Upper Respiratory Tract Infection (URTI)

An upper respiratory tract infection (URTI) is a viral or bacterial illness in the upper part of your respiratory system, which includes your nose, sinuses and throat. The upper portion of your respiratory system is susceptible to many bacteria and viruses that can cause a range of symptoms. They can easily spread by being in contact with other people, and are often transferred by sneezing or coughing.

URTIs are among the most common reasons people see a doctor worldwide, and while the great majority are mild and resolve on their own, they remain a leading cause of missed school and work days simply because of how frequently they occur and how easily they spread in shared spaces.

Understanding the Upper Respiratory Tract

The respiratory system is generally divided into an upper and lower portion. The upper respiratory tract includes the nose, sinuses, pharynx (throat) and larynx (voice box) — essentially everything from the nostrils down to just above the vocal cords. The lower respiratory tract, by contrast, includes the trachea (windpipe), bronchi and lungs.

This distinction matters clinically. Infections confined to the upper respiratory tract, while uncomfortable, are generally milder and self-limiting, whereas an infection that spreads or begins in the lower respiratory tract — such as bronchitis or pneumonia — tends to affect breathing more significantly and is more likely to require closer medical attention. Recognising which symptoms point to the upper tract, and which suggest the infection may be moving lower, is part of how doctors decide how a respiratory illness should be managed.

What Is an Upper Respiratory Tract Infection?

The most common URTI is the common cold. Other types of URTIs include sinusitis, rhinitis, laryngitis and pharyngitis, each affecting a slightly different part of the upper respiratory tract and producing a somewhat different pattern of symptoms.

Common Cold: The most frequent type of URTI, typically causing a runny or blocked nose, sneezing and a mild sore throat. It is caused by any of over 200 different viruses and usually resolves on its own within about a week.
Sinusitis: An infection or inflammation of the sinuses, the air-filled spaces within the bones of the face. It causes facial pain or pressure, nasal congestion and thick nasal discharge, and can be triggered by a preceding viral cold that allows bacteria to take hold in blocked, mucus-filled sinuses.
Rhinitis: Inflammation of the lining of the nasal passages, causing a blocked or runny nose and sneezing. It can result from a viral infection, but can also be triggered by allergies, in which case it is not infectious at all.
Laryngitis: An infection or inflammation of the voice box (larynx) and vocal cords, typically causing hoarseness or a temporary loss of voice, along with a dry or scratchy throat.
Pharyngitis: Also known as a "sore throat," pharyngitis affects the back of the throat (the pharynx) and is usually caused by a virus, though a bacterial cause, most notably group A streptococcus, is responsible for a meaningful proportion of cases, particularly in children.

Symptoms of URTI

If you are suffering from a URTI, some common symptoms you may experience include:

Fever: A fever reflects the body's immune response to infection and is generally more pronounced with influenza or bacterial URTIs than with an ordinary cold.
Cough: Coughing is the body's way of clearing irritation or excess mucus from the throat and airways, and can persist for one to two weeks even after other symptoms improve.
Phlegm: Mucus production increases as the body attempts to trap and clear viruses or bacteria and the irritated tissue lining the airway.
Sneezing, runny or blocked nose: Inflammation of the nasal lining causes increased mucus production and sneezing as the body attempts to expel the irritant or infection.
Body aches: The body's immune response to infection commonly causes generalised muscle and joint discomfort, often one of the earliest symptoms felt.
Headaches: Sinus congestion and pressure, along with the general inflammatory response to infection, frequently produce headaches during a URTI.
Swollen lymph nodes: Lymph nodes in the neck often enlarge and become tender as the immune system actively responds to the nearby infection in the nose or throat.
Loss of appetite: Feeling unwell and the body's redirection of energy toward fighting infection commonly reduces appetite during an acute illness.
Fatigue: The immune response to infection is metabolically demanding, which commonly produces a pervasive sense of tiredness until the illness resolves.
Sore throat: Inflammation and irritation of the throat lining, sometimes combined with post-nasal drip, commonly produces a scratchy or painful sore throat.

Causes of URTI

URTI is caused by viruses or bacteria that infect the nose and throat. You may catch a URTI if you:

Viral infections: Most upper respiratory tract infections (URTIs) are caused by viruses that infect the nose, throat and upper airways. Common viruses include rhinovirus, influenza virus, parainfluenza virus and coronavirus. Most common colds, in particular, are viral infections.
Bacterial infections: Bacteria are a less common cause of URTIs overall but can cause certain infections. For example, Streptococcus bacteria can cause strep throat, while some cases of sinusitis may become bacterial after an initial viral infection.
Respiratory droplets from an infected person: URTIs can spread when an infected person coughs, sneezes or otherwise releases respiratory droplets containing viruses or bacteria into the air. Being in close proximity to someone who is infected can increase the chance of inhaling these droplets.
Contact with contaminated surfaces: Some viruses that cause URTIs can survive on surfaces for a period of time. Touching an object contaminated with infectious particles and then touching your nose, mouth or eyes before washing your hands can allow the infection to enter your body.
Close contact with infected people: Spending time around someone with a URTI, particularly in crowded or enclosed spaces, can increase your exposure to infectious respiratory particles. Good hand hygiene and avoiding close contact with people who are unwell can help reduce the risk of infection.

