What to watch out for after Covid-19 infection

WITH the pandemic sweeping across the globe, millions of people have been infected with the Covid-19 virus and have recovered from the infection. However, it has become apparent that in some patients, symptoms tend to persist despite the absence of any evidence of active infection. This has given rise to the term "long Covid" to denote the condition where patients have persistent symptoms after recovering from the infection.

There is no universally agreed definition of long Covid.

In the United States, the Centers for Disease Control and Prevention (CDC) defines long Covid as a wide range of new, returning, or ongoing health problems people can experience 4 or more weeks after first being infected with Covid-19. As of July 2021, long Covid is considered a disability under the Americans with Disabilities Act.

In the United Kingdom, long Covid refers to symptoms continuing for more than 12 weeks after a Covid infection which cannot be explained by another cause.

In October this year, the World Health Organization (WHO) published a definition of long Covid as follows: "Post Covid-19 condition occurs in individuals with a history of probable or confirmed SARS-CoV-2 infection, usually 3 months from the onset of Covid-19 with symptoms that last for at least 2 months and cannot be explained by an alternative diagnosis."

The proposal of Post Covid-19 condition (PC19) as the officially recognised name for this issue by WHO's International Classification of Diseases marks a major milestone in recognising it as a distinct medical entity.

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Lingering symptoms

The WHO estimated that 10 per cent to 20 per cent of Covid-19 patients have lingering symptoms for months following infection and are considered as having PC19. The common symptoms of Post Covid-19 condition as described by WHO, CDC or the UK's National Health System (NHS) include extreme tiredness, shortness of breath, heart palpitations, chest pain or tightness, problems with memory and concentration ("brain fog"), changes to taste and smell, joint pain, abdominal pain, diarrhoea, insomnia, and changes to menstrual cycle.

While the symptoms may be mild for some, on the other extreme, patients with severe PC19 symptoms may be unable to perform routine tasks such as showering, grocery shopping and remembering words.

According to CDC, it is difficult to ascertain whether these symptoms are mainly attributable to Covid-19 infection or other causes related to long- term hospital stay.

Prolonged hospitalisation can also lead to post-intensive care syndrome (PICS), which is a condition with symptoms of impaired cognition (such as memory, thinking, concentration, organisation), emotional disturbances (such as anxiety, depression, decreased motivation post-traumatic stress disorder) and physical deterioration (difficulty in breathing, fatigue, muscle weakness, insomnia) which commence after the onset of the critical illness and persist after discharge from the ICU. The symptoms can last for varying periods lasting from weeks to years.

Post Covid-19 condition risk

Current data seems to suggest that the risk of PC19 increases with age and women are twice as likely as compared to men to develop PC19. Those with severe illness and hospitalisation are also more likely to develop PC19.

Post Covid-19 condition  in children

Children are less likely to get Covid-19 infection than adults. The American Academy of Pediatrics and the Children's Hospital Association collects state-level data across the US. As of Oct 28, 2021, nearly 6.4 million children have tested positive for Covid-19 since the onset of the pandemic and depending on the state, 0.1 per cent to 2.0 per cent of all the child Covid-19 cases resulted in hospitalisation. In states that were reporting their data, 0.00 per cent to 0.03 per cent of all child Covid-19 cases resulted in death. In Singapore, as of September 2021, no child had developed severe illness requiring oxygen supplementation or ICU care.

While all children can potentially get the Covid-19 virus, most children have no symptoms or mild symptoms. However, babies under age 1 might be at higher risk of severe illness with Covid-19 as compared to older children. This may be due to their immature immune systems and smaller airways in their lungs, increasing their vulnerability to developing lung problems following Covid-19 infection.

There is evidence to suggest that children who develop serious Covid-19 infection are more likely to have underlying medical conditions such as genetic diseases, neurological conditions, congenital heart disease, obesity, diabetes, asthma, chronic lung disease, sickle cell disease, or immunosuppression.

Although the likelihood of serious outcomes following Covid-19 infection is extremely low in children, nevertheless the development of long Covid in children is an area of concern.

A recent September 2021 publication on the Children and Young People with Long Covid (Clock) study by University College London, Great Ormond Street Institute of Child Health, reported that 1 in 7 children between the ages of 11 to 17 years may still have symptoms 15 weeks after Covid-19 infection. The most common symptoms reported were headaches and tiredness.

Cause and diagnosis of Post Covid-19 condition

All the current definitions used by the WHO, CDC or NHS state that the diagnosis of PC19 is made where there are no other alternative diagnosis - that is, the diagnosis of PC19 is a diagnosis of exclusion.

Current research suggest that Covid-19 infection can cause the generation of "rogue" elements within the body's immune defence system in some patients. These rogue antibodies or autoantibodies can turn against the body's cells attacking specific proteins on the cells in the body and disabling some of the defensive responses. Some researchers have suggested that the persistence of these rogue elements may contribute to the persistence of symptoms despite the absence of viral particles in the patient. The presence of these rogue autoantibodies have been associated with the development of severe Covid-19 disease. As more data becomes available, researchers may be able to use diagnostic tests to find out these rogue autoantibodies for identifying those with PC19 in the future.

In a November 2021 presentation at the Society for Neuroscience meeting in the US, researchers at the Rotman Research Institute in Toronto used electroencephalography, or EEG, to measure brain function. The study showed that the brain waves in patients with Covid-19 infection were different and these changes lasted for at least 7 months following their initial infection.

This finding provides supportive evidence that Covid-19 infection can affect brain function. Hence, as doctors learn more from ongoing Covid-19 research, diagnostic tools can be made available to diagnose those with PC19 more readily.

Vaccination in Post Covid-19 condition

Vaccination appears to be beneficial for those with PC19. In a Sept 29, 2021 early stage publication in the Lancet journal, researchers from the Community of Patients for Research (ComPaRe) long Covid cohort study reported that vaccination leads to an improvement in symptoms among patients with long Covid. By 120 days post vaccination, 16.6 per cent of patients in the vaccination group reported a remission of all symptoms from long Covid, which was compared with 7.5 per cent in the control group.

There appears to be light at the end of the tunnel for PC19 patients who suffer from the lingering symptoms of this condition as more diagnostic tools are being developed.

Most importantly, the best treatment for PC19 is the prevention of Covid-19 infection with vaccination.

• This article is produced in collaboration with Royal Healthcare Heart, Stroke & Cancer Centre