Cold and Flu: Symptoms, Causes, Treatment, and More

Colds and flu share many of the same symptoms, including cough, sore throat, and fatigue. Even the stages of flu recovery are similar to the stages of recovery for the common cold. At times, testing may be the only way to determine if the flu is involved so that antiviral drugs—which work for flu but not colds—can be prescribed.

Typically, influenza (flu) is worse with symptoms developing more intensely and abruptly, but not always. Although it can sometimes be difficult (or even impossible) to tell them apart based on symptoms alone, cold and flu have different causes and respond to different treatments.

Cold vs. Flu Symptoms

If you were to broadly characterize colds versus flu, cold symptoms tend to develop gradually while flu symptoms usually develop abruptly. Flu symptoms also tend to be more severe.

Colds generally do not lead to complications, although ear infection is among them. Flu, on the other hand, can sometimes lead to severe and even life-threatening complications—particularly in these populations:

• Older adults
• Pregnant people
• Children under two
• People with chronic lung disease
• Immunocompromised, such as with human immunodeficiency virus (HIV) 

The Centers for Disease Control and Prevention describes the differences in symptoms of colds versus flu as follows:

Cold symptoms typically last between seven and 10 days. Uncomplicated flu also typically resolves within seven days for the majority of people.

Causes

Both the common cold and influenza are caused by respiratory viruses. Both also are spread through the airborne droplets produced by coughing and sneezing, and through contact with saliva or nasal secretions.

Beyond that, the viruses that cause colds and flu differ entirely. This includes the way that they cause illness.

Common Cold

The common cold is caused by one of over 200 respiratory viruses, including:

• Rhinoviruses (most common)
• Respiratory syncytial virus
• Parainfluenza viruses
• Adenoviruses
• Coronaviruses
• Human metapneumovirus

Cold symptoms develop as a result of the body's response to the virus—in the form of inflammation. Symptoms develop when the virus attaches to cellular receptors on the lining of nasal passages and the pharynx (throat). Initial symptoms include a runny nose and sore throat. As the infection progresses, coughing, sneezing, and stuffiness commonly develop.

Influenza

The flu is caused by the influenza virus. There are two main types—influenza A and influenza B—as well as numerous strains that develop seasonally as the virus spreads through populations and mutates.

Unlike cold viruses, influenza attaches to receptors in the trachea (windpipe) and bronchi (the two large airways of the lungs). While inflammation contributes to the symptoms, the virus causes actual damage to respiratory tissues as it replicates.

This accounts for the severity of flu symptoms and the higher risk of flu complications.

Diagnosis

There are some differences in how colds and flu are diagnosed. While there are tests that can detect influenza (with varying degrees of accuracy), none can detect the common cold.

Common Cold

The common cold is diagnosed based on your symptoms and a physical exam. There are no tests to diagnose colds as there are so many causes. If testing is done, it is usually to rule out other possible causes, such as COVID-19.

Influenza

Flu can often be diagnosed by symptoms alone. Even so, it may be well worth seeing a healthcare provider to get a rapid flu test. This is an in-office test that can detect influenza with a swab of your throat or nasal passage. Results are returned within 15 minutes.

If the test result is positive (meaning you have influenza), you may be prescribed treatments to reduce the severity and duration of your illness. If the result is negative, additional testing may be done to ensure you don't have another potentially more serious infection or illness.

Treatment

The only true "cure" for colds and flu is time. There are no drugs that can stop the infection or fully eradicate cold or flu viruses. The immune system will almost invariably bring the infection under control. Your part in treatment is managing symptoms until you feel better.

Common Cold

There is no vaccine, treatment, or medication available to prevent or cure cold viruses. The Centers for Disease Control and Prevention (CDC) advises the following approach if you do get a cold:

• Get plenty of rest.
• Drink plenty of fluids,
• Use an over-the-counter (OTC) pain reliever like Tylenol (acetaminophen) or Advil (ibuprofen), if needed, to ease body aches or fever.

In most cases, people get better on their own.

Influenza

With uncomplicated flu, all you usually need to recover is rest and plenty of fluids. OTC pain relievers, decongestants, expectorants, and cough suppressants may be used if needed.

There are also four antiviral drugs that may lessen flu symptoms and shorten the time you are sick by one to two days if started within 24 to 48 hours of the first signs of infection. They include:

• Rapivab (peramivir)
• Relenza (zanamivir)
  
• Tamiflu (oseltamivir)
• Xofluza (baloxavir)

Prevention

Colds are prevented by standard precautions such as frequent hand washing, covering coughs and sneezes, and avoiding close contact with sick people. Wait to be fever-free for 24 hours before returning to work or school.

Flu also can be prevented with the same standard precautions used for colds, but the best protection by far is getting the annual flu shot or nasal flu vaccine in September or October before flu season begins. Annual vaccination is recommended for all people over the age of 6 months.

When to See a Healthcare Provider

Rest, home remedies (like vaporizer use), and over-the-counter medications often help to relieve cold and flu symptoms as people recover on their own. You may need to see a healthcare provider if you experience more serious symptoms, such as:

• Fever that persists for more than five days
• Nausea
• Vomiting
• Wheezing or shortness of breath
• Trouble swallowing due to sore throat

You also may want to consider seeking a diagnosis if your symptoms suggest another condition, such as a sinus infection, is at work.

Summary

Cold and flu are caused by different respiratory viruses. The common cold tends to start gradually with milder symptoms. Influenza (flu) usually starts abruptly with symptoms like fever and chills that are uncommon with colds.

There are no tests, vaccines, or antiviral treatments specific to the common cold. By contrast, rapid tests, vaccines, and antivirals are available for the diagnosis, prevention, and treatment of flu. Talk to your healthcare provider if your symptoms persist or you need guidance on treatment.