VIRUSES – OUR FRENEMIES?
Mr Joseph Mani who has mastered the art of writing articles based on logic and scientific temper, explains viruses and their `lock and key' relationship with a host, for the understanding of us laypersons. He says while some viruses are our friends, many others are our enemies. For this he has coined the word `Frenemies'. He says some viral infections grow exponentially as Covid-19 has done with 26.1 million persons infected and 864,000 deaths worldwide as on today. The reasons for the spread of viruses and pandemics are humans encroaching on the natural habitats of wild animals, treating them in unnatural ways (wet markets), travel & interconnectedness, and overcrowding due to population explosion.
He ends with an optimistic note that advances in science & technology and communication will give us unprecedented capacity to catch future outbreaks early and stop them. Isaac Gomes, Associate Editor, Church Citizens' Voice.
All the experts (and non-experts) tell us that the Coronavirus is here to stay and we better learn to live with them. If that is so it may be worthwhile to get some understanding of these uninvited guests who will be taking up permanent residence within us.
What are Viruses?
A virus is a type of microbe. Other types of microbes are bacteria, fungi, algae and protozoa. A bacterium is a single cell; it is a living thing in the sense that it can survive and reproduce by itself. A virus can be said to be a ‘dormant’ living thing in that it cannot survive and reproduce by itself; it becomes a living thing only when it attaches itself to another living cell. Bactria can be filtered out, viruses are too small to be filtered; bacteria can be reproduced in a petri dish in the lab, a virus in its original form cannot be; if a bacterium causes disease it can be treated with antibiotics, viral diseases usually cannot be cured with antibiotics.
How small are viruses? A bacterium is about 0.4 micron while a virus is about 0.02 micron (One micron is one millionth of a meter). If the human body is blown up to the size of a football field a bacterium will be as small as the football and a virus will be about 1/20th of a bacterium. A bacterium is a giant compared to a virus.
Microbes and Viruses are Ubiquitous
The chair we are sitting on, the computer screen where we are reading this article, the coffee cup and the coffee we are sipping and our body inside and outside are seething with tiny creatures. This alien army of microbes occupies every surface, insect, plant, animal and human on earth. The bravest soldiers of this army are the smallest. These are the viruses.
Microbes have a larger biomass than all the insects, plants, animals and humans put together. If we make an encyclopedia of life forms based on diversity and biomass, the majority of the volumes would be on these unseen beings, one very slim volume would be on the seen world of insects, plants and animals. Humans would get a footnote – in bold type, but only a footnote.
Microbes have been in existence for about 3.5 billion years. They are by far the most abundant form of life on earth. There are about 5 x 1030 bacteria on earth and viruses are 10 times more. For example, there are about 250 million virus particles in one millimeter of sea water. Viruses are also staggeringly diverse – there are about 100 million different types of viruses. The more than a trillion entities in the universe, though huge, were invisible to us because they are too far away. In 1616 Galileo with his telescope made them visible. Microbes were invisible because, though very close, they are too small to see until in 1666 the Dutch les-maker Antonie van Leeuwenhoek with his microscope made us realize that there are trillions of tiny creatures around and inside us.
How Viruses Attach Themselves to Human Cells
A virus consists of two basic components: their genetic material, either DNA or RNA, and a protein coating that protect its genes. The outer coating determines the shape of the virus and identifies the virus family it belongs to and the kind of disease it causes: pox viruses are brick-shaped, herpes 20-sided sphere (like a football), rabies bullet-shaped, tobacco virus is long and thin like a rod, coronaviruses are crown-shaped.
There is a “key-and-lock” system by which a virus attaches itself to a living cell. Its protein coat has a “key”. When it finds a cell which has a “lock” where its “key” fits, it attaches itself to that cell. The virus then hijacks the machinery of that cell to survive and propagate. The key of each virus can open only the lock of a specific kind of cell, so different viruses attack cells of different parts of the body and cause different diseases– liver, nerves, respiratory lining, gut.
