Fighting disease

How humans have forced disease-causing microbes to adapt and evolve

Humans increase the chance new viruses will emerge in us by simply being in the right place at the right time.

Humans play host to many little passengers. Right now, you’re incubating, shedding or have already been colonised by viral, bacterial, parasitic or fungal microorganisms – perhaps all of them! Are you sick? Maybe, maybe not.

That’s partly because you have effective natural weapons and barriers that obliterate or keep your microscopic passengers contained. These immunological defences maintain a balance between us being a host and being healthy, but microorganisms are expert at confusing or escaping our cells’ defences.

Humans can live for 80 years and may produce two offspring. Compare that to the influenza virus. A virus-infected host cell can produce a thousand new particles every replication-cycle which spans hours. Viruses replicate rapidly and adapt constantly; all without any grand plan.

The replication of different viruses is affected by many factors and forces, all fine-tuned through genetic change. Random mistakes, or mutations, are thrown up during each viral replication cycle and while mostly unhelpful, sometimes they are beneficial.

A new virus with a mutation that protects it from a drug or immune defence may become the dominant (most common) virus of the thousands of newly replicated viruses in the host. These are the better adapted viruses, and are most likely to be transmitted to other people.

An electron micrograph image showing some of the ultrastructural morphology of the A/CA/4/09 swine flu virus. (Image: CDC/Wikimedia Commons)
An electron micrograph image showing some of the ultrastructural morphology of the A/CA/4/09 swine flu virus. (Image: CDC/Wikimedia Commons)

Humans increase the chance new viruses will emerge in us by simply being in the right place at the right time. We do this by travelling into once isolated forests, expanding our desire for exotic tastes and flavours, trading in live animals, through cultural practices that expose us to rare pathogens, and by incompletely or incorrectly treating infections.

How viruses adapt

For an avian influenza or “bird flu” virus to become a pandemic human threat, it needs to become better at infecting and spreading from the new human host. After a human is infected by a bird virus, the virus comes under pressure from the human’s immune response, which is hell-bent on destroying it.

Each new generation of viruses contains more of those variants that have adapted best to attach to and enter human cells.

New mutant viruses that get passed on most effectively are those that also replicate in the upper respiratory tract, because they can most easily infect new people through coughing and sneezing.

The severe acute respiratory syndrome coronavirus (SARS-CoV) is no longer detected in humans but from 2002 to 2004 it spread among us, probably having spilled over from bat-infected civet cats.

SARS-CoV gained abilities to infect and better transmit between humans and this virus caused severe human disease. But these new abilities still weren’t enough for this event to become sustained human-to-human transmission. Influenza viruses have regularly achieved such a stable place among humans.

How bacteria cope

Unlike most viral infections, for which we have no effective treatments, bacterial infections can be treated with antibiotics. But humans have grown complacent, overusing antibiotics and prescribing them to inappropriately treat viral infections or improve animal growth.

Because of us, champion bacteria have appeared that have evolved antibiotic resistance by mutating and swapping genetic elements, allowing them to avoid the effects of antibiotics and to thrive in their new environments.

The bacteria that cause tuberculosis have followed this path, as have those that cause gonorrhoea. Entire classes of once useful antibiotics are failing as more super-resistant bacteria emerge.

Parasites have evolved alongside humans and developed a balance between our body’s ability to remove them and the damage they do to us as they multiply and pass to new hosts.

The malarial parasite, Plasmodium, grows and hides in our red blood cells. Once our immune cells identify the intruder, this microorganism can suddenly change to avoid detection. Our bodies then must start work all over again to distinguish the foreign bits from our own cells.

But it’s not all bad

Not all our tiny passengers are harmful. The human microbiome comprises all the microorganisms in and on our body. Our gut microbiome includes many types of bacteria that maintain a biological balance. But when the balance is tipped, the upset has been linked to changes in sleep, mood, immunity and the development of chronic disease.

Similar balance exists on the skin, in the airways and in the reproductive tract. We can upset this balance when antibiotic treatment targeting one species of bacteria leads to increased growth of another, and may also inadvertently deplete helpful bacteria.

Many tiny passengers have evolved the abilities to grow and spread, using us as hosts. These microorganisms keep thriving because they have adapted to work around our conscious and unconscious attempts to contain or destroy them. But microorganisms can also be helpful to us in ways we’ve yet to fully understand or harness.

This article first appeared on The Conversation. This is the second article in a four-part series looking at how infectious diseases have influenced our culture and evolution, and how we, in turn, have influenced them. Read the first part here.

