With each passing day newer insights into COVID-19 are being reported. Over a period of one year we have gained some knowledge regarding the transmission and prevention of this disease, however, a lot still needs to be established to successfully curb the pandemic. In this article, let us focus on some of the confirmed aspects of the disease and also the doubtful ones which require further research.

5 established facts

Airborne transmission

Several studies have published reports that the transmission of coronavirus is airborne via the release of the virus in microdroplets during exhalation, talking, sneezing or coughing. These infected droplets can remain suspended in the air before settling down and thereby increase the risk of infection. The disease spreads via respiratory droplets in face-to-face contact. In addition, it has been reported that prolonged exposure of atleast 15 minutes (within 6 feet) with an infected person increases the risk of transmission.

Increased mortality rate with advanced age and presence of comorbidities

Advanced age is a risk factor for mortality in COVID-19 infection and approximately 80% of the deaths have been reported in people more than 65 years of age. This could be due to weakening of the immune system with ageing. Diabetes mellitus has been established to be associated with higher mortality risk in COVID-19 infection. Reduced innate immunity and chronic inflammation in diabetes mellitus could be responsible for the increased mortality. Other comorbidities increasing the mortality rate in COVID-19 infection are hypertension, presence of cardiovascular disease, bronchial asthma, chronic obstructive pulmonary disease (COPD), malignancy and chronic renal and liver diseases.

Control measures need to be continued or else outbreaks return

It has been reported in several countries that relaxation of the strict control measures can result in outbreak of COVID-19 infection. Therefore, most of the governing authorities recommend adherence to preventive measures to contain the disease and prevent its spread.

Antivirals and steroids for management

Anti-viral remdesivir has been shown to fasten the time to recovery from 15 to 11 days. Hydroxychloroquine has been proven to be effective due to its anti-viral, anti- inflammatory and anti- thrombotic effects. As per the Indian guidelines, hydroxychloroquine is recommended even in mild cases of COVID-19 in the presence of co-morbidities. Dexamethasone has reported to reduce the risk of mortality in patients with COVID-19. However, Indian guidelines do not recommend routine administration of systemic corticosteroids due to the associated adverse effects.

Preventive measures should be practiced post vaccine administration too

Masks, social distancing, washing hands: Since the mode of transmission of the disease has been proven to be airborne, maintaining a distance of approximately 1-2 meters (3-6 feet) has been suggested by experts for prevention of disease transmission. Based on the available evidence, mandatory use of masks is promoted by the governing authorities of several countries to prevent spread of the disease by asymptomatic patients. Hand hygiene practices such as frequent hand washing with soap and water for 20 seconds is recommended to prevent transmission by contaminated hands and thereby break the chain of disease transmission. Hand sanitisation using alcohol based sanitisers are also recommended to prevent infection.

5 things that are yet to be confirmed

How long the immunity lasts

The duration of acquired immunity in COVID-19 infection is yet unknown. Due to its resemblance to the other seasonal coronaviruses that cause respiratory tract infection, it is predicted that the immunity against COVID-19 infection is short lived upto a duration of one year after which the risk of reinfection increases.

Vaccine competency

Currently there are two vaccines approved for use in India namely, Covaxin and Covishield. Covaxin is Whole Virion Inactivated Corona Virus Vaccine. Phase III clinical trials on this vaccine established the safety and efficacy of the vaccine. Covishield is a Recombinant Chimpanzee Adenovirus vector vaccine encoding the SARS-CoV-2 Spike (S) glycoprotein. Indian regulatory authorities have permitted restricted use of both these vaccines in emergency situation. There are several other vaccine candidates under investigation; however the superiority of one vaccine over the other is still unknown.

Long term effects

It is still premature to predict the long term complications and sequelae of COVID-19. However, there are reports of complications such as organ dysfunction especially in heart, lungs and brain. These complications could be due to direct effect by the virus, intense inflammation, cytokine storm, immune system damage and hypercoagulability associated with COVID-19 infection.

How long do the symptoms last; What is “long COVID”?

It is seen that normally the incubation period of the virus is 2 to 14 days and the symptoms last for 1-2 weeks. However, some patients continue to be symptomatic even after recovery from COVID-19, which is known as “Long COVID”. In this condition, the patients do not have fever or signs of acute illness, but complain of fatigue, dyspnoea, joint pain and chest pain. As a result, the patients may have difficulty to carry out their occupational activities adversely affecting their quality of life.

How long does the immunity last?

The duration of acquired immunity in COVID-19 infection is yet unknown. Due to its resemblance to the other seasonal coronaviruses that cause respiratory tract infection, it is predicted that the immunity against COVID-19 infection is short lived upto a duration of one year after which the risk of reinfection increases.

Based on the available evidence, it is apparent that though we have some data regarding this disease, we still have a long way to go until we get comprehensive knowledge about the pathogenesis, prevention and management of the novel COVID-19 infection.