Overview
Infectious diseases caused by pathogens invading the terminal airways, lung parenchyma and interstitium, the main symptoms include cough, sputum, fever, dyspnea, etc. They can be caused by viral, bacterial, fungal and other pathogens, most of which are treated comprehensively, and anti-infective treatment is the key.
Definition
Lung infection refers to infectious diseases caused by invasion of end airways, lung parenchyma and lung interstitium by pathogens such as bacteria, viruses, fungi, parasites, etc., and is a collective term for a group of diseases [1-2].
Lung infections are mostly manifested as pneumonia, but are not fully equivalent to pneumonia.
In addition to pathogenic infections, physical and chemical factors, drugs and other factors can also cause pneumonia [1], but the latter is not a lung infection.
Although tuberculosis and lung abscess are also pathogenic infections of the lungs that cause disease, people often do not include them in the category of pneumonia.
Classification
Lung infections can usually be categorized as follows, depending on the pathogen [1].
Bacterial pneumonia
Pneumonia caused by bacterial infections such as Streptococcus pneumoniae, Staphylococcus aureus, Streptococcus aureus, Streptococcus haemolyticus A, and Klebsiella pneumoniae.
Pneumonia caused by atypical pathogens
Pneumonia caused by pathogens such as Legionella, Mycoplasma and Chlamydia.
Viral Pneumonia
Pneumonia caused by viruses such as coronavirus, adenovirus, respiratory syncytial virus and influenza virus.
Lung fungal disease
Such as Candida, Aspergillus, Cryptococcus, Pneumocystis, and other lung diseases.
Pneumonia caused by other pathogens
Such as pneumonia caused by Rickettsia, Toxoplasma gondii (e.g. Toxoplasma gondii), parasites (e.g. Pneumocystis carinii, Schistosoma pneumoniae, Schistosoma pneumoniae).
Morbidity
Lung infections are diseases with high morbidity and total morbidity and mortality in the world, and according to statistics, lung infections were the fourth leading cause of death in the world in 2019, leading to 2.6 million lives in 2019 and 3.06 million deaths in 2000 [3].
There is no comprehensive authoritative data on the incidence of lung infections.
Etiology
Causes of disease
Types of pathogens
Lung infections are caused by pathogens that invade the lungs, most commonly bacteria, but can also be caused by viruses, atypical pathogens, fungi, and parasites.
Pathogens invade the lungs through
Pathogens can enter the lungs and multiply in the lungs through inhalation, hematogenous dissemination, spread of neighboring infected sites, and aspiration of colonizing bacteria from the upper respiratory tract.
Susceptible groups
Elderly, infants and young children, immunocompromised, long-term bedridden people, etc.
Triggering factors
Rain, cold, sudden change of climate, overwork, etc. can reduce the local defense function of the respiratory tract and the immune function of the human body, resulting in the smooth invasion and reproduction of various pathogens.
Pathogenesis
Whether or not the disease develops after exposure to pathogens depends on the number and virulence of pathogenic pathogens on the one hand, and the resistance of the body on the other.
Under normal circumstances, the normal function of the mucosa and cilia in the bronchial tubes and the normal function of cellular defense together constitute the immune defense system of the respiratory tract. Although daily exposure to a variety of pathogens invasion, but the body can be effective defense, the formation of a kind of “invasion and defense” between the balance, will not easily occur in the lung infection.
When the invasive ability of pathogens increases significantly, such as invading pathogenic microorganisms in large numbers and with high virulence, or when the body’s defense function decreases, such as impaired respiratory defense function and decreased systemic immune function, the balance between invasion and defense mentioned above is disturbed, and then lung infections will easily occur.
Symptoms
Main Symptoms
Symptoms vary depending on the type of pathogen and the severity of the lung infection, but they are mainly respiratory symptoms and may be accompanied by systemic symptoms.
Cough
The cough may be paroxysmal and irritating, and in severe cases, the cough is persistent and severe, which may interfere with sleep.
Coughing up sputum
The color of sputum varies according to the pathogen.
For example, rusty sputum may be a Streptococcus pneumoniae infection, and reddish brown jelly-like sputum may be a Klebsiella pneumoniae infection.
It may also present as bloody sputum or hemoptysis.
