, viruses, and parasites in the external environment. However, when the body's immunity is normal, it can resist most pathogens. When the overall or respiratory defense capabilities decline, the body's resistance to external threats weakens, making it easier to contract respiratory diseases.

Therefore, elderly people and children with weakened immunity, as well as those with chronic respiratory diseases such as asthma, chronic obstructive pulmonary disease, sinusitis, or tonsillitis, are more likely to develop infections and experience more severe symptoms after exposure to pathogens.

Under what circumstances are respiratory infections more likely to occur?

Factors such as getting caught in the rain, exposure to cold, excessive fatigue, mental stress, and malnutrition can lower the body's immune capacity, making respiratory infections more likely to occur.

Are respiratory infections contagious?

Respiratory infections are contagious and primarily spread in two ways: direct inhalation of pathogen-containing droplets or hand-to-nose transmission after contact with a patient's secretions.

For example, if a healthy person comes into contact with the saliva or phlegm of someone with a respiratory infection, their hands may carry pathogens. If they then touch their nose directly, the pathogens can enter the nasal cavity and infect the body.

DIAGNOSIS

How do doctors diagnose upper respiratory tract infections in respiratory infectious diseases?

Generally, doctors diagnose upper respiratory tract infections by asking about nasopharyngeal symptoms (such as sneezing, runny nose, sore throat, fever, etc.) and combining them with physical examinations (including measuring body temperature, examining the throat, and auscultating the heart and lungs). Sometimes, doctors may also request blood tests or sputum examinations to assess the severity of the disease and identify the type of pathogen. If abnormal lung sounds are detected during auscultation, a chest X-ray may be performed to rule out lower respiratory tract infections.

Which diseases with similar symptoms should upper respiratory tract infections be differentiated from in respiratory infectious diseases?

Upper respiratory infections must be distinguished from other diseases that initially present with cold-like symptoms.

• Allergic rhinitis: The symptoms of allergic rhinitis are very similar to those of the common cold. The difference is that allergic rhinitis is often triggered by allergens such as dust, animal dander, temperature changes, pollen, or unusual odors, leading to a rapid onset and frequent, continuous sneezing. In contrast, colds usually involve only a few sneezes before stopping. During an allergic rhinitis episode, sneezing persists, accompanied by nasal itching. Symptoms improve within minutes to 1–2 hours after avoiding the allergen.

• Acute bronchitis: This presents with coughing and phlegm, with milder nasal symptoms. Blood tests and chest X-rays can help differentiate the diagnosis.

• Prodromal symptoms of acute infectious diseases: Diseases such as measles, polio, and encephalitis often exhibit respiratory symptoms in their early stages, along with their own unique manifestations. If the patient lives in an area with a high prevalence of these diseases or during an outbreak season, these conditions should be considered. Laboratory tests such as blood tests or cerebrospinal fluid examinations may be necessary for differentiation.

What tests should be performed for patients suspected of having tracheobronchitis, a lower respiratory tract infection?

Mild to moderate cases only require a chest X-ray and blood test. For severe cases, bacteriological tests and drug sensitivity tests are needed to guide clinical treatment.

Which diseases should tracheobronchitis be differentiated from in respiratory infectious diseases?

Tracheobronchitis lacks specificity and shares symptoms with pneumonia, tuberculosis, lung abscess, lung cancer, and acute infectious diseases such as measles, whooping cough, and tonsillitis. Differentiation can be based on factors such as living or working in epidemic-prone areas, the season, age, smoking history, vaccination status, and distinctive symptoms like tuberculous toxic symptoms or chest pain.

What tests are needed when pneumonia is suspected in respiratory infectious diseases?

• Blood test.

• Chest X-ray.

• Microbiological cultures of sputum and blood.

Which diseases share similar symptoms with pneumonia in respiratory infections?

• Tuberculosis: Often accompanied by systemic toxic symptoms such as low-grade fever in the afternoon, night sweats, fatigue, weight loss, insomnia, and palpitations. Generally ineffective against antibacterial treatments.

• Lung cancer: Typically lacks acute infectious symptoms but may involve hemoptysis or blood-streaked sputum. It can be complicated by obstructive pneumonia, which may respond poorly to antibiotics. Older patients or those with a smoking history exhibiting these symptoms should be highly suspected of lung cancer.

• Acute lung abscess: Unlike pneumonia, a large amount of foul-smelling purulent sputum is coughed up in the middle to late stages.

