For most people, Covid-19 is a brief and mild disease but some are left struggling with symptoms including lasting fatigue, persistent pain, and breathlessness for months.
The condition is known as "long Covid" which is having a debilitating effect on people's lives, and stories of being left exhausted after even a short walk are now common. This condition can affect anyone including healthy young adults and even children. So far, the focus has been on saving lives during the pandemic, but there is now a growing recognition that people are facing long-term consequences of a Covid infection.
Yet even basic questions - such as why people get long Covid or whether everyone will fully recover - are riddled with uncertainty.
There is no medical definition or list of symptoms shared by all patients - two people with long Covid can have very different experiences. However, the most common feature is crippling fatigue. Other symptoms include breathlessness, a cough that won't go away, joint pain, muscle aches, hearing and eyesight problems, headaches, loss of smell and taste as well as damage to the heart, lungs, kidneys, and gut. Mental health problems have been reported including depression, anxiety, and struggling to think clearly.
Long Covid is not just people taking time to recover from a stay in intensive care. Even people with relatively mild infections can be left with lasting and severe health problems. "I think what's more interesting in long COVID is a number of people that only got relatively mild disease” said Prof. David Strain, from the University of Exeter, who has been seeing long-Covid patients at his Chronic Fatigue Syndrome clinic.
Symptoms of Long COVID
People may have one or multiple symptoms and this collection of symptoms can change over time and vary in intensity.
A study of 292 people in the US showed that 35% of non-hospitalised people testing positive for COVID-19 had not returned to their previous health within four weeks. Ongoing research by the UK Office of National Statistics shows that 20% of adults and 12-15% of children have symptoms that persist for 5 weeks or longer, with 10% of adults showing symptoms for over 12 weeks. The ONS data contains both people with mild and severe (or hospitalized) cases of COVID. However, the persistence of symptoms in previously hospitalised patients appears to be greater, with a report from the UK suggesting that 89% of patients experience persistent symptoms at 8 weeks and a report from Spain suggesting that 50% of patients were still experiencing symptoms between 10-14 weeks after infection. Though a survey in the US showed similar rates of persistent symptoms between hospitalised and non-hospitalised patients 6 months after infection (33% for non-hospitalised and 31% for hospitalised patients).
It appears not.
Half of the people in a study in Dublin still had fatigue 10 weeks after being infected with coronavirus. A third were physically unable to return to work. Crucially, doctors found no link between the severity of the infection and fatigue. However, extreme exhaustion is only one symptom of long Covid. Research in the US looking at 73,435 patients 6 months after COIV-19 diagnosis showed that patients who had been hospitalised had a greater likelihood of experiencing any individual symptom than those with milder infection. Risks were further elevated in patients that had required intensive care during their hospitalisation. While many people with mild cases develop persistent symptoms, severe infections seem to increase the risk of long-term disease. Prof Chris Brightling, from the University of Leicester and the chief investigator in the PHOSP-Covid project which is tracking people's recovery, believes damage that occurred during the virus infection may be the cause of some of the symptom persistence. For example, people who developed pneumonia may have more problems because of damage to the lungs.
There are lots of ideas, but no definitive answers. The virus may have been cleared from most of the body, but continues to linger in some small pockets." If there's long-term diarrhea then you find the virus in the gut, if there's loss of smell it is in the nerves - so that could be what's causing the problem," says Prof Tim Spector, from King's College London. The coronavirus can directly infect a wide variety of cells in the body and trigger an overactive immune response which also causes damage throughout the body. One thought is the immune system does not return to normal after Covid and this causes ill-health. The infection may also alter how people's organs function. This is most obvious with the lungs if they become scarred - long-term problems have been seen after infection with SARS or MERS, which are both types of coronavirus.
But Covid may also alter people's metabolism. There have been cases of people struggling to control their blood sugar levels after developing diabetes as a result of Covid, and SARS led to changes in the way the body processed fats for at least 12 years. There are early signs of changes to the brain structure, but these are still being investigated. And Covid-19 also does strange things to the blood, including abnormal clotting, and damaging the network of tubes that carry blood around the body.
Post-viral fatigue or a post-viral cough are well documented and common - we've probably all had an infection that has taken ages to fully recover from. Around one in 10 people with glandular fever has fatigue which lasts for months. 70% of Ebola virus survivors report persistent symptoms over two years later. There are also some preliminary suggestions that some flu infections (like bird flu and the 1918 Spanish flu pandemic) may be linked to Parkinson's-like symptoms. "With Covid, there seem to be more far-reaching symptoms and the number of people seems to be much greater," says Prof. Brightling of the University of Leicester.
The emphasis though is on the word "seems" as until we have a true picture of how many people have been infected we won't know exactly how common these symptoms are, he says.
He said "The uniqueness of the way the virus attacks the host and the different ways it then alters the way cells behave seem to be both giving people more severe infection than other viruses and persistent symptoms."
· SYMPTOMS: 85% of patients have one of these three symptoms
· IMMUNITY: Can you catch it twice?
The NHS has a "Your Covid Recovery Plan" which has advice, particularly for those who needed hospital treatment.
It recommends the "three Ps" in order to conserve energy:
· Pace yourself - don't push yourself too hard, and make sure you have plenty of rest
· Plan your days so your most tiring activities are spread out across the week
· Prioritize - think about what you need to do and what can be put off
It advises speaking to either your hospital team or your GP if you are not recovering as quickly as you might expect. The NHS has also created a Living Review on the scientific information pertaining to long-Covid.