Dyspnea
When there is a massive lung infection, it will lead to dyspnea, which is characterized by breathlessness, chest tightness, shallow and fast breathing, etc. Severe oxygen deprivation can lead to bruising of lips and fingernails, or even death.
Chest pain
For example, Streptococcus pneumonia can lead to chest pain on the affected side.
Systemic symptoms
May manifest as fever, chills, chills, malaise, loss of appetite, muscle aches and pains.
Complications
When the lung infection is more serious or untreated, it can lead to a variety of complications, the following are some of the more common complications.
Pleurisy
Lung infection can involve the pleura, causing pleurisy, chest pain, dyspnea and other symptoms.
Pyothorax
Pathogen infection produces purulent exudate into the chest cavity, which can present with symptoms such as high fever and dyspnea.
Lung necrosis and cavitation
Some lung infections can destroy the normal structure of the alveoli and necrosis and cavitation can occur.
Infectious shock
Severe lung infections are prone to infectious shock, especially in the elderly, which is characterized by loss of consciousness, lowered blood pressure, cold extremities, excessive sweating, tachycardia, and cardiac arrhythmia.
Consultation
Department of Medicine
Respiratory Medicine
For symptoms such as cough, sputum, fever, dyspnea, chest pain, etc., it is recommended to consult a respiratory physician.
Emergency Department
When symptoms such as high fever, unconsciousness, irritability, wet and cold limbs, and oliguria occur, it is recommended to go to the Emergency Department immediately, or call 120 for emergency help.
Pediatric Internal Medicine
Children with symptoms such as cough, sputum, fever, difficulty breathing, chest pain, etc. can first go to the Pediatric Internal Medicine Department.
Preparation
Preparing for your visit: registering, preparing your documents, FAQs
Tips
Avoid taking fever-reducing medicines or antibiotics by yourself before going to the doctor, so as not to influence the doctor’s judgment of the condition.
Patients with high fever can first take physical cooling, such as applying cold compresses to the forehead, wiping hands, feet and armpits with warm water, and drinking plenty of water.
Chest X-ray or chest CT is often needed when seeking medical treatment, so avoid wearing clothes made of metal, and those who are pregnant or preparing for pregnancy should inform the doctor in a timely manner.
Preparation Checklist
Symptom list
Pay particular attention to the time of onset of symptoms, special manifestations, etc.
Is there fever? What is the highest temperature?
Is there nasal congestion or runny nose?
Is there a cough? How long has the cough lasted?
Is there any phlegm? What does the phlegm look like?
Are there any aggravating or relieving factors?
Are there any other discomforts?
Medical History Checklist
Any recent exposure to cold or exertion?
Has there been prolonged bed rest?
Has there been any contact with patients with cold or fever before the onset of the illness?
Are there any chronic diseases such as chronic bronchitis or chronic obstructive pulmonary disease?
Any long-term oral glucocorticoid, immunosuppressant or other drugs?
Checklist
Test results in the past six months, which can be brought to the doctor’s office
Laboratory tests: routine blood test, C-reactive protein, calcitoninogen, sputum bacterial culture + drug sensitivity test, influenza + parainfluenza virus nucleic acid, novel coronavirus nucleic acid test.
Imaging tests: Chest X-ray, Chest CT.
Medication List
Medication used in the last 3 months, if available, bring along the box or package for medical consultation
Antibiotics: e.g. penicillin, cefaclor, ceftazidime, roxithromycin, etc.
Antipyretics and analgesics: e.g., ibuprofen, acetaminophen, etc.
Nasal decongestants: e.g. pseudoephedrine nasal drops.
Phlegm-cleansing drugs: e.g., Ambroxol, etc.
Diagnosis
Diagnosis
Generally speaking, the clinical diagnosis can be made based on the patient’s medical history, epidemiologic situation, respiratory and systemic symptoms and signs, combined with laboratory tests, chest X-ray or chest CT examination, and the pathogenetic examination can help to clarify the cause of the disease.
Medical history
The following conditions may be present.
Previous close contact with a person with a confirmed or suspected lung infection.
Long-term use of immunosuppressive drugs and immunodeficiency diseases.
Cold, rain, or excessive fatigue prior to onset of illness.
