Cold & flu – The most common viral infections

The common cold earns its name from being the most common infectious disease [1]. Despite this, it is often confused with the seasonal flu [2]. While colds are the leading cause of missed school days for children and work absences for adults, the flu is responsible for annual epidemics. [1-3].

What is the difference between cold and flu?

The cold and the flu, also called influenza, have a lot in common. Both are contagious respiratory illnesses caused by viruses – though different ones – and both produce similar symptoms [3]. These similarities make it very difficult to tell them apart, especially in the early stages of illness [2]. Generally, flu symptoms are more severe than those of the common cold, often more intense and with a sudden onset [2]. On the other hand, colds are usually milder and, in most cases, do not lead to serious health problems. The flu, if not treated properly, can result in complications such as pneumonia, bacterial infections, or even hospitalizations [2,4]

Common cold

The common cold is a self-limited, contagious condition caused by several types of viruses, including rhinoviruses, parainfluenza, and seasonal coronaviruses [3]. These seasonal coronaviruses, however, should not be confused with SARS-COV-2, the virus that causes COVID-19 [5]. The common cold is the leading cause of acute morbidity and missed days from school or work. Adults have an average of 2-4 colds per year, while young children have 6-8 [3]. Although people most often catch colds in the winter and spring, they can occur at any time of year. The cold spreads especially quickly during winter [3], primarily through airborne droplets released when a sick person coughs or sneezes, which others then inhale. The virus can also spread through surface contamination or direct contact with a sick person [6]. 

Flu (influenza)

The flu is caused by influenza viruses only [2]. The two main types of influenza viruses are Types A and B. Both types are responsible for seasonal flu epidemics each year [2]. Sometimes the flu causes mild illness. But it can also have a serious progression and even lead to death. The flu is especially dangerous for vulnerable individuals over 65, newborns, and people with certain chronic conditions or immune deficiencies [4,10]. Like cold viruses, flu viruses also enter the body through the mucous membranes of the nose, eyes, or mouth [7]. They spread quickly from person to person through tiny droplets from coughing, sneezing, or even just talking. Although less common, it is still possible to contract the virus by touching contaminated surfaces or objects [8].

Common symptoms

Even though it’s not always easy to tell whether it is the common cold or the flu, understanding the differences in symptoms can be helpful. In general, the common cold is a milder respiratory illness compared to the flu [2].

Cold symptoms

The first cold symptoms usually start 2 to 3 days after the virus enters the body, and symptoms last from several days to several weeks. The course of the illness is usually less intense without fever, and milder symptoms such as runny nose can last several weeks. [6]. 

Here are the most common cold symptoms [6]:

  • Runny or stuffy nose
  • Scratchy throat
  • Sneezing
  • Watering eyes
  • Low-grade fever
  • Sore throat
  • Mild cough
  • Muscle or body aches
  • Headaches
  • Mild fatigue
  • Chills
  • Watery discharge from nose that thickens and turns yellow or green

Flu symptoms

Most flu symptoms improve over two to five days. Many symptoms such as sore throat, fever, and cough tend to develop rapidly. General fatigue can even last for weeks [9] The flu's progression is more severe than a cold, and flu-related complications (such as pneumonia) can occur, particularly in the young, elderly, or people with lung or heart problems [4,10]. 

Here are the most common flu symptoms [4]:

  • Fever* or feeling feverish
  • Chills
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headaches
  • Fatigue (tiredness)
  • Vomiting and diarrhea (more common among children)

* not everybody with flu will have fever

The difference between a cold and the flu

It’s not easy to differentiate between the two. Here’s an overview of symptoms that can indicate the cause of the illness.

Symptoms
Cold
Flu

Symptom onset

gradual

sudden
Symptom severity
mild to moderate
moderate to severe
Fever
rare
Common; lasts 3-4 days
Headache
rare
common
Sore throat
common
occasionally
Aches and pain
slightCommon; often severe
Chills
uncommoncommon

Cough, chest discomfort

mild to moderate
common, can be severe
Sneezing
common
occasionally
Fatigue
rarecommon

How to prevent common colds and the flu?

There are certain everyday preventive actions that can minimize the chance of contracting viruses as well as reduce the spread of viral infections.

Get vaccinated – The first and most crucial step in protecting against flu viruses is getting vaccinated. A yearly flu vaccine is available that can help reduce the burden of flu illnesses, hospitalizations, and deaths in the health care system [10].