Many Microbes and viruses Are Useful
Not all viruses are harmful. Some are neutral living peacefully with the host organism. Some viruses play a useful role in keeping the ecosystem balanced. Microbes on the surface of the sea use sunlight for photosynthesis and release oxygen; half of the world’s oxygen is produced this way. Unfortunately microbes at the bottom of the sea produce 650 million tons of carbon dioxide per annum, compared to the 21.3 million tones produced by humans burning fossil fuels.
The plant food we consume requires enzymes for digestion. Enzymes produced by our body is not enough. It is supplemented by enzymes produced by the abundance of a particular microbe in our guts. Obesity is caused when there is not enough of this bacterium.
Vaccines are viruses. The smallpox vaccine is a live virus, others like oral polio vaccine and MMR are viruses we have created in the lab, the influenza vaccine is a virus we have made incapable of reproducing themselves but can activate an immune response, vaccine for hepatitis B uses selected parts of the actual virus. All vaccines in some way use viruses to fight infectious diseases. The word vaccine itself is derived from Latin meaning cowpox.
Then there is virotherapy. One virus from the piconavirus family causes polio; another virus from the same family is found to be able to kill certain type of cancerous cells, but does no harm to healthy cells. Researchers are also working on adapting the herpes virus, the common cold virus and the measles virus to cure cancer. Another virus found in a high percentage of people does no harm to us, but can prolong the lives of AIDS patients.
A harmless virus can become harmful by mutation or combining with another virus. Mutation is a mis-reading of the genetic code. When a gene mutates the DNA corrects it. Even then a few mutations go undetected and get passed on to the next generation, for better or for worse. This is how evolution works. Some viruses like the flu virus mutate rapidly; this year’s effective vaccine will be ineffective next year. So we need a new vaccine every year, but to find a vaccine we have to know what form the new mutation has taken which we will know only after infections have started; then it takes at least six months for the new vaccine to be ready by which time the infection would have become an epidemic. The “common cold” viruses are of so many different types that our immune system cannot cope with them. The coronavirus is a retrovirus meaning it works with RNA and not with DNA. RNA has no self-correcting mechanism, so all mutations get passed on to next generation of viruses. Some like the Covid-19 virus mutate slowly and hence its different avtars are not very different from each other; the same vaccine will be effective for most of them, at least that is the present hope.
Microbes and viruses are part of our heritage, we inherited them from our pre-animal and animal ancestors. Viruses from animals jumped to humans starting with our hunter-gatherer ancestors for whom hunting was subsistence not entertainment. About 60 per cent of known infectious diseases in humans have come from animals. Examples are: henta and lasa viruses jump from rodents to humans, yellow fever and herpes from monkeys, monkeypox, despite its name, is from squirrels, influenza from wild birds to domestic poultry, sometimes with a stopover in pigs, measles from cows, sheep and goats, HIV from chimpanzees, dengue and chikungunya (the word is from the Bantu language) are from primates, and zika from rheus monkeys – all three are spread through mosquitoes. But bats are hosts for the maximum number of scary viruses: Hendra, SARS-CoV, rabies, ebola, nipah, to mention just a few. Left in their natural surroundings they are mostly harmless. But as these animals are domesticated, herded together and housed in containers and cages in close proximity, viruses get exchanged, they form new combinations creating emerging viruses which can be deadly for humans and against which we have no immune defense because we had never encountered them before. As we move animals quickly and efficiently around the globe viruses in these animals spread all over the world. In the 1930s the cytrid virus infected frogs in South Africa, causing the extinction of some frog species. This remained confined to Africa. Then a lab technician injected the urine of a pregnant woman into a frog and the frog ovulated. This became a useful though cumbersome pregnancy test. Thousands of frogs were exported from Africa to other continents to be used in pregnancy tests. They took the cytrid virus with them.
Normally pets do not carry harmful viruses, but they can get a new virus if they come in contact with wild creatures, for example bats. People who are in close contact with animals are susceptible to infections. Some Hindu and Buddhist temples have monkeys around them. Pilgrims and tourists often touch these monkeys, either because of belief or curiosity (some people believe that if a monkey eats from their hand their prayer is guaranteed to be heard). These people then take home not only photos and memories but also a virus called Simian Foamy Virus which affects monkeys and humans and the virus reaches far off places. These monkeys also carry Herpes B virus, but this virus does not jump from monkeys to humans.