Knowing whether a URTI is viral or bacterial is important because antibiotics only work against bacterial infections. They do not treat viral infections, which account for the majority of URTIs.

Risk Factors of URTI

Anyone can get sick from URTI but some have a higher risk than others. Factors include:

Age: Older adults and young children are at a higher risk of URTI. Young children have immune systems still being trained through repeated exposure to new viruses, while older adults may have a less robust immune response, making both groups more susceptible to frequent or more severe infections.
Existing medical conditions: People with weakened immune systems, disabilities, and pregnant women are more likely to develop URTI, as a reduced or altered immune response makes it harder for the body to fight off common respiratory viruses and bacteria before they cause symptoms.
Crowded environments: Schools, childcare centres, offices and public transport bring people into close, prolonged contact, creating ideal conditions for respiratory viruses to spread from person to person.
Smoking: Smoking damages the protective lining of the respiratory tract and impairs the tiny hair-like structures that normally help clear mucus and irritants, making smokers more susceptible to frequent or prolonged URTIs.
Seasonal factors: Many common respiratory viruses circulate more actively during certain periods of the year, such as periods of heavy rainfall or increased indoor crowding with air conditioning, which is part of why URTIs tend to cluster at certain times.

Possible Complications of URTI

While most URTIs are mild and resolve without incident, certain symptoms can signal that the infection has become more serious or has spread beyond the upper respiratory tract, including high fever, difficulty breathing, chest pain, wheezing, dizziness, visible retractions of the chest wall with breathing, or confusion.

Secondary bacterial infection: An initial viral URTI can sometimes weaken the lining of the nose, sinuses or throat enough to allow a secondary bacterial infection to take hold, which may require antibiotic treatment where a purely viral infection would not.
Progression to the lower respiratory tract: Occasionally, an upper respiratory infection can progress or spread into the lower respiratory tract, resulting in bronchitis or pneumonia, which affect breathing more significantly and generally require closer medical evaluation.
Middle ear infection: In children particularly, the short, horizontal shape of the Eustachian tube makes it easier for a URTI to spread from the throat into the middle ear, causing a painful ear infection.
Sinusitis or asthma flare-ups: A common cold or other URTI can trigger a flare-up of pre-existing sinus disease, or, in those with asthma, can trigger a worsening of asthma symptoms requiring adjustment of usual asthma treatment.

These complications remain relatively uncommon overall, but they are part of why any URTI accompanied by high fever, breathing difficulty, chest pain, or symptoms that are worsening rather than improving after the first several days is generally worth having assessed.

How URTI is diagnosed

Medical history and symptom assessment: Your healthcare provider will ask about your symptoms, when they started and whether they have been getting better or worse. They may also ask about recent contact with someone who was unwell, your medical history and any underlying conditions that could affect your risk of complications.
Physical examination: Your healthcare provider may examine your nose, throat, ears and sinuses for signs of infection or inflammation. They may also listen to your lungs for abnormal breath sounds and check your temperature, heart rate and oxygen levels when appropriate.
Rapid throat swab for bacterial infections: If you have symptoms suggesting strep throat, a rapid throat swab may be performed to check for Streptococcus bacteria. A laboratory throat culture or molecular test may sometimes be used when further confirmation is needed.
Nasal or throat swabs for respiratory viruses: A nasal or throat swab may be recommended when identifying a specific virus would affect treatment or infection-control measures. Depending on the test, it may detect viruses such as influenza, respiratory syncytial virus (RSV) or COVID-19.
Chest X-ray when a lower respiratory infection is suspected: A chest X-ray is not routinely needed for an uncomplicated URTI. It may be recommended if there are symptoms or examination findings suggesting that the infection has spread to the lungs or that pneumonia may be present, such as persistent breathing difficulties, low oxygen levels or abnormal lung sounds.
Further tests for persistent or severe symptoms: If symptoms are unusually severe, prolonged or associated with complications, your healthcare provider may recommend additional investigations based on your symptoms and medical history. These may include blood tests or other imaging to look for complications or alternative causes of the symptoms.

Preventing URTI

You can reduce your risk of getting or spreading upper respiratory infections by:

Staying up to date on all recommended vaccinations: Vaccines such as the annual influenza vaccine reduce the likelihood of infection with some of the more significant viruses responsible for URTI, and can also reduce the severity of illness if infection does occur.
Washing your hands frequently: Regular handwashing, particularly after being in public spaces or before touching your face, removes viruses picked up from surfaces before they have a chance to enter the nose, mouth or eyes.
Disinfecting surfaces: Regularly cleaning frequently touched surfaces, such as door handles, phones and shared office equipment, reduces the chance of viruses surviving on surfaces long enough to be picked up by someone else.
Wearing a mask around people if you are sick: Wearing a mask when you are unwell reduces the spread of respiratory droplets to those around you, particularly in enclosed or crowded spaces.