Poor physical fitness and prolonged bed rest.
Clinical manifestations
There are common symptoms such as cough, sputum, fever and chest pain, which may be accompanied by chills, chest pain, fatigue and poor appetite.
The respiratory rate may increase, and bruising of the lips and mouth may occur; bronchial breath sounds and wet rales may be heard in the chest on physical examination.
Laboratory tests
Sputum culture, blood routine, C-reactive protein, calcitoninogen, blood biochemistry, chest radiograph, chest CT, etc., are usually required, and bronchoscopy may be performed if necessary.
Diagnostic Criteria
Lung infection is a collective term for various infections of the lungs. The diagnostic criteria for different diseases are not exactly the same, and can be found in the entries for each disease.
Differential diagnosis
The symptoms and manifestations of many diseases are similar to those of lung infections, such as tuberculosis, lung cancer, pulmonary embolism, etc., which often need to be differentiated.
Tuberculosis
Similarities: Fever, fatigue, cough and other symptoms may occur.
Differences: Tuberculosis has a slow and gradual onset, with a longer course, low-grade fever in the afternoon, accompanied by night sweats, weight loss, insomnia and other symptoms; it can be differentiated from Mycobacterium tuberculosis by the detection of Mycobacterium avium on antacid bacillus smear, Mycobacterium avium culture, and nucleic acid test.
Pulmonary embolism
Similarity: both may have symptoms such as dyspnea and hemoptysis.
Differences: People with pulmonary embolism often have a history of trauma, surgery, tumor, and lower extremity venous thrombosis; elevated D-dimer can reveal a tendency to thrombosis; CT pulmonary arteriography, radionuclide lung ventilation/perfusion scanning, and MRI can help to differentiate.
Lung cancer
Similarities: both may present with prolonged cough, fever and sputum.
Differences: Lung cancer often occurs in people who have smoked for a long time and are of advanced age; it may also present with chest pain and hemoptysis. Imaging examination can find nodules, enlarged hilar lymph nodes and other changes; sputum exfoliative cells and histopathological examination can find malignant tumor cells, which can lead to a clear diagnosis.
Treatment
Treatment purpose: cure the disease, control or relieve the symptoms, and prevent complications [4].
Therapeutic principle: lung infections need to be treated comprehensively according to the different pathogens, choosing appropriate anti-infective drugs when necessary, and giving symptomatic treatment at the same time [5].
Drug treatment
The treatment of lung infection is mainly to relieve symptoms, control disease progression, prevent and reduce complications. Among them, anti-infective treatment is the key treatment for lung infection [6].
Antimicrobial drugs
When the pathogen species is unknown, antimicrobial drug therapy can be selected empirically first. When the pathogen species is clear, whether to change drugs can be considered according to the results of drug sensitivity test.
Taking patients with pneumonia as an example, considering that Streptococcus pneumoniae pneumonia is the most common, penicillin treatment is preferred based on the premise that patients are not allergic to penicillin before the pathogen is not clear. If allergic to penicillin, drugs such as cefotaxime or ceftriaxone can be changed.
When the sputum culture is clear of the pathogen, the decision to adjust antimicrobials can be made in conjunction with drug sensitivity testing.
If it is streptococcal infection but resistant to penicillin, cefotaxime or ceftriaxone can be used; fluoroquinolones such as norfloxacin and levofloxacin can also be used.
For staphylococcal infections, penicillinase-resistant semisynthetic penicillins, such as benzathine sodium, can be used; cephalosporins, such as cefuroxime sodium, can also be used.
Antiviral drugs
Not all viral infections require antiviral treatment.
If necessary, therapeutic drugs are selected according to the different viruses, e.g. acyclovir is used for herpes virus and chickenpox virus infections; ganciclovir is used to treat cytomegalovirus infections.
Antifungal drugs
Anti-fungal drugs can be prescribed for fungal infections of the lungs.
Antifungal drugs include fluconazole, itraconazole, voriconazole and posaconazole.
Other medications
For persistent fever with temperature over 38.5℃, antipyretic drugs such as ibuprofen, acetaminophen, and loxoprofen can be used.
People with nasal congestion can use drugs to reduce nasal mucosal congestion and antihistamines, such as pseudoephedrine hydrochloride, chlorpheniramine and so on.
