Acute Viral Fever

Fever is one of the oldest clinical symptoms of disease in the human as well as one of the most common reasons for medical consultations worldwide. Fever often occurs in response to infection, inflammation and trauma. Fever is a state of elevated core temperature, which is often part of the defensive responses of human to the invasion of live (micro-organisms) or inanimate matter recognized as foreign by the host. There is wide variation in normal body temperature in relation to several factors like age, physiological conditions, time of the day and site of temperature measurement. Body temperature exhibits a circadian rhythm i.e. morning temperature is usually lower than temperature in the afternoon (maximum around 4 PM). Fever in healthy adults may be defined as early morning oral temperature of >37.2 ◦C (>99 ◦F) or a temperature of >37.7 ◦C (>100 ◦F) at anytime during the day. Equivalent rectal temperature of ≥38 ◦C (100.4 ◦F) or axillary (armpit) temperatures of ≥ 37.5 ◦C (99.5 ◦F) are indicative of fever in both adults and children. People above 65 years of age are likely to have lower body temperature. In these people single oral temperature >100 0 F or repeated oral temperature of  >990F is indicative of fever. Rectal temperature is most close to core body temperature whereas temperature taken from armpit is least accurate.                                       

A virus is a small infectious organism that must invade a living cell to reproduce (replicate). The virus attaches to a cell (called the host cell), enters the cell, and releases its DNA or RNA inside the cell. The virus’s DNA or RNA is the genetic material containing the information needed to make copies of (replicate) the virus. The virus’s genetic material takes control of the cell and forces it to replicate the virus. The infected cell usually dies because the virus keeps it from performing its normal functions. When it dies, the cell releases new viruses, which go on to infect other cells.

Respiratory infections: 

Infections of the nose, throat, upper airways, and lungs. The most common respiratory infections are upper respiratory infections, which include sore throatsinusitis, and the common cold. Other viral respiratory infections include influenzapneumonia, and coronaviruses. Respiratory infections are common and one of the leading causes of morbidity and mortality particularly in young and elderly people. Influenza A & B, rhinoviruses, respiratory syncytial virus (RSV), adenoviruses and parainfluenza viruses are common respiratory virus in adults and children. Influenza is commonly reported respiratory infection and accounts for about 50% of respiratory infection. Fever is less common symptom in adults than in children. Fever is a less common presenting symptom in elderly people which may lead to diagnostic and treatment delays. The common symptoms of viral respiratory infections are nasal congestion, runny nose, cough, sore throat, sneezing, bodyache and fatigue. 

Co-infection with more than one virus is a strong predictor of high grade fever and so is smoking. Rates of hospitalization and ICU admission are higher in patients with dual respiratory infections. The treatment of viral respiratory infection is primarily aimed at symptoms relief and usually resolves within few days to within a week. In some parts of the world (especially Southeast Asia including India) antibiotics are extensively used to treat any form of mild respiratory illness. Although there may be some benefit of the use of antibiotics in preventing secondary bacterial infections, over-the-counter availability of antibiotics, self-medication, or medication administration by untrained pharmacy workers should be discouraged because of the selection and subsequent spread of resistance in community.     

Swine Flu:

Swine flu refers to influenza (flu) in pigs. Occasionally pigs transmit infection to human. Less often, someone infected with swine flu passes the infection to others. A particular virus known as H1N1 causes respiratory infection in human that is commonly called as swine flu. There are several other strains of such influenza viruses like H3N2 and others that cause such respiratory infections.

Influenza virus enters the body by inhalation of infected air droplets or transfer of viruses from contaminated surface to the eye, nose or mouth. The viruses infect the linings of nose, throat and lungs. Symptoms of swine flu are fever (but not always), chills, cough, sore throat, runny or stuffy nose, watery red eyes, body aches, headache, fatigue, diarrhea, nausea and vomiting. Flu symptoms develop after one to three days after the exposure.

It’s not necessary to see a doctor if the person is generally healthy and develop flu symptoms, such as fever, cough and body aches. However, if there is flu symptoms in pregnant female, or in a person with chronic conditions such as asthma, emphysema, diabetes, heart disease, liver disease, kidney disease, blood disorder or morbid obesity (BMI> 40), there is a higher risk of complications. The complications of influenza are worsening of chronic conditions, pneumonia, neurological symptoms like confusion and seizures and respiratory failure.

