The Cold and Flu: Understanding the Basic Respiratory Conditions

Learn basic facts about the cold and flu.

As the days get shorter and the weather becomes colder, an old and unwanted pair sneaks back into our lives. We all know that it’s that time of year again when the nasty cold and flu viruses emerge to haunt us. These common respiratory conditions affect millions of individuals annually around the world. However, in this battle against microbes, knowledge is your most excellent defense.

This article will explore the world of colds and flu, including their definitions, causes, symptoms, and effective preventative measures.

What are Cold and Flu?

Colds and flu are viral respiratory infections that are contagious. They primarily impact the upper respiratory system’s nostrils, throat, and airways. Despite having comparable symptoms, both are caused by different types of viruses.

cold and flu microscopic


The common colds (also called viral rhinitis) are mild viral infections that affect the upper respiratory tract. They are one of the most common infections in humans, with adults averaging 2-4 per year and children 6-8, and occur typically during the early autumn and spring.

Colds are neither life-threatening nor severe infections, but their impact is significant. They are contagious, which means they can be transferred from one person to another and have an incubation period of about one to seven days, which is the time of the appearance of symptoms. A cold usually lasts seven to ten days but can last up to two weeks if a particular virus causes it.


Influenza, also known as the flu, is a viral infection of the upper and lower respiratory tract caused by influenza viruses.

The respiratory symptoms of these viruses are typically more severe than those of the common cold. The incubation period for the flu ranges from one to four days and can be spread from person to person. The typical duration of influenza is around five days but can be as long as two weeks in the most severe cases. Most flu outbreaks occur during the winter.

Unlike a common cold, influenza can be fatal in some individuals with compromised health.

Between 12,000 and 50,000 people in the United States die from the flu yearly. And it sends anything from 150.000 to 700.000 people to the hospital annually. In comparison, hospitalization or death due to the common cold is highly unusual.

While influenza is more dangerous than the average cold, it is, fortunately, considerably less prevalent.

Most individuals in the United States suffer from 2-4 colds every year, although only around 8% of the population really gets the flu each year.

The Onset: How Do You Catch a Cold or Flu?

The common cold and flu are highly contagious and can spread through particles in the air emitted when an infected person coughs, sneezes, or speaks. These droplets can then be inhaled by close individuals, causing infection.

These viruses can also be transmitted by contacting surfaces contaminated with cold or flu and touching the face, mouth, nostrils, eyes, or respiratory particles on surfaces like door handles or keyboards. Stainless steel and plastic offer a better environment for virus survival than softer surfaces like cloth and carpet. The duration of virus survival also depends on environmental parameters like temperature, humidity, and droplets.

Upon transmission to a new body, the pathogen enters the respiratory tract of a newly infected person and uses its portion spikes as a key to enter the cell. It then hijacks the nucleus and replicates and spreads the virus later, showing the symptoms in one or two days.

You Seldom Catch the Common Cold and Flu Due to Winters.

Contrary to popular belief, the common cold isn’t associated with extremely cold weather and is a myth.

One factor that has been linked is the cold temperature which allows the viruses to proliferate and survive easily. It is because, during the winter, people are more likely to spend time indoors and near others, breathing in the same environment as an infected person. This causes environments with diminished ventilation, which facilitates the spread of viruses from person to person.

Viruses like influenza typically enter the body through the mouth and nose, but our nasal passages are generally well-defended. However, cold weather reduces our ability to cleanse our sinuses of mucus, making it more straightforward for viruses to infect our bodies as they can travel up to two meters.

That is why if you have a cold and flu and sneeze in a congested area, those nearby may inhale your sneeze particles and contract the virus, not because of cold weather.

Common Viruses Responsible For Cold and Flu

Various viruses, including rhinoviruses, parainfluenza, enteroviruses, and seasonal coronaviruses, can cause the common cold. It is to be told that the seasonal coronaviruses differ from the virus responsible for COVID-19. Approximately 30% to 50% of colds are caused by rhinoviruses. When one of these cold viruses infects a person, it attacks the cells lining the nose and pharynx, causing inflammation and typical cold symptoms.

On the other hand, flu is only caused by two viruses, influenza A and Influenza B.

Symptoms Of Cold and Flu

Everyone experiences a cold or flu differently. Age, general health, and immune system strength can all impact the severity and number of symptoms you experience.

