How to differentiate Covid, swine flu and seasonal flu?

Flu and Covid-19 are respiratory illnesses caused by different groups of viruses. Covid-19 appears to spread faster than other types of flu, especially at huge gatherings such as pep rallies, marriages, and festivals. Compared to the other types of respiratory illnesses, Covid-19 has the ability to cause severe illness and life-threatening post-Covid conditions.

It is possible for people to be infected with flu, as well as Covid-19, exhibiting symptoms of both diseases. There are similarities in the types of respiratory illnesses and it becomes difficult to identify the type of disease based purely on the presentation of their symptoms. Various tests need to be conducted to help identify the causative agent and further manage it as per said medical as well as government-mandated and approved guidelines.

That being said, loss of smell and taste is more commonly noted in Covid-19 and people with flu need not present with fever as one of the complaints. Diarrhoea is a common complaint in the young with flu-like symptoms as compared to the adult or the elderly population. The effects of the vaccination on the presenting symptoms are thought to make them milder, symptoms tend to last longer and the ability to spread the disease appears to increase.

The most commonly seen symptoms in the respiratory disease caused by viruses are fever, chills, the sensation of having fever without actually having high temperature, cough which can be both dry or productive, sense of breathlessness, tiredness, easy fatigue, giddiness, feeling faint, sore throat, running nose, nasal congestion or stuffy nose, muscle aches, generalized
body aches, headaches, nausea, vomiting, loss of appetite, diarrhoea, loss of smell, an altered sense of taste or loss of taste.

The more severe forms of complications in these include pneumonitis, pneumonia, respiratory distress or failure, life-threatening infections, heart attack, stroke, multi-organ dysfunction or failure, inflammation of the brain, muscles, blood clots in the blood vessels supplying the lungs, clots in the peripheral circulatory systems, secondary infection both bacterial and fungal, the altered blood supply to the large bones cause necrosis and subsequent fractures, spontaneous bleed from the lower gastrointestinal system have been documented. Grossly elevated blood sugar levels post recovery from Covid has been observed not just in diabetics but borderline and non-diabetics as well. Though the worst of the complications tend to occur at a higher frequency in Covid rather than the other respiratory illnesses.

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Importance of diagnostic tests

A panel of diagnostic tests is of utmost importance to correctly identify the kind of fever affecting the body. At the same time, encouraging flu shots is important, to rule out common colds and fevers. A sharp rise in dengue cases is being reported in many states. Not only are these cases increasing by almost 40 per cent as compared to last year, but we are also seeing cases of co-infection with Covid-19 and dengue fever attacking the body together has also come forward in private hospitals. The warning signs of severe dengue disease such as abdominal pains, persistent vomiting, and mucosal bleed help differentiate one from the others too. Undergoing diagnostic tests at the earliest to determine these co-infections for medical management can reduce mortality and morbidity to a large extent.

Which tests to go for?

Tests that help us in identifying viral respiratory illnesses are both blood and swab based. Rapid antigen kits are available to identify the type of virus. The more reliable being the swab tests for RT PCR test for H1N1, Influenza A, B, MERS, SARS COV2. Antigen and antibody qualitative and quantitative are also available which help us understand a slightly longer duration/late presenting cases, also aiding the medical management is the quantification of inflammatory markers to keep a tab on the progression or regression of disease. Radio diagnosis with the use of high-resolution imaging of the lungs can help us identify the possibility of the underlying cause and also how to respond to the medical management of the disease.