What Causes Upper Respiratory Infection?

An upper respiratory infection, or URI, is a virus and bacteria that infect your respiratory tract above your vocal cords. Symptoms might include a runny or stuffy nose, sore throat, or headache. Common colds, strep throat, and sinus infections are all frequent examples of upper respiratory infections. Most URIs are caused by a virus and go away on their own.

What is an Upper Respiratory Tract Infection?

An upper respiratory infection, or URI, is a viral or bacterial illness in the upper part of your respiratory system. This usually includes your nose, sinuses, and throat.

A runny nose, sore throat, headache, and other cold-like symptoms may come to mind when you think of an upper respiratory infection. Indeed, common colds and other viruses are usually to blame for URIs. But some URIs, such as strep throat or some cases of sinusitis, are bacterial infections. Even others, like the viruses responsible for the flu, COVID-19, and RSV, will cause both upper and lower respiratory infections.

Symptoms and Causes

The symptoms of upper respiratory infections depend on the cause and what part of your body is affected. An infection can lead to swelling in a part of your respiratory tract, causing conditions like pharyngitis, laryngitis, and epiglottitis, which may have different symptoms.

Some symptoms of upper respiratory infections can include:

Cough.
Fever.
Sore throat.
Runny or stuffy nose.
Fatigue.
Sneezing.
Hoarse voice or loss of voice.
Facial pain.
Wheezing.
Swollen lymph nodes.

What Causes an Upper Respiratory Tract Infection

Viruses cause most upper respiratory infections. But bacteria and even fungi can also cause them. Specific causes might include:

Common cold viruses.
Influenza A and B viruses, or the flu.
SARS-CoV-2 virus, or COVID-19.
Respiratory syncytial virus, or RSV.
Varicella-zoster virus.
Herpes simplex virus.
Streptococcus bacteria, like group A strep and Streptococcus pneumoniae.
Haemophilus influenza bacteria.
Moraxella catarrhalis bacteria.
Aspergillus, mucormycetes, and other types of fungi.

Are Upper Respiratory Infections Contagious?

Yes, the viruses and bacteria that cause upper respiratory infections are contagious and spread from person to person. They can spread through:

Respiratory droplets when someone coughs, sneezes, or talks.
Sharing eating or drinking utensils, like forks, spoons, cups, or water bottles.
Contact with objects or surfaces with germs on them, such as doorknobs, light switches, phones, or toys.

Fungi that cause upper respiratory infections are not contagious.

What are the Complications of Upper Respiratory Tract Infections?

Upper respiratory infections such as a cold rarely lead to complications. But URI can sometimes cause inflammation in your lungs, leading to pneumonia. Additionally, if bacterial or fungal infections are left untreated, they can easily travel to other parts of your body and cause:

Meningitis.
Rheumatic fever.
Organ damage.
Scarlet fever.
Sepsis.

You could be at higher risk for complications from a URI if you have either certain health conditions or a compromised immune system, or if you are older than sixty-five. Newborns can also be at a higher risk for severe illness.

How Long Are You Contagious with an Upper Respiratory Infection?

Upper respiratory infections caused by viruses are usually most contagious in the first few days of symptoms. But you might still be contagious even when you start to feel better, especially if you still have symptoms. Strep throat can actually be contagious for weeks if left untreated.