Doctor may advise to go for diagnostic testing with the swab samples taken from nose or back of throat for detection of the specific substances. These tests may not be accurate to rule out the disease and doctor depends on symptoms even if the test is negative. 

There are specific medicines used for the treatment of swine flu. However, most people with swine flu require symptomatic relief only. Drinking plenty of fluids, sleeping, rest and pain relievers (paracetamol & ibuprofen) are usually adequate for symptoms relief. The doctor may prescribe specific medicines for swine flu if there is a high risk of complication.    

There are specific vaccines available for swine flu that are effective in preventing the disease. These vaccine are effective for most of the strains of viruses like H1N1 and H3N2. Other measures to avoid swine flu are staying away from crowd in high risk area, confine if feeling sick, wash hands frequently with soap and water or alcohol based sanitizer, contain cough & sneezes.

Dengue Fever:

Dengue fever is a mosquito born disease that affects millions of people around the world. Dengue fever is caused by any one of four types of dengue viruses spread by mosquitoes that thrive in and near human lodgings. When a mosquito bites a person infected with a dengue virus, the virus enters the mosquito. When the infected mosquito then bites another person, the virus enters that person’s bloodstream.

Many people, especially children and teens, may not experience any symptom during a mild case of dengue fever. Mild dengue fever causes a high fever, rash, and muscle and joint pain. Dengue fever cause high grade fever -1040F along with headache, muscle, bone & joint pain, nausea, vomiting and rash. Most people recover within a week or so. In some cases, symptoms worsen and can become life-threatening. The number of clot-forming cells (platelets) in the bloodstream drops significantly. A severe form of dengue fever, also called dengue hemorrhagic fever, can cause severe bleeding, a sudden drop in blood pressure (shock) and death. Papaya leaf extract or its formulations like tablets, capsules and syrup are available which can be given to increase the platelets. This can be started immediately or any time in between after the diagnosis of dengue fever is confirmed.

After the person recovers from dengue fever, he develops immunity to the type of virus that infected him — but not to the other three dengue fever virus types. The risk of developing severe dengue fever, also known as dengue hemorrhagic fever, actually increases if person is infected a second, third or fourth time.

There is no specific drug for the treatment of dengue fever. The patients are managed by giving supportive treatment to relieve symptoms and prevent further complications. No vaccine is available in India for dengue fever. Controlling the mosquito population and human exposure is the most critical part of disease prevention. Person should use mosquito repellants &wear protective clothing in high risk areas.


Chikungunya virus is primarily transmitted by Aedes mosquitoes. Though reports of an illness consistent with chikungunya date back over 200 years, it only gained worldwide attention during a massive pandemic that began in East Africa in 2004. The incubation period of chikungunya ranges from 1 to 12 days. Chikungunya typically presents as acute onset high grade fever, debilitating joint pain and rash. The joint involvement is bilateral and commonly involves knees, ankle, wrist and smaller joints of hands and feet. Headache and gastrointestinal complaints, such as anorexia, nausea, vomiting, and abdominal pain, are also commonly reported in chikungunya cases. Patients above 65 years may present with more severe complications including neurological complains.   

The diagnosis of chikungunya can not be confirmed solely based on clinical symptoms. The disease is diagnosed based on molecular and serological tastings and antigen detection. Though the number of cases declined significant from 2014 to 2017, sporadic outbreaks continue to occur in Asia and Africa. During an outbreak, chikungunya virus is maintained in a human-mosquito-human cycle of transmission by Aedes mosquitoes, in a pattern similar to that for dengue virus. The studies have also shown chikungunya dengue coinfection in good number of patients.    

There is no specific antiviral drug for the treatment of chikungunya and management remains symptomatic and supportive. The symptoms of chikungunya usually resolve within 1 week.  Approximately 50% of patients have chronic arthralgia and/or arthritis at 3 to 6 months, and over 25% of patients may still have symptoms at 12 months, which negatively impacts quality of life during recovery. Mosquito control is primary mode of chikungunya prevention.


