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such as permanent damage to the vital<br />
organs such as the lungs and heart,<br />
post-intensive-care syndrome, post-viral<br />
fatigue syndrome or continuing COVID-19<br />
symptoms.<br />
Many hypotheses are going around,<br />
claiming to explain the strange phenomena<br />
of long-lasting COVID symptoms. Some<br />
theories propose that the wide distribution<br />
of angiotensin-converting enzyme 2 (ACE-<br />
2), the cellular receptor that SARS-CoV-2<br />
uses to enter the host, is partly responsible<br />
for the extent of the damage.<br />
However, most recent research<br />
squarely blames a hyperactive immune<br />
system triggered by the coronavirus for<br />
the devastating effects. Studies have<br />
observed very high levels of inflammatory<br />
cytokines (cytokine storm) in the blood of<br />
hospitalized patients with severe COVID-19.<br />
Excessive inflammation can lead to<br />
collateral damage and worsen pre-existing<br />
conditions.<br />
Others think that the symptoms result<br />
from post-viral autoimmunity and the<br />
consequences of thrombotic complications.<br />
Besides causing abnormal clotting,<br />
COVID-19 damages the microvasculature<br />
systems too.<br />
Researchers at Yale suggest three<br />
possible reasons for the long-term effects<br />
of COVID-19. Patients with long-term<br />
symptoms might still harbour the<br />
infectious virus in some reservoir organ,<br />
not identified by nasal swabs. The second<br />
possibility is that persistent fragments<br />
of viral genes, though not infectious,<br />
may be triggering an exuberant immune<br />
reaction. Thirdly, even after clearing the<br />
virus from the body, the immune system<br />
may continue to be in an overactive<br />
or perturbed state, similar to the one<br />
observed after glandular fever.<br />
At times, the virus can cause parts of<br />
the immune system to become overactive<br />
and trigger harmful inflammation<br />
throughout the body. This is well<br />
documented in the acute phase of the<br />
illness. This mechanism is also implicated<br />
in some of the short-term impacts<br />
of the infection. Immune overreaction<br />
can also happen in adults with severe<br />
COVID-19.<br />
The side effects of intensive treatments<br />
such as intubation may also be behind<br />
some of the damage. Patients experience<br />
injury to muscles or the nerves that supply<br />
them. But what is interesting is that the<br />
long-term symptoms are not limited to<br />
people who stay in intensive care with<br />
severe illness, but are also found in those<br />
with relatively mild infections.<br />
Researchers are grappling with each<br />
and every theory and hypothesis to unravel<br />
the mysteries of the strange virus.<br />
Currently, many large medical centers<br />
are opening specialized clinics to provide<br />
care for people who have persistent<br />
symptoms or related illnesses after they<br />
have recovered from COVID-19.<br />
<strong>December</strong> <strong>2020</strong> / FUTURE MEDICINE / 37
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