NEW DELHI: There is widespread panic across the world about Covid-19 caused by the novel coronavirus. But what does this insidious infection agent do to the human body? There are some answers after a review of nearly 56,000 Covid-19 cases from China, the country of origin of the perilous spread.
The review of the Chinese cases shows that the virus causes mild to moderate symptoms after infection in most cases, such as fever, dry cough and fatigue. But this is when the infection is limited to the upper respiratory tract — the nose and the throat. Once the infection involves the lower respiratory tract, complications set in.
The human lower respiratory tract consists of the windpipe (trachea), and the bronchi, bronchioles and alveoli that make up the lungs. These structures pull in air from the upper respiratory system, absorb the oxygen into the blood and release carbon dioxide in exchange.
A review of the Covid-19 cases that had turned severe and critical, comprising 14% and 6% of the total cases, respectively, showed infection caused by the virus damaging the lungs, therefore leading to shortness of breath in which the patient starts breathing faster, more than 30 times a minute, and a drop in the level of oxygen in the blood.
If the infection spreads to more than half of the lung, the oxygen transferring capacity of the organ gets affected. As a result, the oxygen level in the blood decreases. This lack of oxygen gradually affects the brain, heart and then the other organs.
“In severe cases when the lung is damaged, complications can be limited to symptoms such as shortness of breath and low oxygen saturation. But if this continues despite treatment, the patient may start getting restless and fall unconscious due to less oxygen in the brain. It can also affect the heart, kidneys and other body parts, leading to multi-organ failure,” explained Dr Arup Basu, senior pulmonology consultant, Sir Ganga Ram Hospital.
According to the WHO China Joint Commission report, 13.8% of the reviewed cases involved severe disease and 6.1% turned critical. “Individuals at highest risk of severe infection or death include people aged over 60 years and those with underlying conditions such as hypertension, diabetes, cardiovascular disease, chronic respiratory disease and cancer,” the report said.
Dr Basu explained that patients without other conditions usually recover from acute respiratory distress syndrome (ARDS) caused by an infected lung. “Those without a history of any underlying illness succumb to the condition only when there is a secondary bacterial infection,” he pointed out. “However, when patients already have serious or chronic conditions, it is possible the viral infection can cause septic shock or multi-organ dysfunction or failure.” This explains why the review reported most deaths occurred among the persons with co-morbidities.
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Dr Rommel Tickkoo, associate director, department of internal medicine, Max Saket, said treatment for Covid-19 is symptomatic because there is no specific drug or cure for it. “Management of a severe Covid-19 case involves ventilator support, fluid rehydration and fight against sepsis,” Tickkoo said. He noted that even in swine flu infection, the severe symptoms are similar to Covid-19, as is the management of the disease. However, unlike swine flu with a mortality rate of 0.03%, according to WHO data, mortality rate for Covid-19 is much higher at around 3.4%.
Histological examination of the post-mortem samples from a 50-year-old man from Wuhan showed how the lung was completely damaged by the infection. The medical report said there was “evident desquamation of pneumocytes and hyaline membrane formation”, which indicated acute respiratory distress syndrome.
A doctor said, “In a country like India where infrastructure for managing severe or critical symptoms is limited, it is all the more important to prevent Covid-19 from spreading.”