For cough and phlegm, cough expectorants can be used, such as compound licorice combination, ambroxol and so on.
Glucocorticosteroids are not routinely used for lung infections, but glucocorticosteroids are commonly used and effective drugs for organic pneumonia caused by lung infections.
Pneumonia has more common symptoms in TCM, and TCM treatment can be considered when necessary [7].
Surgical treatment
In case of abscess chest formed by lung infection, puncture and drainage can be performed, and thoracoscopic surgery or traditional surgery can be performed if necessary.
Other treatments
Keep the airway open, give oxygen to those with respiratory distress and hypoxia manifestation, and according to the severity of hypoxia, choose conventional oxygen therapy, transnasal high-flow oxygen therapy, non-invasive ventilation or invasive mechanical ventilation, etc., and use extracorporeal membrane oxygenation if necessary.
Nutritional support should be given to those who cannot eat.
Prognosis
Cure
A small percentage of people with lung infections heal spontaneously.
Most patients with pulmonary infections resolve effectively with treatment, but some patients of advanced age, with underlying disease, and with multidrug-resistant bacterial infections may develop complications or have a poor prognosis.
Prognostic factors
Alcoholism, smoking, advanced age, and immunosuppressed status can lead to a worse prognosis.
Hazardous
Work and life can be affected by severe symptoms such as cough and fever.
Viral infections can be spread by droplet transmission and may be contagious.
With underlying diseases, such as chronic obstructive pulmonary disease, heart failure, asthma, etc., acute exacerbation may be induced by lung infection.
In severe cases, the disease may lead to death of the patient.
Daily
Daily Management
Daily management
Certain lung infections are contagious and patients should wear masks and cover their mouths and noses when coughing to prevent causing transmission. Children, the elderly, pregnant women and other immunocompromised people should avoid close contact with the patient.
When you are seriously ill, you should rest in bed and gradually resume activities when your condition improves. When you have a fever, you can use lukewarm water baths and cold compresses to help lower your body temperature, and measure your body temperature regularly.
Maintain a good work routine, ensure sufficient sleep time, avoid exertion and staying up late.
Ventilate the room, and keep the temperature and humidity at a suitable level to minimize cold air stimulation and prevent cold.
If you already have high blood pressure, diabetes and other diseases, you need to follow the doctor’s requirements, the full amount of regular medication, and follow up on time, do not stop taking medication on your own because of symptomatic relief, to avoid relapse.
Diet management
Pay attention to the nutritional balance of the diet, the diet should be light, more protein, vegetables, fruits [8].
Avoid excessive alcohol consumption.
Drink adequate amount of water, 7 to 8 glasses (1500 to 1700 ml) per day for adults, advocate drinking plain water, do not drink or drink less sugary drinks.
Smoking cessation
Quit smoking and avoid exposure to “second-hand smoke”.
Disease monitoring
Observe changes in body temperature when fever develops.
Observe whether symptoms such as coughing decrease.
When coughing up sputum, observe the color, smell and amount of sputum.
Follow-up and review
After two weeks of discharge, repeat blood tests, chest X-ray or chest CT to check for changes in condition and recovery.
If symptoms worsen or new symptoms appear, consult a doctor.
Prevention
The following measures will not eliminate the occurrence of lung infections, but will reduce the risk of lung infections.
Wear a mask when going out and avoid crowds.
Wash your hands frequently and do not share cups and utensils with others [9].
Moderate exercise can be carried out according to one’s own situation, and it is recommended to carry out more aerobic exercise such as jogging, swimming, brisk walking, yoga, square dancing, etc. to improve physical fitness.
Vaccination.
Influenza season can be prevented by influenza vaccination [10].
Pneumonia vaccination is available for those older than 65 years of age, or those with cardiovascular disease, pulmonary disease, diabetes, alcoholism, cirrhosis, and immunosuppression.
Neocoronavirus vaccination reduces neocoronavirus infection and morbidity.
Neonatal BCG vaccination helps to control tuberculosis [11].
For those who are bedridden for long periods of time, chaperones should assist in turning and patting the back, adjusting posture appropriately, and taking special care to avoid choking when eating.