Symptomatic, asymptomatic COVID-19 cases and our immune system
These viruses (corona) were first discovered in the 1930s when an acute respiratory infection of domesticated chickens was reported
Azad Amin
Today nearly whole world is suffering from the one of the worst pandemic and due to this more than one-third of the world is under lockdown as governments urge social distancing to stymie the virus’ spread. There are still no drugs that can kill this virus or vaccines that can protect us against it. The patients of Covid-19 can be either symptomatic or asymptomatic.
Symptomatic
According to WHO Symptomatic Covid-19 patients show most common symptoms of like fever, tiredness, and dry cough. Some patients may have aches and pains, nasal congestion, runny nose, sore throat or diarrhea. These symptoms are usually mild and begin gradually. Some people become infected but don’t develop any symptoms and don’t feel unwell. Most people (about 80%) recover from the disease without the need of any special treatment. Around 1 out of every 6 people who gets COVID-19 becomes seriously ill and develops difficulty breathing.
Older people, and those with underlying medical problems like high blood pressure, heart problems or diabetes, are more likely to develop serious illness. People with fever, cough and difficulty breathing should seek medical attention.
These viruses (corona) were first discovered in the 1930s when an acute respiratory infection of domesticated chickens was reported to be caused by infectious bronchitis virus (IBV). But Human coronaviruses were discovered in the 1960’s. They vary significantly in risk factor. Some can kill more than 30% of those infected (such as MERS-CoV), and some are relatively harmless, such as the common cold.
In December 2019, a pneumonia outbreak was reported in Wuhan, China, this outbreak was traced to a novel strain of coronavirus, which was given the interim name 2019-nCoV by the World Health Organization (WHO), later renamed SARS-CoV-2 by the International Committee on Taxonomy of Viruses. Some researchers have suggested the Huanan Seafood Wholesale Market may not be the original source of viral transmission to humans.
Asymptomatic
One will be considered asymptomatic if he:
• Have recovered from an illness or condition and no longer have symptoms.
• Have an illness or condition (such as glaucoma) but do not have symptoms of it.
A recent study, published in the British Medical Journal, suggested that 78% of people with COVID-19 have no symptoms. Meanwhile, a WHO report found that “80% of infections are mild or asymptomatic, 15% are severe infections and 5% are critical infections”. The first confirmation that the novel coronavirus could be transmitted by asymptomatic people came in February, when a case study described a 20-year-old woman from Wuhan, China, who passed the coronavirus to five family members but never got physically sick herself.One potential group of asymptomatic carriers could be children. So far children are among those least affected by the coronavirus – but some could be getting very mild infections thus spreading the virus.
Ultimately, widespread antibody testing, which is still not imminent, will be able to tell us how many people have already had COVID-19. This will give a better approximation of the total number of infections. This will be important in making decisions on lifting social distancing measures. For example, if antibody testing suggests that a large proportion of the population has had COVID-19 already, there is a smaller chance of asymptomatic and undiagnosed cases spreading the infection once restrictions are lifted. But if only a very small proportion of the population has had the infection, then lifting of social distancing measures may have to be delayed until vaccination strategies are ready to be implemented
Natural Defence (Immune System)
The coronavirus pandemic has turned the world’s attention to the immune system, our body’s defence force against disease-causing bacteria, viruses and other organisms that we touch, ingest and inhale every day. The body’s natural barriers against disease-causing intruders – for example, our skin, the mucous and hairs in our nose, and the acid in our stomachs – are part of our innate immune systems.
Adaptive immunity develops over a lifetime of contact with pathogens and vaccines, preparations which help our immune systems to distinguish friend from foe. There has been no concrete study on human immunity to the novel coronavirus so far. But studies of other coronaviruses have led researchers to believe that people who have recovered from SARS-CoV-2 infection will be protected from re-infection for a period of time.
Sometimes the host immune system response is so strong that its effect can be counterproductive. For example, numerous immune cells can enter our lungs and cause the membrane through which oxygen normally passes from the air into the blood to thicken. The exchange of gases is restricted, and in the worst case, ventilation may be necessary. The balance between protective and overly aggressive immune processes in dealing with the coronavirus is currently a big mystery. This must now be investigated.
Virus infected cells of our body produce and release small proteins called interferons, which play a role in immune protection against viruses. Interferons prevent replication of viruses, by directly interfering with their ability to replicate within an infected cell. They also act as signalling molecules that allow infected cells to warn nearby cells of a viral presence – this signal makes neighbouring cells increase the numbers of MHC (major histocompatibility complex proteins) class I molecules upon their surfaces, so that T cells surveying the area can identify and eliminate the viral infection. Viruses are highly adaptable, and have developed ways to avoid detection by T cells. Some viruses stop MHC molecules from getting to the cell surface to display viral peptides. If this happens, the T cell doesn’t know there’s a virus inside the infected cell.
But we should know that the first line of defence is to prevent infection from entering the body.
(The writer can be reached at [email protected])
KV Network
