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Viral fever

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Viral fever, an illness associated with an increase in average body temperature, is caused by a virus. Because of environmental factors, it can be categorised as either a seasonal fever or fever. 

Viral fever is the most common symptom caused by an infection and helps recognise the condition of the disease. Fever is caused by the invasion of disease-causing viruses such as chikungunya virus, hantavirus, Salmonellaserovars, rhinovirus, adenovirus and influenza virus.The incubation period for these viruses ranges between 1 and 4 days before the onset of an increase in body temperature. 

The route of viral transmission can be person to person via the inhalation of respiratory droplets, which occurs when an infected person coughs or sneezes. Moreover, the transmission may occur because of mosquitos.

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Viral fever is categorised based on different viral infections caused by different viruses.

1. Respiratory viral infection

  • Note that >100 viruses, such as rhinoviruses, influenza A and B, coronaviruses, and adenoviruses, cause respiratory tract infections.

  • Fever in respiratory tract infections most commonly occurs in infants and young children and often in adults.

  • Viral fever, which occurs for five days or longer in children with this infection, may last for 3–5 days. The most prolonged fever of seven days is caused because of adenovirus, and the shortest duration of fever is caused by parainfluenza virus.

  • Influenza A virus and adenovirus infection occur more frequently in children having a high-grade fever while fever because of rhinovirus is usually absent or mild.

  • COVID19 is a type of respiratory illness caused by a newly discovered coronavirus. It is transmitted from person to person via respiratory droplets when an infected person either coughs, sneezes, breathes, or talks.

2. Gastrointestinal viral infection

  • Rotavirus and calicivirus are typical virus-causing pathogens causing gastrointestinal infections.

  • The highest frequency of rotavirus infection occurs in children less than five years of age with an incubation period of 1–3 days. Most children with a rotavirus infection have a fever of 39–40°C along with diarrhoea and dehydration.

  • Usually, a low-grade fever lasts for 1–3 days and is associated with adenovirus enteritis with a range of body temperature between 36.2 and 40.8° C.

  • Fever occurs because of calicivirus gastroenteritis occurs along with the sudden onset of abdominal cramps and nausea and lasts for 48 h.

3. Yellow Fever 

  • Yellow fever is caused by the yellow fever virus, which is transmitted by infected mosquitos. When the person is infected, the yellow fever virus incubates in the body for 3–6 days, and the fever lasts for 6–8 days.

  • Jaundice is a common symptom that affects patients. Other common symptoms are fever, muscle pain, headache, appetite loss and vomiting.

  • Jaundice is most common in tropical areas of Africa and South America.

4. Dengue fever

  • Mosquitoes transmit dengue fevers. Aedes mosquitoes are globally the leading cause of insect-borne viral disease.

  • It is called breakbone fever because of muscle spasms and joint pain.

  • Usually, the fever lasts for seven days, in addition to the usual occurrence of symptoms.

5. Viral hepatitis

  • Viral hepatitis is a viral infection causing inflammation and liver damage. The inflammation causes swelling to tissues, which in turn damages the organs.

  • There are different types of viruses that cause hepatitis, including hepatitis A, B, C, D and E.

  • Hepatitis A and B spread via contact with food or water that has been contaminated by an infected person’s stool. These are acute infections that do not lead to chronic infection and have fewer complications.

  • Hepatitis B, C and D spread via contact with an infected person’s blood or other body fluids. These can cause chronic, long-lasting infections that lead to complications such as cirrhosis, liver failure and liver cancer.

  • Hepatitis A, B and D can be prevented by vaccination. There are no vaccines available for the hepatitis C virus.


Viral fever appears with the onset of an increase in body temperature as soon as the virus enters the host cell. The fever appears in three stages:

  • Incubation: The incubation period for the virus range between 1 and 4 days before the onset of an increase in body temperature. A person may be asymptomatic.

  • The onset of Illness: A person is considered infectious from the day of onset of fever, which may persist for particular time duration and other symptoms such as cold, cough, or body ache

  • Recovery: During this phase, there is a decrease in the increase in body temperature, and there is normal body functioning.


Viral fever is a symptom caused by any infection because of which the body temperature reaches 100.4°F or higher. The signs of viral fever vary as per the infection:

  • Flushed face

  • Hot and dry skin

  • Appetite loss

  • Nausea and vomiting

  • Body ache

  • Restlessness

  • Weakness

  • Chills

  • Cough

  • Cold

  • Burning sensation in eyes

A high fever that rapidly rises may cause severe conditions such as seizures in children. One must take essential care of babies, young children, and disabled people.

Coronavirus-related symptoms range from mild to moderate depending on the infection’s severity:

Most common symptoms include:

  • Fever and chills

  • Cough

  • Tiredness

  • Muscle and body ache

  • Sore throat

  • Loss of taste or smell

Serious symptoms include:

  • Difficulty breathing or shortness of breath

  • Chest pain

  • Difficulty in moving

  • Loss of speech

Causes And Risk Factors


Viral pathogens may cause a high- or low-grade viral fever because of different viral pathogens that invade the body. The different infection-causing viral pathogens are the chikungunya virus, hantavirus, rotavirus, calicivirus, and coronavirus.