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“My body instantly craves chai and samosa”

German expats talk about adapting to India, and the surprising similarities between the two cultures.

The cultural similarities between Germany and India are well known, especially with regards to the language. Linguists believe that Sanskrit and German share the same Indo-Germanic heritage of languages. A quick comparison indeed holds up theory - ratha in Sanskrit (chariot) is rad in German, aksha (axle) in Sanskrit is achse in German and so on. Germans have long held a fascination for Indology and Sanskrit. While Max Müller is still admired for his translation of ancient Indian scriptures, other German intellectuals such as Goethe, Herder and Schlegel were deeply influenced by Kalidasa. His poetry is said to have informed Goethe’s plays, and inspired Schlegel to eventually introduce formal Indology in Germany. Beyond the arts and academia, Indian influences even found their way into German fast food! Indians would recognise the famous German curry powder as a modification of the Indian masala mix. It’s most popular application is the currywurst - fried sausage covered in curried ketchup.

It is no wonder then that German travellers in India find a quite a lot in common between the two cultures, even today. Some, especially those who’ve settled here, even confess to Indian culture growing on them with time. Isabelle, like most travellers, first came to India to explore the country’s rich heritage. She returned the following year as an exchange student, and a couple of years later found herself working for an Indian consultancy firm. When asked what prompted her to stay on, Isabelle said, “I love the market dynamics here, working here is so much fun. Anywhere else would seem boring compared to India.” Having cofounded a company, she eventually realised her entrepreneurial dream here and now resides in Goa with her husband.

Isabelle says there are several aspects of life in India that remind her of home. “How we interact with our everyday life is similar in both Germany and India. Separate house slippers to wear at home, the celebration of food and festivals, the importance of friendship…” She feels Germany and India share the same spirit especially in terms of festivities. “We love food and we love celebrating food. There is an entire countdown to Christmas. Every day there is some dinner or get-together,” much like how Indians excitedly countdown to Navratri or Diwali. Franziska, who was born in India to German parents, adds that both the countries exhibit the same kind of passion for their favourite sport. “In India, they support cricket like anything while in Germany it would be football.”

Having lived in India for almost a decade, Isabelle has also noticed some broad similarities in the way children are brought up in the two countries. “We have a saying in South Germany ‘Schaffe Schaffe Hausle baue’ that loosely translates to ‘work, work, work and build a house’. I found that parents here have a similar outlook…to teach their children to work hard. They feel that they’ve fulfilled their duty only once the children have moved out or gotten married. Also, my mother never let me leave the house without a big breakfast. It’s the same here.” The importance given to the care of the family is one similarity that came up again and again in conversations with all German expats.

While most people wouldn’t draw parallels between German and Indian discipline (or lack thereof), Germans married to Indians have found a way to bridge the gap. Take for example, Ilka, who thinks that the famed differences of discipline between the two cultures actually works to her marital advantage. She sees the difference as Germans being highly planning-oriented; while Indians are more flexible in their approach. Ilka and her husband balance each other out in several ways. She says, like most Germans, she too tends to get stressed when her plans don’t work out, but her husband calms her down.

Consequently, Ilka feels India is “so full of life. The social life here is more happening; people smile at you, bond over food and are much more relaxed.” Isabelle, too, can attest to Indians’ friendliness. When asked about an Indian characteristic that makes her feel most at home, she quickly answers “humour.” “Whether it’s a taxi driver or someone I’m meeting professionally, I’ve learnt that it’s easy to lighten the mood here by just cracking a few jokes. Indians love to laugh,” she adds.

Indeed, these Germans-who-never-left as just diehard Indophiles are more Indian than you’d guess at first, having even developed some classic Indian skills with time. Ilka assures us that her husband can’t bargain as well as she does, and that she can even drape a saree on her own.

Isabelle, meanwhile, feels some amount of Indianness has seeped into her because “whenever its raining, my body instantly craves chai and samosa”.

Like the long-settled German expats in India, the German airline, Lufthansa, too has incorporated some quintessential aspects of Indian culture in its service. Recognising the centuries-old cultural affinity between the two countries, Lufthansa now provides a rich experience of Indian hospitality to all flyers on board its flights to and from India. You can expect a greeting of Namaste by an all-Indian crew, Indian food, and popular Indian in-flight entertainment options. And as the video shows, India’s culture and hospitality have been internalized by Lufthansa to the extent that they are More Indian Than You Think. To experience Lufthansa’s hospitality on your next trip abroad, click here.

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This article was produced by the Scroll marketing team on behalf of Lufthansa as part of their More Indian Than You Think initiative and not by the Scroll editorial team.