Scientists say while known incidences of reinfection appear rare, cases are worrying.
Across the globe, doctors, researchers and scientists are working around the clock to investigate the ways COVID-19 affects the human body – and there is a lot we are still learning.
Recovery time for those with COVID-19 varies. This is due to a number of factors, including whether a patient has underlying or associated chronic conditions, whether they have a mild or severe case, and whether or not they become critically ill.
Anecdotally, we know that the more critical a case is, the longer the duration of the illness. For severe cases that required hospitalisation, the average amount of time spent undergoing hospital treatment is between seven and 14 days. But for those who become critically ill, needing to go on a ventilator or into intensive care, this number may increase to between 30 and 40 days.
For those with mild symptoms, meaning they did not need hospital care, most experience a shorter illness and recover quickly. However, there are now reports of some people even with mild disease who continue to experience persistent symptoms, and do not return back to usual health – even months later.
If a patient has a mild illness, they usually experience symptoms such as a fever, cough, sore throat, fatigue and, in some cases, loss of smell or taste.
If a patient is critically ill, that usually means their respiratory system is not working or they have other organ problems – such as severe pneumonia, acute respiratory distress syndrome or sepsis, which can lead to multi-organ failure. In other words, the patient’s body is malfunctioning.
Critical patients may experience prolonged viral shedding – which is the period when the virus is detectable and potentially transmissible. But even if they are no longer infectious with SARS-CoV-2, their critical illness can be prolonged. It is likely that these patients are having an abnormal immune system response, which causes inflammation and injury to the cells lining the small blood vessels, tissue swelling, and injury to the organs themselves.
In the lungs, for example, this injury is called Acute Respiratory Distress Syndrome (ARDS). It develops as a result of injury to the cells lining the lung’s air sacs and the cells lining the small vessels (endothelium) that bring blood to the lungs for oxygen. This causes fluid and proteins to fill up the air sacs, and the injury to the endothelium can activate blood clotting, tissue swelling and low blood oxygen levels.
COVID-19 is known to be a respiratory disease. So how does it cause organs to malfunction and fail? The answer can be found in a life-threatening condition called sepsis.
When faced with any infection, the body and the immune system reacts. But if an infection becomes severe, it can cause an abnormal immune response – like sepsis. If this happens, it is not the infection itself causing problems, but rather the body’s response to the infection, which causes injury to its own tissues and organs.
In some patients with a severe or critical case of COVID-19, the virus makes them sick, invades their lungs and causes severe pneumonia. In some patients, as their body tries to fight the infection it may overreact, and they develop sepsis. The combination of sepsis and COVID-19 means it is no longer just pneumonia in the patient’s lungs. Pneumonia will be there, but the additional abnormal immune response – the sepsis – can cause tissue damage, multi-organ failure and even death. Immunosuppressed people – patients with chronic diseases – are more likely to get sepsis than patients with a normal immune system.
To prevent sepsis from occurring, an effective COVID-19 vaccine is needed, or an antiviral treatment – which is an agent that suppresses a virus’s ability to replicate. But as yet, there are no approved options, so we cannot intervene against the virus in these ways.
Another approach is to modulate a patient’s immune system, asking what we can do to stop the abnormal immune response from causing damage. Steroids, like dexamethasone or hydrocortisone, have shown promise in this regard. They reduce mortality in patients with severe or critical COVID-19. However, if taken for mild cases, steroids do not work and may cause harm and even death.
In the absence of a viable vaccine and while other therapeutics are being tested, supportive care becomes the mainstay from the moment a patient shows the first signs of distress or severe symptoms, signalling that they need an intervention.
One of the first signs can be fast breathing and low oxygen levels, meaning the patient should get oxygen immediately. In patients who are critical, oxygen may need to be delivered via a ventilator or other higher-flow oxygen support systems. Without enough oxygen being pumped around the body via the bloodstream, the body’s cells get more damaged and this may cause the organs to fail faster.
One of the items on the WHO’s Essential Medicine List, oxygen is life-saving and countries should ensure their hospitals have an adequate supply. Good, optimised supportive care that helps maintain the patient’s oxygen level and blood pressure will hopefully allow the body to heal itself. After the organs have healed, the patient can be taken off supportive care so they can recover naturally.
There is still a lot we are learning about COVID-19, but the main symptoms and deficits we are watching out for in the long term are respiratory, neurological, cardiac and physical.
First, we have to monitor former patients to see if the lungs heal and return to their pre-coronavirus state. Next, we must pay attention to neurological problems – psychological or psychiatric concerns, including depression and anxiety, but also poor concentration and complications such as a stroke. Finally, we need to pay attention to a patient’s physical mobility. After weeks in a hospital bed without much movement, the muscles and joints are affected, so we have to track any physical limitations.
Other than these three main areas, we need to monitor any organs that were affected while the patient was in hospital – such as the heart for those who developed cardiac issues. We need to watch to see whether those who experienced heart troubles while in hospital have similar problems later. We know now, that some patients with mild disease, can also experience persistent symptoms such as fatigue, shortness of breath, or headaches and not return to their usual health. Post-COVID-19 disorders need to be better understood.
The long-term immune response to the virus is also something we are slowly figuring out. It is still unclear how much immunity a person has after being infected, how different the immune response is for those who had mild, moderate and severe cases, and how long the immunity will last. Immune responses are complicated, as is our immune system – there is a lot we all still need to learn.