Common illnesses caused because of these pathogens that contribute to fever are listed below:

  • Cold or flu

  • Bronchitis

  • Gastroenteritis

  • Respiratory tract infections

Certain other causes that may bring change in a person's average body temperature are listed below:

  • Stress

  • Emotional changes

  • Improper eating habits

  • Certain medications

  • Heavy clothing

Risk Factors

The occurrence of a viral fever varies between populations, ages and geographical locations. Children are at a higher risk of developing a fever compared to adults because of an inadequate immune response.

Other factors contribute to a high risk for viral fevers.

  • Insects such as mosquitos, ticks and rodents are capable of infecting the host.

  • Close contact with infected people.

  • Travelling to developing countries and having low immunity


Viral fever can quickly spread; therefore, it is necessary to take precautions to avoid the risk of infection.

  • Maintain good hygiene.

  • Avoid contact with infected people.

  • Maintain healthy eating habits to increase immunity

  • Protective clothing can prevent infection because of insects and rodents

  • Avoid touching eyes, nose and mouth

  • Consumption of multivitamin or vitamin D supplements

Annual vaccination for conditions such as yellow fever and dengue fever helps to fight against these infections.

The best advice to prevent coronavirus include:

  • Maintain a safe distance of 6 feet from others whenever possible

  • Wear a mask that covers your mouth and nose in public

  • Wash your hands frequently with soap or sanitiser to keep it germ-free

  • Self-isolation is necessary if you show any of the possible COVID-19 symptoms

  • Clean and disinfect frequently touched surfaces


An appropriate diagnosis helps identify the severity of viral fever and form appropriate treatment measures. The diagnostic tests include-

  • Thermometer: A thermometer can easily detect the initial onset of a fever with a thermometer. The temperature rise can be detected by a digital thermometer or a glass thermometer that contains Hg. People can use the digital thermometer to record temperature orally, rectally or by placing it under the armpit. In adults, the temperature is taken by placing the thermometer under the armpit or in the mouth.

  • Blood Test: Blood tests help rule out any other condition and detect the presence of the causative agent of the infection. In a viral fever, the blood sample helps to detect antibodies and viral antigens within seven days of the occurrence of infection.

  • RT-PCR test: This test helps in the rapid detection of the specificity and sensitivity of the disease in the initial days of the illness. The

  • RT-PCR test can detect a viral nucleic acid that helps identify the viral load in the body. Rapid tests have allowed for prompt diagnosis and initiation of antiviral therapy and a decrease in the inappropriate use of antibiotics.

  • One must do a sputum evaluation for respiratory tract symptoms such as cold, cough or sore throat.

  • The diagnosis of the coronavirus includes laboratory tests that require the collection of samples of saliva or swabs of your nose to send for testing.


Viral fever with a temperature of <101°F is categorised as a low-grade or mild fever and requires no medical treatment. General measures taken to manage the temperature are listed below:

  • Administration of fluids to replenish losses

  • Stay at home and get plenty of rest

  • Eat a light diet

  • Discontinuation of medications that may be responsible for fever.

For high-grade viral fever, there are many ways in which the body can bring it under control. The common ways include 

  • Hospitalisation: If the fever is caused by a severe infection, the person must be admitted to the hospital. Patients that possess low immunity or have any other existing condition may require hospital admission. The administration of intravenous fluids and management of anxiety and electrolyte imbalance is possible during hospitalisation. People must be closely monitored for complications such as multi-organ dysfunctions and haemorrhagic events. 

  • Antipyretic therapy: The administration of medications such as paracetamol or ibuprofen is initially given to provide symptomatic relief. Prescribers should give it in response to fever to monitor the temperature. 

  • Evaporative cooling: It is a technique that is used in patients with a temperature of >105°F. The patient is sprayed with cool water all over the body and kept under a fan; for patients with a fever of 98°F, it may help in bringing down the body temperature. 

  • Antiviral therapy: Empirical antiviral treatment with ribavirin is used for viral haemorrhagic fever. This drug inhibits the replication of the virus inside the host, thus leading to a decline in temperature. 

  • Oseltamivir and zanamivir are used to treat influenza in patients and can be used in children above two years of age or older. Amantadine and rimantidine have been approved to treat influenza, but flu viruses are widely resistant. 


  • People must maintain good personal hygiene. Regular showers with hot water daily may help to kill disease-causing pathogens. 

  • A person that is prone to developing recurrent episodes of fever must keep a check on immunity. A healthy diet including fruits and vegetables helps to keep up body fluid and electrolyte balance. 

  • An adequate amount of sleep is necessary to maintain the activity level throughout the day and regulate the normal body functioning. 

  • The management of stress and anxiety is essential because it contributes to the regulation of body temperature. 

Prognosis And Complications


The outlook for people with a viral fever varies as per the specific disease. Patients with symptoms associated with a viral fever such as headache and body pain should closely monitor cough and sore throat. If the symptoms do not resolve in a week, one must take appropriate measures to identify the infection. 

People over 65 or those with chronic illnesses have an inadequate immune response for fighting infections, and a viral fever may lead to complications, hospitalisation or death. 


High-grade fever with a temperature of >101°F lasting for more than two days may account for a possible infection or development of serious complications:

  • A viral fever accompanied by a stiff neck, rash, confusion or irritability. 

  • An excessive amount of dehydration can cause loss of body fluids because of an increase in viral load. 

  • A high fever in children may develop seizures. 

A fever in an adult that goes >105°F and does not come down with treatment may cause life-threatening complications including 

  • Oedema because of fluid accumulation. 

  • Failure of organs, including lungs, kidneys and brain

  • Internal bleeding


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