• Pulmonary thromboembolism: Often associated with risk factors for venous thrombosis, such as thrombophlebitis, cardiopulmonary diseases, trauma, surgery, or tumors. Symptoms may include hemoptysis, syncope, and dyspnea.

• Non-infectious pulmonary infiltrates: Such as pulmonary fibrosis, pulmonary edema, atelectasis, eosinophilic lung disease, and vasculitis.

To confirm the diagnosis and guide treatment, tests such as sputum analysis, tuberculin tests, chest CT, bronchoscopy, and cytology may be required for the above diseases.

TREATMENT

Which department should I visit for respiratory tract infections?

You should go to the Respiratory Medicine department. If the hospital does not have specialized departments, visit the General Internal Medicine department.

How to treat respiratory tract infections?

Most respiratory tract infections are caused by viruses, and there are currently no specific antiviral drugs. Treatment is mainly symptomatic, including rest, drinking plenty of water, quitting smoking, maintaining air circulation, supplementing nutrition, and moderate exercise.

• Symptomatic treatment: For high fever, antipyretic and analgesic drugs such as acetaminophen or ibuprofen can be used. Symptoms like sneezing, nasal congestion, runny nose, and severe coughing can also be treated with corresponding medications.

• Antibacterial treatment: If there is a bacterial infection, antibiotics such as penicillin, first-generation cephalosporins, spiramycin, or ofloxacin may be used. Antibiotics are generally not needed for viral infections.

Can patients with tracheobronchitis in respiratory tract infections recover completely?

Most patients respond well to treatment, but a few may experience prolonged or recurrent symptoms due to delayed or improper treatment, which could lead to pneumonia. However, progression to pneumonia is very rare.

How to treat pneumonia in respiratory tract infections?

For pneumonia caused by bacteria, viruses, parasites, or other pathogens, anti-infection therapy is the core treatment. Antibacterial treatment for bacterial pneumonia should begin as early as possible—antibiotics should be administered immediately upon suspicion of pneumonia. Initial treatment is primarily empirical, and microbial culture-guided therapy may be used when necessary.

Patients with pneumonia should rest in bed, supplement nutrition with high-quality protein, fiber, and calorie-rich foods, and drink plenty of water to promote the elimination of metabolic waste and aid recovery. Symptomatic treatments include expectorants, cough suppressants, correcting fluid and electrolyte imbalances, and oxygen therapy.

DIET & LIFESTYLE

What should patients with respiratory infections pay attention to in daily life?

• Get plenty of rest and ensure adequate sleep.
• Drink more water.
• Monitor body temperature. During the fever stage, chills and shivering may occur—keep warm at this time. During the cooling stage, you may feel hot and sweat—reduce clothing or blankets and avoid overheating.
• Pay attention to coughing up phlegm and avoid using cough suppressants blindly. Follow your doctor's guidance for medication.
• If recovering at home, seek medical attention promptly if symptoms do not improve after three days of medication, existing symptoms worsen, or new symptoms appear.

What should patients with respiratory infections pay attention to in their diet?

Consume high-calorie, protein-rich, and easily digestible foods such as rice, noodles, poultry, fish, and fruit juices.

If throat pain makes eating difficult, opt for soft, liquid-based foods like porridge, noodles, wontons, or fruit juices. Avoid skipping meals, as it may hinder recovery.

In respiratory infections, is it harmful if phlegm is accidentally swallowed?

Generally, no.

The human body has strong resistance to external pathogens. Even if swallowed phlegm contains germs, stomach acid kills most pathogens. Any small amount entering the bloodstream will be eliminated by immune cells.

However, since phlegm from upper respiratory infections often carries many pathogens, it's best not to swallow it.

PREVENTION

How to Prevent Respiratory Infections?

• Frequent handwashing is the best way to prevent respiratory infections.
• Ensure children receive vaccinations on schedule, such as measles, whooping cough, and rubella vaccines, which effectively boost immunity against these respiratory infections and help curb their spread in communities.
• Additionally, strengthening immunity can reduce the risk of respiratory infections. Measures include regular moderate exercise, adequate sleep, and a balanced diet.
• Respiratory infections are more common in winter and spring. The elderly, young children, and those with weakened immunity should take extra precautions, such as avoiding crowded public spaces.
• Quit smoking and avoid exposure to secondhand smoke.