Coronaviruses are a family of viruses that can cause illnesses such as the common cold and severe acute respiratory syndrome (SARS). In 2019, a new coronavirus was identified as the cause of a disease outbreak that originated in China. The virus is known as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The disease is called coronavirus disease 2019 (COVID-19). In March 2020, the World Health Organization (WHO) declared the COVID-19 outbreak a pandemic.

Signs and symptoms of coronavirus disease 2019 (COVID-19) may appear two to 14 days after exposure. Common signs and symptoms can include fever, cough, and tiredness. Early symptoms of COVID-19 may include a loss of taste or smell. Other symptoms can include shortness of breath or difficulty breathing, muscle pains, chills, sore throat, runny nose, headache and chest pain. Less common symptoms have been reported as rash, vomiting, diarrhea and abdominal pain. The severity of COVID-19 symptoms can range from very mild to severe. Some people may have only a few symptoms, and some people may have no symptoms at all. Some people may experience worsened symptoms, such as shortness of breath and pneumonia, about a week after symptoms start. Patients with advanced age and concomitant diseases have high risk of severe symptoms and complications due to Covid-19. Some of the risk factors for severe illness are age above 65 years, high blood pressure and other cardiac illness, diabetes, obesity, cancer, asthma and other lung disease and smoking.

The virus appears to spread easily among people, and more continues to be discovered over time about how it spreads. Data has shown that it spreads from person to person among those in close contact (within about 6 feet, or 2 meters). The virus spreads by respiratory droplets released when someone with the virus coughs, sneezes or talks. These droplets can be inhaled or land in the mouth or nose of a person nearby. It can also spread if a person touches a surface with the virus on it and then touches his or her mouth, nose or eyes; although this isn’t considered to be a main way it spreads.

Although most people with COVID-19 have mild to moderate symptoms, the disease can cause severe medical complications and lead to death in some people. Older adults or people with existing chronic medical conditions are at greater risk of becoming seriously ill with COVID-19. Complications due to Covid-19 can include pneumonia and trouble breathing, organ failure in several organs, heart problems, acute respiratory distress syndrome, blood clots, acute kidney injury and other viral or bacterial infections.

Although there is no vaccine available to prevent COVID-19, WHO and CDC recommend following precautions for avoiding COVID-19:

  • Avoid large events and mass gatherings.
  • Avoid close contact (within about 6 feet, or 2 meters) with anyone who is sick or has symptoms.
  • Stay home as much as possible and keep distance between yourself and others (within about 6 feet, or 2 meters), especially if you have a higher risk of serious illness. Keep in mind some people may have COVID-19 and spread it to others, even if they don’t have symptoms or don’t know they have COVID-19.
  • Wash your hands often with soap and water for at least 20 seconds, or use an alcohol-based hand sanitizer that contains at least 60% alcohol.
  • Cover your face with a cloth face mask in public spaces, such as the grocery store, where it’s difficult to avoid close contact with others, especially if you’re in an area with ongoing community spread. Only use nonmedical cloth masks — surgical masks and N95 respirators should be reserved for health care providers.
  • Cover your mouth and nose with your elbow or a tissue when you cough or sneeze. Throw away the used tissue. Wash your hands right away.
  • Avoid touching your eyes, nose and mouth.
  • Avoid sharing dishes, glasses, towels, bedding and other household items if you’re sick.
  • Clean and disinfect high-touch surfaces, such as doorknobs, light switches, electronics and counters, daily.
  • Stay home from work, school and public areas if you’re sick, unless you’re going to get medical care. Avoid public transportation, taxis and ride-sharing if you’re sick.

The diagnosis of Covid-19 is made by molecular testing or rapid antigen testing. Rapid antigen testing is useful as a mass screening tool whereas molecular testing by RT-PCR is done for confirmation.   There are several oral and injectable drugs are used for the treatment of Covid-19 but no documented cure is available. Antibiotics are ineffective against viral infections. Many clinical studies are underway to find a cure of this disease. The available treatments for covid-19 are primarily supportive and directed towards controlling the inflammatory response and acute complications. Several vaccines for covid-19 are under various phases of clinical trials and promise a great hope for prevention of this disease.