Today’s news is littered with reports of Monkeypox, long Covid, variants BA.4 and BA.5 and their skill at evading previous immunity, and rising rates of reinfection. And the serious and death rates keep rising. But this isn’t new news.
- In 1346-53 the Black Death caused an estimated death of 25 million people across the world in the 14th century. According to scientists, the outbreak was caused by a bacteria called Yersinia pestis. This Bubonic Plague lasted for about four years.
- Flu pandemics in 1889-90,
- Spanish flu 1918-20,
- Asian flu 1957-58,
- AIDS in 1981,
- Ebola, SARS
- and on they go
Covid and Plague similarities
The Bubonic plague, wiping out 25 million people and Covid with 6.5 million deaths are both deadly epidemics. Both evolved from the East, spread among the population in cities and towns, and made its way to different countries through international trade. There is mounting evidence that an Ebola-like virus was the actual cause of the Black Death and not spread by flea-ridden rats.
Safeguards for Covid include face masks and full protection suits or PPE. For the Black death the European ‘plague doctor’ ( Medico della Peste), wore a long cloak and grotesque bird-like mask. The eccentric headpiece served as a kind of primitive ‘gas mask’ for medical practitioners in 17th-century Europe, designed to protect its wearer from the foul odours associated with the plague.
The plague doctors primary responsibilities were more administrative and laborious to tally and keep track of casualties, assisting in the occasional autopsy, or witnessing wills for the dead and dying. By the time of the 17th-century though, physicians had subscribed to miasma theory, which was the idea that contagion spread through foul-smelling air. Prior to this time, plague doctors wore a variety of protective suits but it wasn’t until 1619 that a “uniform” was invented by Charles de l’Orme, the chief physician to Louis XIII. This uniform consisted of a waxed leather coat, leggings, boots, and gloves intended to deflect miasmas from head to toe. The suit was then coated in suet, hard white animal fat, to repel bodily fluids. The plague doctor also donned a prominent black hat to indicate that they were, in fact, a doctor.
The full PPE for today’s medical staff consists of a tight fitting surgical face mask, articulate filter respirators (such as P2 or N95), gloves, goggles, glasses, face shields, gowns and aprons.
We live in a world of viruses that are unfathomably diverse, immeasurably abundant. The oceans alone may contain more viral particles than stars in the observable universe. Mammals may carry at least 320,000 different species of viruses. About 60% of infectious diseases can be attributed to viruses, bacteria and pathogens. Viruses evolve fast. Exceptionally fast. Faster than any other organism on Earth—and the new coronavirus is no exception.
As long as there are vulnerable populations that can be infected, the virus will transmit, replicate, and mutate, evolving as it spreads. Evolution by natural selection is a law of biology in the same way that gravity is a law of physics; it is a literal force of nature. Continued spread of this virus will lead to further mutation, new variants, more deaths, and an ongoing pandemic.
The human body contains a plethora of microscopic bugs – bacteria, Protozoa, fungi etc. Very few cause disease, and the majority exist in a symbiotic relationship. Some devour dead skin, others help to break down indigestible molecules, whilst our bodies provide food and shelter.
Bacteria v Viruses
Bacteria are the direct descendants of earliest life on earth and are the smallest microbes which can survive without help from any other living thing. A virus is up to 500 times smaller than bacteria. The word ‘virus’ means a submicroscopic entity.
Viruses on the other hand cannot ‘graze’ on us. They have to penetrate our living cells in order to survive. They are parasites, taking what they need and giving mouthing in return. They are clever, subversive, subtle and ingenious. They appear to plan an attack and survival strategy, but have no brain.
Once a virus is in a host it has but a short time to invade a cell and establish an infection. War is declared between the host’s immune system and the virus.
As a virus replicates, its genes undergo random “copying errors” (i.e. genetic mutations). Over time, these genetic copying errors can, among other changes to the virus, lead to alterations in the virus’s surface proteins or antigens. Our immune system uses these antigens to recognise and fight the virus. This change of mutations in the surface proteins of the virus is antigenic.
- “Antigenic drift” where the surface proteins trigger immune responses in the host. The small changes that occur from this antigenic drift usually produce closely related viruses with similar properties. However, the small changes associated with antigenic drift can accumulate over time and result in viruses that are antigenically different such that a person’s existing antibodies won’t recognize and neutralize the newer viruses.
- Another type of change is called “antigenic shift.” Shift is an abrupt, major change that can result in a new subtype – a new novel virus. Fortunately these Shifts happen less frequently. When a virus undergoes both antigenic drift and shift then this can give rise to a pandemic.
How did viruses evolve?
Were they rogue pieces of genetic material that have broken free from chromosomes and reproduce independently. ‘Jumping genes’ free themselves from the DNA chain of a chromosome and rejoin at another site but are trapped within a cell. The answer is not clear and scientists are still investigating.
Scientists studying the ‘flu virus and how it changes to escape natural or vaccine-elicited immunity, have a clearer understanding of viruses. That’s why they constantly update influenza vaccines as they change in the two main ways, antigenic drift and antigenic shift.
However without viruses humans wouldn’t have evolved. There are two lengths of DNA that originated from viruses and now reside in the genomes of humans and other primates, for instance, without which—an astonishing fact—pregnancy would be impossible.
Although viruses are parasites, sometimes that parasitism is more like symbiosis, mutual dependence that profits both visitor and host. Viruses are easier to describe than to define. Each viral particle consists of a stretch of genetic instructions (written either in DNA or that other information-bearing molecule, RNA) packaged inside a protein capsule (known as a capsid). The capsid, in some cases, is surrounded by a membranous envelope (like the caramel on a caramel apple), which protects it and helps it catch hold of a cell. A virus can copy itself only by entering a cell and commandeering the 3D-printing machinery that turns genetic information into proteins. If the host cell is unlucky, many new viral particles are manufactured, they come busting out, and the cell is left as wreckage. However if the host cell is lucky, the virus could simply settle back by going dormant or back-engineering its genome into the hosts.
How viruses originated or how they are able to mutate and survive is still keeping scientists busy.