Over 1,000 unique viruses can affect us. Some, like the common cold and flu, affect the respiratory tract, while others cause inflammation of the intestines, liver, or other organs. Some infections are self-limiting — meaning they resolve with no or minimal treatment in about a week — while others have long-term, serious consequences.

Viral infections are contagious, spreading from person to person through surface contamination, food, water, or sex. Some general symptoms suggest a viral infection, but it's always best to see a doctor for a diagnosis.


Virtually all infections can cause a lack of energy. The symptom stems from increased levels of inflammatory cytokines — immune cells. Sleep is often disturbed due to the viral illness, causing more fatigue the next day. Brain fog and irritability typically follow.

Some viruses, like Epstein Barr, can cause fatigue for several months or even years. Research has linked the Epstein Barr virus, which is responsible for mononucleosis, with chronic fatigue and fibromyalgia.


Scratchy Throat

One of the ways to differentiate between a common cold and flu is that the former causes a scratchy, sore throat that lasts a couple of days. Epstein Barr infections and respiratory syncytial virus (RSV) can also cause a scratchy throat. This symptom may be associated with cough, runny nose, and sneezing.


Runny, Stuffy Nose

Nasal congestion is a common symptom of viral infections, as the nose is the main entry point for airborne viruses. Coronaviruses and other viruses that cause the common cold, as well as RSV, are often the underlying cause, especially during the colder seasons.

Other diseases, like allergies or bacterial sinusitis, can cause stuffy nose and nasal discharge that may be clear, white, or yellowish.



Many viral infections cause headaches, either through direct or indirect mechanisms. In many cases, the headache is related to fever, dehydration, and the production of interferon and other molecules used by the immune system to fight the infection.

Infections with rhinoviruses often cause nasal and sinus congestion, which can also lead to a headache. In some cases, a severe headache indicates a viral infection of the brain and the brain's membranes, such as encephalitis and meningitis.


Nausea and Vomiting

Many viral infections, especially ones that affect the intestines, cause nausea and vomiting. Other digestive complaints like lack of appetite, abdominal discomfort and cramps, and diarrhea can also occur. In case of viral gastroenteritis, symptoms last for a day or two, but they may persist for up to 10 days.



Fever enhances the body’s immune response to an infection, but it is absent or mild in many viral infections.

Some cases of influenza and adenoviruses, however, can cause fevers of 40 degrees C or even higher that can last 3 to 5 days. Bacterial infections also tend to cause a high fever. Fever and chills often occur together: chills are the body’s response to raise the core temperature through muscle contraction and relaxation.



Flu and other viral infections affecting the respiratory tract can cause chest discomfort and cough. A congested nose and sinuses can further aggravate these symptoms. Chest pain aggravated by cough, rapid breathing, breathing, fatigue, fever, and chills suggests inflammation of the lungs or pneumonia, which could be the result of influenza or RSV viruses, various bacteria, or fungi.


Body Aches and Pains

The flu and many other viral infections are associated with body aches and pains, weakness, and fatigue. Contrary to popular belief, the body’s aches are not due to the virus but the body’s immune response to the virus. This protective response leads to inflammation in the muscles or myositis.

When pain and inflammation affect the joints, fever is often present as well. Non-steroid anti-inflammatory drugs can help relieve these muscle and joint aches.



Malaise is more than fatigue. It is a persistent feeling of extreme exhaustion, lethargy, and illness that is not relieved by rest.

Chronic viral diseases like HIV infections and viral hepatitis, as well as non-infectious conditions such as heart and autoimmune diseases and cancer, are common causes of malaise. Some medications can cause fatigue or malaise, too.


Lack of Appetite

It is normal to lose your appetite when fighting an infection. Fatigue, interrupted sleep, nausea, and vomiting can all make people less hungry than usual. In case of acute infections, the appetite returns to normal when the other symptoms improve and the body recovers.

It is important to stay well hydrated during a viral infection. Fever, vomiting, and diarrhea increase dehydration, and dehydration aggravates the symptoms. Chronic infections like HIV and hepatitis can lead to significant weight loss due to appetite loss and other symptoms.


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