On December 31, 2019, China reported to the World Health Organization (WHO) about a mysterious virus causing pneumonia outbreak in the country. Nothing much was known about the virus; it did not even have a name. But what scientists and medicos could perceive was an extraordinary health threat which eventually engulfed the entire world.
Within two weeks, Chinese scientists were able to decipher the genome sequence of the novel coronavirus and within a few weeks, the first test kit was made. Now, as the year ends, some people have already received the trial vaccines. Amid the worldwide panic, scientists have worked with remarkable and unprecedented speed.
Nevertheless, there still remain some crucial aspects of the disease and the virus that await solid scientific conclusions.
Why does severity vary across cases?
The reason behind the wide distribution of the symptoms of COVID-19, starting from asymptomatic to those requiring medical ventilation, still remains to be fully understood. As per research, age and pre-existing medical conditions are common risk factors for those who are severely ill and men are at a higher risk than women, primarily because of the immune system.
However, one major commonality is the severe inflammatory response. The body’s own immune system gets out of track and unleashes inflammatory attack on own organs while trying to target the virus in a misguided attempt. The hyper reactive immune response is one of the key problems that a majority of the severely ill patients have to face.
In a paper published in Nature in August, researchers found that two crucial proteins of the early immune response, the TNF alpha and interleukin 6. The higher degree of presence of these two could be a marker to predict whether a patient will suffer from serious illness or even die. The study comprised of 1,500 hospitalized patients.
Again, asymptomatic or mildly symptomatic patients are the most confusing cases. What makes some people asymptomatic to infection is not well understood. However, scientists are looking into the possibility of a pre-existing immunity of previous coronavirus exposure (other than SARS-CoV-2) that causes common cold. The memory T cells developed in such cases are believed to offer some immunity in some patients.
Regarding the infection in children, one aspect observed is that children tend to have a less serious infection. This may pertain to the lesser number of ACE2 receptors in the noses of the children. The ACE2 receptor is the gateway through which the SARS-CoV-2 makes an entry into the cells.
The long-term effects of infection
Although it has become clear that in some patients, COVID-19 can have prolonged health impacts, there is no widely-agreed definition of some terms like long COVID or post-COVID syndrome. However, the major symptoms that linger after an infection include heart abnormalities, brain function disruption, fatigue and breathing problems. Notably, these problems are not necessarily associated with an initial severe illness.
A study published in British Medical Journal estimated that about 10% of COVID-19 patients could have prolonged health effects that could extend up to 12 weeks.
One of the large cohort studies of 4,182 infected people found that 13.3% had symptoms for more than four weeks, 4.5% for eight weeks and 2% for a long period of 12 weeks. However, what long-term effects could be present in recovered people is still not well understood and also what fraction of the recovered patients will have long-term effects is yet unanswered.
How long will natural immunity last?
The immune system can effectively produce neutralizing antibodies and also memory T cells to fight the SARS-CoV-2 virus. But what exactly could be the duration of this natural immunity is still an open question. One reason for this is that the virus has been around for a limited time, restricting the period of study.
There have also been cases of re-infection which challenge the notion that natural immunity could exist for at least six months as suggested by some studies. For example, in the Hong Kong case, which was the first documented case of re-infection, the person was re-infected within four and a half months of the first infection.
Further, how frequent or common the re-infection levels are remains unclear as there are only few such documented cases. Studies are ongoing to find out the frequency of re-infections and if they are any different than the first incidence. Aubree Gordon of University of Michigan, an epidemiologist, is among those who have undertaken such studies.
The origin of the virus
Meanwhile, there have been a number of conspiracy theories as well as certain misconceptions regarding the origin of the novel coronavirus. As per one such conspiracy theory, the virus was engineered in a Chinese lab and released to the world. Even Donald Trump questioned whether the virus was created in the Wuhan lab and released to the rest of the world from there.
Another theory was that it was linked to the Wuhan meat market that sells live animals. However, a Lancet study found that one third of the patients infected during the early period of the outbreak did not have any direct link to the market. Scientists say that there is ample evidence that the virus originated in the wild.
There are also studies that say that the virus may have been circulating in the US and Europe in December 2019.
Despite all the conspiracy theories, scientists believe that the virus is zoonotic, meaning that it originated in an animal. Many scientists believe that bat is the most likely species where the virus originated and eventually jumped to humans. However, what remains unclear is where exactly the virus passed on to humans and whether it did so via an intermediary species like a pangolin or a civet.
When will the pandemic end?
Of all the questions around the pandemic, the biggest is when the pandemic will come to an end. The quest for vaccines plays the most important role here as it is considered as the foremost weapon against the virus. The research for a potential vaccine has progressed at a remarkable speed in the history of modern medicine and some people have already even been vaccinated. Yet, there are still questions unanswered about the nature of immunity that these vaccines can provide. Further, worldwide vaccination itself will take more than a few years.
Also, it should be noted that only one virus has so far been completely eliminated through vaccines, i.e., small pox.
The viral mutation is also likely to play an influential role in the entire dynamics of the pandemic. Any mutation can render a pathogen with an edge in terms of spreading while on the other hand, it can also make a virus weaker. The recent UK strain is has been reportedly found to be more contagious than the earlier strains. So, the possible future strains of the virus can also impact vaccine functioning.
