The Difference Between Cold and Flu

Colds and flu share many of the same symptoms, and it can sometimes be difficult (or even impossible) to tell them apart based on symptoms alone. Even the stages of flu recovery are similar to the stages of recovery for the common cold.

Typically, influenza (flu) is worse with symptoms developing more intensely and abruptly. But that's not always the case. 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.

This article looks at the ways that colds and flu differ in not only their causes and symptoms but also in the way that they are diagnosed, treated, and prevented.

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 (often described as "like being hit by a truck").

And, while colds can make you feel pretty miserable, the symptoms are usually not severe enough to "knock you out" in the way that flu can.

Moreover, colds generally do not lead to complications, while flu can sometimes lead to severe and even life-threatening complications—particularly in older adults, pregnant people, children under two, people with chronic lung disease, and those who are immunocompromised.

The differences in symptoms of colds versus flu can be broadly described 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 of Cold vs. Flu

Both the common cold and influenza are caused by respiratory viruses. And both are spread through the airborne droplets produced by coughing and sneezing and 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

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.

Cold symptoms develop as a result of the body's response to the virus—in the form of inflammation—rather than any damage caused by the virus to respiratory tissues.

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 of Cold vs. Flu

In the simplest terms, there are tests that can detect influenza (albeit with varying degrees of accuracy) and none to 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 and Prevention of Colds vs. Flu

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.

Colds are prevented by standard precautions such as frequent hand washing, covering coughs and sneezes, and avoiding close contact with sick people.

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:

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

Flu can be also 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 six months.

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.