The common cold causes upper respiratory symptoms such as sore throat, blocked or runny nose, post-nasal drip, chest congestion, red and irritated eyes, and persistent cough. Also common are fatigue and general aches and pains, but less common ones include fever

Common cold symptoms typically peak gradually between the second and fourth day of infection and last approximately one week. People are generally contagious as long as they have symptoms, typically for the first 24 hours of illness. Up to 25% of individuals may experience persistent symptoms lasting several weeks.

The degree of flu symptoms and infection varies from one individual to the next and even within the same age group. The influenza virus mainly infects the respiratory system but can also spread to other body parts and make you sick. Typical symptoms consist of:

  • Mild to severe fever (101 to 103 degrees Fahrenheit).
  • Shivering and chills
  • Aching muscles and joints
  • Headaches
  • Fatigue
  • Wheeze
  • Throat pain
  • Runny nose
  • Dizziness
  • Diarrhea and vomiting in case of children

Generally, the flu symptoms typically develop rapidly, peak around the third or fourth day after infection, and can continue anywhere from seven to ten days.


Remember that the flu usually takes about two days to spread. So, if you get a virus on Saturday morning, you might be able to start spreading it to other people by Sunday evening. And by Monday afternoon, you’ll probably start to feel those awful flu-related body aches.

Difference Between Cold and Flu

flu and cold

Is it common cold or flu? You may ask yourself this question when you wake up with a sore throat, runny nose, and cough. While the symptoms of cold and flu are similar, there are several key differences to be aware of.

The following table can be seen for a detailed summary of cold and flu symptoms as per recent data.

Symptoms  Cold Flu
Abrupt onset of symptoms Gradual onset Can occur within 3-6 hours
Fever  Rare Mild to high (100-102 °F), sometimes higher, especially in young children); lasts 3-4 days
Body/muscle aches & pains Occasionally, mild Usual; often severe
Headache Uncommon Moderate to severe
Cough Mid- Moderate Moderate to severe
Fatigue/Weakness Sometimes Usually, it can last up to 3 weeks
Sore Throat Common Common
Runny and stuffy nose Common On occasion
Chills No  Common
Sneezing Common  On occasion
Vomiting/diarrhea Rare Occasionally
Chest Discomfort  Mild  Common
Severity  Very low risk of complications if not immunocompromised  Serious health problems, such as pneumonia and bacterial infections, can occur.

As previously stated, it can be tricky to tell the difference between a cold and the flu, particularly in the early stages of infection. However, if specific symptoms are present, they can help differentiate between colds and the flu.

The flu is worse than the common cold in its severity. The common cold and the flu have incubation periods of around a week. Coughing and general weakness and weariness might linger for weeks after that.

A brief test of cold and flu viruses administered by medical professionals is the best method to tell the difference between a cold and the flu.

Diagnostic Methods 

Common colds and influenza are predominantly diagnosed based on the patient’s symptoms, but healthcare providers may also use a rapid test or other laboratory tests to confirm a flu diagnosis. Determining the cause of your symptoms can assist you and your practitioner develop a treatment plan. The following types of tests are generally used,

Self-Checkup Or Evaluation

Usually, a brief assessment of symptoms is sufficient to distinguish a cold or flu. If you are sure about what respiratory condition you have, you can look into things like,

  • Exactly when did symptoms start to show? Cold symptoms usually come on slowly, but flu symptoms often occur quickly.
  • Does your head or body hurt? The flu is much more likely than a cold to cause aches and pains in the joints, back, and head.
  • Do you feel feverish? Fever is more likely when you have the flu than when you have a cold. But you can get the flu without having a fever.
  • How weak and tired do you feel? Even though colds are unpleasant, most people can still go about their daily lives. Conversely, the flu can make you so tired or weak that getting out of bed is hard.

Physical Examination

Your doctor will do a physical exam to identify whether you have a cold or the flu.

Such as he/she will probably assess your temperature and pulse and ask questions about your symptoms (when they started, how bad they are, etc.) and vaccination history (whether or not you had the flu shot this year). To rule out problems like pneumonia, your doctor may also listen to your lungs and evaluate your breathing.

Yearly physical examinations are necessary even if you don’t have any medical condition. What things are evaluated in a physical exam? Click here to learn about it.

