What is a chest infection?
A chest infection usually refers to an infection of the lower respiratory tract (trachea, bronchi) and/or lungs. The term chest infection can be misleading. Firstly the lower respiratory tract and lungs are not the only organs in the chest. Secondly the term is sometimes incorrectly used to refer to other non-infectious respiratory conditions that may worsen or persist after an infection.
Therefore a chest infection should be understood to refer to a lower respiratory tract infection (tracheitis and/or bronchitis) and/or pneumonia (lungs). It may also sometimes be used to the describe an infection of the lining around the lungs (pleura ~ pleuritis). When organs like the heart or the lining around the heart (pericardium) become infected, these conditions are usually not encompassed within the term chest infection.
Is the cold or flu a chest infection?
The flu (seasonal influenza) is a viral infection that can affect the entire respiratory tract, from the nose all the way down to the lungs. When the trachea, bronchi and/or lungs are involved then the flu is technically a chest infection. However, most people with healthy immune systems do not have a severe lower respiratory tract infection with the flu.
The common cold on the other hands usually affects only the upper respiratory tract like the nose and throat. It is therefore not a chest infection although secondary infections can follow the cold and affect the trachea, bronchi and/or lungs. In these cases the secondary infection would be referred to as a chest infection.
Can a chest infection be deadly?
Chest infections can be serious and potentially life-threatening. It depends on the causative infectious agent, severity of the infection, immune defenses and any pre-existing conditions. For example, elderly people are at a greater risk of serious complications and even death from a chest infection, as are people who have a weakened immune system such as people with AIDS or those on certain immune-suppressing treatments.
This does not mean that every severe chest infection in people who are immune compromised will lead to fatal outcomes. However, the risk of complications and even death is greater in these individuals particularly when treatment is delayed. As a general rule, every chest infection even in healthy individuals should be assessed and treated by a medical professional, particularly if it is severe, persisting or worsening.
Read more on pneumonia.
Symptoms of a Chest Infection
Irrespective of the area that is most affected, the same respiratory symptoms appears in most cases of tracheitis, bronchitis and pneumonia. This includes:
- Cough – dry (non-productive) or wet (productive)
- Shortness of breath or even difficulty breathing
- Rapid, shallow breathing or slow, deep breathing
- Hoarse voice or whispery tone
- Chest pain and discomfort
- Abnormal breathing sounds – wheeze, rhonchi, crackles
In addition there may be additional symptoms such as fatigue, malaise (feeling of being unwell) and fever. In severe or prolonged infections there may also be symptoms like unintentional weight loss.
Causes of Chest Infections
Most chest infections are due to viruses or bacteria but fungi and even protozoa (single-celled parasites) can also be responsible. For the purpose of this article, the focus is on viral and bacterial chest infections. It is often thought that bacterial chest infections are more severe. Although common viral infections like the flu may cause a mild chest infection, some viruses can cause severe and even deadly chest infections.
A host of different viral and bacterial species can be responsible for chest infections. Some of the pathogens have responsible for a chest infection have been listed below. It is important to note that this is not a complete list of all the possible bacteria and viruses that may cause a chest infection. Some uncommon viruses and bacteria may also cause rare chest infections.
- Adenoviridae ( adenoviruses)
- Coronaviridae (coronaviruses) – SARS, MERS
- Bunyaviridae (arboviruses) – Hantavirus
- Orthomyxoviridae (orthomyxoviruses) – Influenza virus
- Papovaviridae (polyomavirus) – JC virus, BK virus
- Paramyxoviridae (paramyxoviruses) – Parainfluenza virus (PIV), respiratory syncytial virus (RSV), human metapneumovirus (hMPV), measles virus
- Picornaviridae (picornaviruses) – Enteroviruses, coxsackievirus, echovirus, enterovirus 71, rhinovirus
- Reoviridae ( rotavirus)
- Retroviridae (retroviruses)- Human immunodeficiency virus (HIV), human lymphotropic virus type 1 (HTLV-1)
- Acinetobacter baumannii
- Actinomyces israelii
- Bacillus anthracis
- Bordetella pertussis
- Chlamydia pneumoniae
- Coxiella burnetii
- Enterococcus (E faecalis, E faecium)
- Escherichia coli
- Francisella tularensis
- Haemophilus influenzae
- Klebsiella pneumoniae
- Legionella pneumophila
- Moraxella catarrhalis
- Nocardia asteroides
- Pseudomonas aeruginosa
- Streptococcus pneumoniae
- Staphylococcus aureus
- Yersinia pestis
- Mycoplasma pneumoniae
- Mycobacterium tuberculosis
Spread of Chest Infections
Like most respiratory infections, chest infections are spread through respiratory droplets. This includes the mucus and saliva from an infected person that is made airborne due to coughing or sneezing. These infective droplets are the inhaled by a person who is uninfected. It enters the respiratory tract, attaches to the respiratory lining (epithelium) and causes an infection.
Less commonly, certain infectious agents may enter through the mouth with eating contaminated food, drinking contaminated water, sharing eating utensils, mouth-to-mouth contact and hand-to-mouth contact. However, even in these cases the infectious agent is in the secretions from an infected person, such as saliva and respiratory mucus. Although uncommon, bacteria and viruses responsible for chest infections can enter through blood.
Are chest infections contagious?
Most lower respiratory tract infections are highly contagious. This means that it can be easily spread from one person to another. However, some of these infections are only likely to affect people with a weak immune system or with other risk factors. Respiratory droplets can remain airborne for hours in closed rooms. Therefore a chest infection may be spread without making direct contact with an infected person.
Treatment of Chest Infections
Chest infections are treated with the respective antimicrobial agents. Antiviral drugs may be used for viral chest infections while antibiotics are needed for bacterial chest infections. In the rare case of a fungal chest infection, antifungal agents will be necessary.
However, medical treatment is not always necessary. In some viral chest infections, such as the flu, the infection resolves within a few days without any medical treatment other than supportive measures to manage symptoms like fever. Depending on the causative agent, vaccines may be available to prevent certain chest infections.