Today with air travel, a person or animal can carry a deadly virus to places thousands of kilometers away in a few hours. This means even viruses that have a short life can spread far and wide. Where it spreads to depends not so much on how far the place is as how connected the place is. See how SARS went global: A fishmonger called Zhou Zuofeng from the Guandagong province in China got infected with the SARS virus probably from a wet market. He gave the infection to 72 people including 58 healthcare workers in two hospitals. One of those infected in the first hospital was a professor of nephrology called Liu Jianlum. He and his wife travelled to Hong Kong to attend his nephew’s marriage. They stayed in the popular Metroplole Hotel. A 78-year old grandmother from Toronto and a young woman from Singapore also stayed at the Metropole at the same time. The Registrar of the hospital where the young woman was treated travelled to New York via Frankfurt to attend an infectious-diseases conference. So the virus travelled from Hong Kong to Canada, Singapore and Germany and WHO issued a global alert about Severe Acute Respiratory Syndrome.
Sports events can carry a virus from one continent to another as happened the way the Zika infection reached Latin America from French Polynesia during a football cup. Infections increase during school days and decline during school holidays.
Blood transfusion, organ donation, injections, surgeries and the dentist’ drill save lives. They can also carry infections from one person to another. Sneezing, kissing and sex are other ways infections spread. Eating eggs is considered good for health. But eating eggs away from home may cause disease because some chickens are infected with harmful bacteria. Use of antibiotics can kill useful microbes which act as a shield against harmful bugs in our stomach leading to disease. A virus cannot enter our body through the multiple layers of our skin, but a microscopic abrasion of the skin allows it to enter inside.
Most infections grow exponentially. So bringing down new cases through quarantine and lockdown can make a huge difference specially if it is done initially. But segregation and stigma make people reluctant to report cases which make it difficult to control the outbreak. Naming and blaming is not new. In the 16th century the English believed that syphilis came from France, the French said it came from Naples, Russians called it the Polish disease, Poland said it came from Turkey and the Turks blamed the Christians for it. Countries also hide cases. The 1918 Flu pandemic originally came from China and spread to many countries. At that time England, Germany and France had war-time censorship which blacked out news of the epidemic in their countries for the sake of morale. Spain had no censorship and reported cases, so it appeared that Spain alone had the flu and it was named Spanish Flu. CoVid-19 is not the only instance where China initially blacked out the news; they did the same thing about SARS. Not all epidemics started in China. HIV originated in Africa, Q fever in Australia, Cholera in India.
Whether an infection will become a pandemic can be predicted to some extent and there are organizations devoted to such studies. There are two caveats about such predictions: Predictions through mathematical models are based on past data and a new virus may refuse to behave like its predecessors; second, if a pandemic is predicted and public health authorities take timely action, the infection is arrested and there will be no pandemic. There is no pandemic precisely because it was predicted, a case of reverse self-fulfilling prophecy.
A lion kills and eats an antelope not because it has an inherent hatred of antelopes but for it to survive. We eat plants not because we hate plants but because we need food to survive. When a virus infects a human or animal, it is not doing it to harm the host; it is doing what evolution has wired it to do. It is doing it to survive since it cannot survive and propagate by itself.
Harmful viruses are a minority; the majority are harmless, others are very useful and necessary. So living in a completely sterile world is asking for trouble. Our aim should be to identify which are the rogue ones and which are useful, neutralize the former and cultivate the latter.
Humans encroaching on the natural habitats of wild animals, treating them in unnatural ways, travel and interconnectedness combined with overcrowding due to population explosion facilitate spread of viruses and cause of pandemics. At the same time advances in technology and communication give us unprecedented capacity to catch outbreaks early and stop them. Will pandemics inevitably sweep through the human population periodically, killing millions or will science and technology march in and rescue us? If history is any guide, optimism about the future is warranted.