Lab Tests

Healthcare practitioners often diagnose colds and flu using a physical exam, but they may use other methods, such as laboratories and tests, to confirm the initial diagnosis. simple physical exam or self-check may typically detect cold, but many flu tests are available.

  • Rapid Influenza Diagnostic Tests (RIDTs): RIDTs are the most common tests to detect influenza viruses. A swab takes a sample from the inside of the nostril or a throat swab to detect proteins (antigens) on the virus’s surface and tests for the influenza virus. This tests take only 30  minutes to complete. This test has drawbacks as it doesn’t diagnose the specific strain causing infection and has lower accuracy than other lab tests, but it still does the job. 
  • Rapid Molecular Assays: A rapid molecular assay is another rapid test used to diagnose influenza. This sort of test is as fast as an RIDT (results in 15-30 minutes), but it provides more reliable findings. Virus nucleic acids, or RNA, may be detected using rapid molecular tools, and they are between 90% and 95% accurate.
  • Viral Culture: If more information about the specific strain, then growing and isolating the flu virus in a lab requires a more involved and time-consuming process called viral culture. It usually takes 3-10 days to give the results, which is why less commonly used.
  • At-Home Flu Test: testing for respiratory viruses at home has gotten much more accessible. In February 2023, the Food and Drug Administration (FDA) approved the first at-home flu test to detect COVID-19, influenza A, and Influenza B. It follows the same method of the throat and nasal swabs and gives the result within 30  minutes.

The accuracy of flu tests increases closer to the onset of symptoms; fewer than four days is optimal. It is best to consult a doctor sooner than later if you aren’t sure about your symptoms. If the test is negative, the patient likely has a cold unless their symptoms and signs become more severe.

In addition to tests to detect an influenza infection, flu testing may involve blood tests, chest X-rays, monitoring of oxygen levels, and other tests that can evaluate potential complications from an influenza infection.

Complications and Risk Factors

The following risk factors can increase the likelihood of getting a cold or flu,

Potential Complications of Cold and Flu

Cold and flu can cause complications, with some individuals recovering without severe consequences while others may experience more serious health issues. These complications, according to CDC, may include:

  • Pneumonia: Influenza can cause secondary bacterial lung infections, leading to pneumonia. This can be particularly hazardous for young children, elderly adults, pregnant women, and those with preexisting health conditions.
  • Ear Infections and Sinus: In children, influenza viruses might induce sinusitis and ear infections.(1)(2)
  • Worsening of Chronic Conditions: The influenza virus can aggravate chronic respiratory conditions such as asthma and chronic obstructive pulmonary disease (COPD), resulting in increased difficulty breathing and possible hospitalization. Even during a cold, asthmatics may experience worsening symptoms, resulting in respiratory difficulties.

You should consult a doctor if your symptoms are severe or if you are a member of a high-risk category, including children, the elderly, pregnant women, or those with preexisting health issues. The condition can be better managed and complications avoided if treatment begins early.

When to Seek Medical Help for a Cold

The majority of adults do not require medical attention for a common cold. Consult your doctor if you experience any of the following symptoms, however:

  • Symptoms that persist or deteriorate
  • Shortness of breath
  • A fever exceeding 101.3 degrees Fahrenheit that persists for more than three days.
  • A fever that returns after a relapse
  • Wheezing
  • Extreme pain, sinus or throat discomfort
  • Excruciating migraines that do not reduce
When to Seek Medical Help for a Flu

Adults with influenza typically address their symptoms at home and do not require medical attention. However, if you are at risk for flu complications, you should contact your doctor as soon as symptoms appear and seek immediate medical attention.

Emergency influenza symptoms include,

  • Ongoing dizziness
  • Breathlessness and difficulty breathing
  • An existing health condition that worsens
  • Severe Chest discomfort
  • Seizures
  • Severe muscle weakness or pains

The common cold and flu affect nearly everyone at some point. Still, with the proper knowledge and preventative measures, we may minimize the effects of the common cold and flu by being prepared and using effective preventative measures. Protect yourself and others from the flu and cold by prioritizing excellent hygiene, vaccination, and self-care. We have a detailed article about preventive measures and treatment.

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Dr Aimen

Being a Doctor by profession, Aimen is passionate about helping people get better health in their lives. Aimen enjoys her research on Prime With Time subjects and strives to create better awareness of the problems and changes related to women's health.

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