Although we only became aware of Covid-19 (SARS-Cov-2) in early 2020, scientists and researchers have now traced back to its early origins.
Coronaviruses are widespread among many different mammals. SARS-Cov-1 came to humans from the Asian civet. Middle Eastern Respiratory Syndrome (MERS) came via dromedary camels. Covid-19 came directly from horseshoe bats.
Around the world, scientists have been studying coronaviruses for some years, in order to better understand how they function and how to develop vaccines against them. To do this they deliberately try to make existing microbes more infectious or deadly. This 'gain-of-function' research is used to work out well before it happens in nature (a) which viruses are likely to cause pandemics and (b) develop ways to stop this happening.
While no serious scientist is claiming that such an engineered virus has been deliberately released, some are concerned that there may have been an accidental release. They note that the Covid-19 virus has multiple odd characteristics which make it well adapted to humans, while poorly adapted to bats, which are thought to be the original host species. Other scientists feel a natural origin is much more likely, and the 'lab leak' theory underestimates the power of natural selection.
Whichever of these views is correct we may never know. However to avoid the risks for future, serious bio-leaks, it is important that these labs operate with open scrutiny and accountability.
When did the virus first infect people?
In 2012, six mine workers in China had Covid-like symptoms after visiting a bat cave, but it seems no reports identified the cause.
2019 Nov.: Three researchers from the Wuhan laboratory fell ill around the time the pandemic appears to have begun.
In many countries, including the UK, the variety of virus mutations identified during early sampling was almost as great as the variety seen across the whole world. This suggests that the virus entered the UK many times independently, rather than via any one 'patient zero' case that seeded the UK national epidemic.
2019 Dec. 31: Chinese authorities notified the World Health Organisation (WHO) of a new and dangerous viral form of pneumonia recently found in Wuhan. At this point it had no name.
2020 Jan. 13: UK health bodies notified GP practices describing the new virus. As there were only three flights from Wuhan to the UK each week, the likely impact was estimated to be Very Low.
2020 Jan. 20: With rapidly rising infections , the Chinese Health Commission confirmed it could spread between humans. At this time the Lunar Holiday season meant around 2 billion trips were made by people visiting families. On the 24th, train and plane journeys were cancelled to and from Wuhan. The process of lockdown had begun.
2020 Jan. 29: First confirmed cases in the UK were a Chinese couple staying in York. UK health bodies started to advise travellers from Wuhan to the UK to self-isolate for fourteen days, even if they had no symptoms.
2020 Feb. 5: WHO confirms there is no known effective treatment. It was becoming obvious that the virus was spreading rapidly, with many people showing no symptoms, which made isolating affected people more difficult. Later in Feb., France, Italy and Spain all reported cases, including within country infection.
2020 Mar. Many people returning to the UK from skiing holidays were coming down with coughs and fevers. Limited testing masked the true infection rate. Mar. 5. First UK death. Mar. 17: People advised to avoid going out, and self-isolate if anyone in a household had symptoms. Mar. 18: Schools closed.
SARS-Cov-2 now designated a pandemic by WHO.
2020 Apr. Now clear that for most people the virus irritates the upper airway, producing a dry cough, loss of taste and smell, and fever. Many have headaches, while for a few, the virus attacks the digestive tract. Four out of five start to recover after 4 or 5 days. In the rest (mostly middle-aged or over, overweight and male) , the virus attacks the lung tissue and treatment was limited.
2021 June. Now the most commonly reported symptoms are a cough, headache and fatigue. It is likely that this is due to the virus infecting younger and healthier people who have strong immune systems. But given the rate of spread of the Delta variant, it's possible many people believe they have a cold or hay fever, potentially putting others at risk of infection.
Herd immunity: The Delta variant is far more infectious than previous variants, so a higher rate of population immunity (85%) is needed to stop it spreading. This cannot be achieved by only vaccinating the adult population, and at least some of the under-18s will need to be vaccinated.
Impact on NHS: June 2021 Covid infections are at the same level at mid-December 2020, when hospitals were overwhelmed with severe cases and many deaths, but far fewer people now need hospital treatment and very few die, since the majority of current cases are in younger groups who have less risk of getting seriously ill. If more elderly people get infected, hospital cases (and deaths) will rise.
Long Covid June 2021: Office of National Statistics survey show more than one million Britons are currently suffering from long Covid, with two-thirds of these having symptoms that impact on daily life. Early studies suggest that vaccines cut the risk of long Covid by around 50 per cent.
ACE-2 cells: Identified that Covid-19 binds frighteningly well to ACE-2 cells, which help regulate blood flow through body tissues. Men have more ACE-2 coating their cells, and children much less. This partly explains the pattern of (especially older) men often suffering more severe infections and children having minimal symptoms. Other factors such as poor housing, multi-generational living, and working in high contact jobs (care home assistants, cleaners and porters in hospitals) prior to wearing protective clothing are likely to account for the black, Asian and other ethnic minorities suffering more severely.
Community lockdowns were effective in slowing transmission, and therefore reducing hospitalisations and deaths. But we don't see immediate benefits as some people are already infected (and passing the virus on to others) before they show symptoms.
Main source: Intensive Care: a GP, a Community & Covid-19 by Gavin Francis, Profile Books, 2021.