Wash hands

The most straightforward and fastest task is to wash hands thoroughly and often with soap and water. An alcohol-based hand rub is a good alternative if soap and water are unavailable [11].

Disinfect stuff

Doorknobs, light switches, electronics, as well as kitchen and bathroom countertops are considered high-touch surfaces and should be cleaned and disinfected regularly [11]. 

Avoid people with viral infections

Close contact with people who have viral infections increases the chances of getting it. Avoid such situations but also stay out of large crowds, especially during flu season [11].

Maintain a healthy lifestyle

A healthy diet, exercise, and sufficient sleep, in general, promote overall health [11].

Strengthen the immune system

Another very effective way to prevent viral diseases is maintaining an overall strong immune system. There are healthy strategies that have proven health benefits. These include a diet high in fruits and vegetables, exercise regularly, maintain a healthy weight, get adequate sleep and minimize stress.  Overall, good health has positive effects on the immune system itself [12]. 
Consuming adequate amounts of several vitamins and minerals—including vitamin A, vitamin C, vitamin D, vitamin E, selenium, and zinc—is important for proper immune function.  [13]. Natural medication has proven itself as a safe and effective alternative. Many natural ingredients can help stimulate the immune system, supporting both the prevention and treatment of viral infections [14].

How to treat common colds and the flu?

There is no cure for most viral respiratory illnesses. Therefore, treatment focuses primarily on relieving symptoms; however, there are some proven methods to help manage them [15]:

Drink plenty

Water, tea, broth, and warm liquids, in general, can be soothing for a sore throat, prevent dehydration and ease congestion. At the same time, it is good to restrain from salty foods, alcohol, coffee, and sugary drinks.

Gargle salt water

Gargling a glass of warm water with about one teaspoon of salt can help reduce the pain of a sore throat.

Humidify the air

Viruses spread better in dry air, and at the same time, dry air can worsen a sore throat. A humidifier will evaporate the water, especially in the bedroom, making it more soothing. Another option is to place a shallow water bowl out near a heat source.

Rest

During an illness, the body works non-stop, and the immune system needs time to recharge. Rest and sleep are essential in overcoming a cold or the flu, which also means restraining from exercise.

Avoid smoking

Smoking and exposure to smoke can irritate the nose, throat, and lungs and therefore prolong the illness.

Pharmacological approach

Most mild viral respiratory illnesses are managed symptomatically with synthetic medications. These include nasal decongestants, antipyretics/analgesics like paracetamol, and non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin, or ibuprofen. Even though most conventional treatment options are readily available as over-the-counter (OTC) medications, patients should be aware of potential risks or harmful effects. Especially NSAIDs can lead to harmful cardiovascular side effects.  In addition, a Cochrane review concluded that there is no clear evidence of the effectiveness of NSAIDs in treating respiratory symptoms of the common cold other than relieving associated discomfort and that the balance of benefits and harms needs to be considered when using NSAIDs for colds .
Decongestants can harm the nasal mucosa, and long-term use may lead to tolerance, addiction, and re-bound effects [15-19]. 

Natural medicine approach

Since pharmaceutical antiviral substances are often associated with side effects, a growing number of people rely on natural medications that have a good safety profile and are well tolerated in a broad range of patient types. Plant-based medications with natural ingredients from the pharmacy can help with viral infections and common colds by supporting the defense system of the body, without the need for a prescription. They can help your immune system respond more effectively, leading to milder symptoms and a quicker recovery [20,21].

Heel natural medicines

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  15. Johns Hopkins Medicine. The do’s and don’ts of easing cold symptoms. [date unknown]. Available from: https://www.hopkinsmedicine.org/health/wellness-and-prevention/the-dos-and-donts-of-easing-cold-symptoms. Accessed June 5, 2025.
  16. World Health Organization. The use of non-steroidal anti-inflammatory drugs (NSAIDs) in patients with COVID-19. 2020 Apr 19. Available from: https://www.who.int/news-room/commentaries/detail/the-use-of-non-steroidal-anti-inflammatory-drugs-(nsaids)-in-patients-with-covid-19. Accessed June 5, 2025.
  17. U.S. Food and Drug Administration. FDA strengthens warning that non-aspirin nonsteroidal anti-inflammatory drugs (NSAIDs) can cause heart attacks or strokes. 2015 Jul 9. Available from: https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-fda-strengthens-warning-non-aspirin-nonsteroidal-anti-inflammatory. Accessed June 5, 2025.
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