By Dr. John Morgan
One hundred year ago the nursery rhyme “I had a little bird, and its name was Enza. I opened the window and in flew-Enza” was often sung by children while skipping with a rope. It had its origins in the great Flu Pandemic of 1918-1919. The 1918 Influenza pandemic, mistakenly called the Spanish Flu, killed an estimated 50 million people globally over the course of about a year, 1 in 40 people. Remember the global population was about 2 billion in 1918 compared to 8 billion today. This virus emerged suddenly. The best scientific evidence is that it was a bird flu virus that mutated and evolved to very successfully infect humans. Flu is interesting as the 3 main sources of influenza viruses are humans, pigs and aquatic birds and it is this complex and unpredictable interplay that usually leads to the emergence of a new ‘mosaic’ virus containing a mix of genes from all 3 viruses. This can then lead to a new flu pandemic. Our immune system will have never encountered this new virus before and as a result we are very susceptible to infection for a period of time.
Within 2 or 3 years the 1918 flu virus more or less disappeared, it had infected as many people as it could and it ran out of victims. The world’s population had reached ‘Herd Immunity’ to the virus. People wanted to quickly forget about the flu and get on with life, a well documented collective amnesia occurred. It was 1957 before a new flu pandemic occurred with the emergence of a new flu virus, the ‘Asian flu’. For most people living today the first they are likely to have heard of the great human catastrophe of 1918 was when comparisons were made between it and Covid-19.
Covid-19 emerged in China probably towards the end of 2019 and many types of coronavirus are known to circulate in wild bat populations. SARS coronavirus emerged in China in 2003 but luckily the authorities brought that infection under control in time and there have been no more cases. No such luck with Covid-19! What is known is that Covid-19 is very closely related to a bat coronavirus and it has evolved to very successfully infect humans. The virus has evolved to produce genetic changes to a protein on its surface, the Spike protein, making it very efficient at infecting human cells. The virus Spike protein binds to an ACE2 receptor on the surface of our cells. ACE2 is present on the surface of cells in many of our organs, not just in our lungs but the heart, kidneys and intestines. This makes it a very dangerous infection with multiple target organs and subsequent potential long-term organ damage. A lot has been learned about Covid-19 since the start of this year. The genetic makeup of the virus is being analysed daily with very little evidence of any changes in its makeup. Viruses can with time become weaker, a process known as attenuation, but this seems unlikely with Covid-19 in the short term. We will need better ways to control and treat this infection.
Treatments and Vaccines
Some existing drugs that control clotting and steroids that dampen down the immune system appear to be making an impact on reducing the severity and death rates from COVID-19. We know that antibodies can neutralise the virus. Very soon we will have Monoclonal Antibodies that can be used to help infected patients. Monoclonal antibodies are examples of a new type of biological drugs, known as a ‘Biologics’, being developed by the Biotechnology industry. Regeneron, in Limerick, are world leaders in this area and this technology has already been used to produce biological drugs to target and treat many cancers. President Trump did receive an infusion of two Regeneron antibodies after testing positive for COVID-19.
Targeting Covid-19 with very specific antiviral drugs to inhibit or block the ability of the virus to replicate are in development. Antiviral drugs developed in recent years have dramatically improved the treatment of HIV and Hepatitis C patients. Nowadays most HIV infected patients can expect to live close to a normal lifespan and a high percentage of Hepatitis C patients can now be cured of the infection.
The secret to controlling this virus is herd immunity. This is a measurement of the level of immunity that must build up in the population to ensure a high level of protection into the future. Epidemiologists believe that greater than 60% of the population will need to reach Herd Immunity to protect those susceptible to the most severe outcomes of infection with Covid-19. This level of herd immunity will be very difficult to achieve through natural infection. The best estimates, from antibody studies, is that maybe at best 5% of the population have been exposed to this virus up to this point in time. Some people believe that the virus should be let ‘rip loose’ through the population, the argument being that you could achieve immunity in most of the younger population with less severe outcomes. This is debatable. The problem with this argument is that young people have older relatives or know people with underlying medical conditions. How can they be safely protected? For most modern societies like ours who value protecting its citizens this is a risk they are not willing to contemplate. However, a balance needs to be struck to help avoid other human suffering, lost livelihoods and damage to the economy.
The other way of achieving mass herd immunity is through vaccination. Vaccines have proving very effective in fighting infections over the last 100 years. They have helped to dramatically reduce mortality rates for many infant and childhood infections. Smallpox, a scourge of humanity for centuries, was eradicated from the planet in 1977 through vaccination and the elimination of poliovirus is now within touching distance. The function of a vaccine is to trick the immune system into thinking it is been infected with the real virus and thereby develop protective immunity to future exposure to the virus. The scientific and medical community are quietly confident that safe and effective vaccines will be developed. Some 40 different vaccines are at different stages of development using many novel approaches. The evidence from other coronavirus infections is that immunity is likely to last only a few short years at best. However, this would certainly be a good start, Covid-19 vaccination may ultimately need to be administered as often as yearly until the pandemic is under control. There will be great logistical challenges, how can enough vaccine be manufactured and distributed in a short period of time. A recent poll has indicated that 1 in 3 people in Ireland will not take a Covid-19 vaccine. This is going to make achieving herd immunity even more difficult to achieve.
This pandemic is having a terrifying impact on physical and mental health, livelihoods and education for so many people. We are facing into a very difficult and uncertain winter. We should be in a much better place sometime next year when by then new, safe and effective, treatments and vaccines should start to become available. Mankind has survived many plagues and pestilences through the mists of time and we will beat this virus. They say that the darkest part of the night is just before the dawn.
Dr John Morgan is a native of Ballintubber, County Roscommon and is a Senior Lecturer and Principal Investigator in the School of Microbiology, UCC, with teaching and research interests in Viruses, the Immune System and molecular Genetics.