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Zoonotic Infectious Diseases: Local Origins, Global consequences

Engage! – Discussions on active involvement in personal health and global wellness

On December 31, 2019, twenty-seven cases of pneumonia of unknown origin were reported in Wuhan, China. By the second week of January 2020, the first case outside China was reported in Thailand. On January 30, 2020, the WHO declared an international public health emergency. Since those events transpired none of us have escaped the effects of the waxing and waning of SARS-CoV-2 as it has raged around the world over the past 18 months. 

If there is a positive fallout from this event, it is the explosion of international scientific efforts to find a way to control this deadly virus. The first sequence of this coronavirus was publicly available in January 2020, and vaccines were created within the next six months, both achievements as epic as the urgency created by this unprecedented (at least in our lifetime) international crisis. Simultaneously, the origin of this virus is being investigated, and expanding upon the knowledge that bats are the natural host of previous coronaviruses that caused human epidemics, namely SARS-CoV and MERS-CoV, it appears that SARS-CoV-2 managed to jump to humans from bats. In order for the jump to human infectability to occur, mutations occurring in the virus genome create a viral surface protein that can bind specifically to a human cell surface protein; in the case of SARS-CoV-2, this could be a mutation that allows the viral Spike protein to bind the human cell surface ACE2 protein and cause infection. 

COVID-19 structure
COVID-19 structure

This process of zoonosis, involving the adaptation and transmission of infectious agents from a primary host that is either a mammal or a bird to humans, is an evident aspect of over a hundred infectious diseases known to afflict humans. The infectious agent involved could be bacteria, fungi, parasites, or viruses and in addition to known diseases, there is a continuous roster of emerging zoonotic diseases as these opportunistic microorganisms try to find new hosts to live and breed in. Transmission from animal to human may be through direct contact through potential scratches or bites, airborne through droplets for instance, through vectors such as mosquitoes, ticks, and lice, ingestion of contaminated food or water, and by contact with infected vegetation, soil, water, wild animals, etc. Transmission of pathogens across oceans and borders after they have adapted to humans can, unfortunately, become a reality with the ease of international travel, especially if they can achieve efficient human-to-human transmission and become highly infectious, as in the case with SARS-CoV-2. 

Commonly known extant zoonotic diseases include rabies, plague, chagas disease, brucellosis, anthrax, bovine tuberculosis, Japanese encephalitis, zika virus, ebola, and AIDS. All these, and many more, are of direct relevance to India and other tropical and sub-tropical countries including south-east Asia, Africa, South America, western Pacific islands, and parts of Australia where they can be a burden on the public health system and economy. In India, 13 zoonoses are associated with 2.4 billion cases of human disease, and 2.2 million deaths per year. The National Center for Disease Control in India coordinates efforts at early diagnosis and effective containment, and a specific focus is in the handling of animals and regulation of human-animal contact. Peri-urban areas have grown rapidly in India, and are a link between agricultural areas and densely populated sites. They present a risk as there is unregulated livestock-based food production in these areas to meet the increased demand for food products. 

In addition to these existing illnesses, it is estimated that 60-80% of emerging infectious diseases are zoonotic diseases. Change in land use is thought to be a major underlying cause of this especially in Southeast Asia and in tropical and developing countries, coupled with wildlife diversity. Depending on the use that the deforested land is co-opted for, be it monoculture forests, crops. poultry, livestock. housing, etc., different groups of zoonotic species came to the fore. For instance, strong associations of vector-borne diseases were found with monoculture plantations (for instance, rubber), and bacterial and viral diseases are among others associated with livestock farming. In India, which is one of the hot spots for emerging zoonotic diseases, potential reasons for the emerging disease include changing land use, dairy farming, rodent infestations, wild-animal trading, climate change, and improper farming practices. Coupled with these conditions there is a lack of awareness, poverty, and poor access to medical and diagnostics services. Endemics, epidemics, and emerging zoonotic diseases in Australia have been a constant presence between livestock, horses, and humans. These are mostly viral and vector-borne diseases, and a few examples are Nipah virus, Menengle virus, and JE virus

Examples of zoonotic diseases and their affected populations.
Examples of zoonotic diseases and their affected populations.

Triggered by the ongoing SARS-CoV-2 pandemic, the World Wildlife Fund has published a report on the zoonotic disease risk posed by wildlife markets in southeast Asia that are involved in wildlife trade and consumption. They urge governments to impose regulations on these activities and reduce demand for high-risk wildlife products. Other comprehensive and phased efforts to prevent and control known and new pathogens have been reported from Congo (monkeypox virus), Ethiopia (rabies), and Georgia (a new zoonotic virus). Of particular concern to India is the potential for it to become a hotspot for future variants of SARS-CoV-2, with global consequences. With its density of population, a priority is to exercise COVID19-related behaviors of masking, social distancing, and vaccination. A second priority is sequencing variants as they arise and following them epidemiologically with outbreaks of COVID19. 

In urban settings, most contact with animals is relegated to pets, household pests, and the consumption of meat and dairy products. Obviously, food needs to be handled with care and cooked well, and pests ranging from rats to mosquitoes and flies need to be eradicated. Although specific viruses can infect dogs and cats, there is currently no evidence that these transmit to humans and cause disease. However, there is some evidence that pets can test positive for SARS-CoV-2, with infection transferring from infected humans. Import and close continuous contact with exotic and wild animals as pets is not recommended. 


L. Iyengar has lived and worked in India and the USA. A scientist by training, she enjoys experiencing diverse cultures and ideas, and writing. Her short story will be included in an anthology showcasing a group of international women writers, to be published in 2021 by The Nasiona. She can be found on Twitter at @l_iyengar and www.liyengar.com.


 

Bacterial strains in the guts of humans and chimpanzees diverged and began to evolve separately 5 million years ago and 15 million years ago in humans and gorillas. Humans and apes evolved into a new specie at about the same time. A mutually beneficial relationship between gut bacteria and animal hosts may contribute to the formation of a new species (Credit: Darryl Leja, National Human Genome Research Institute, National Institutes of Health)

A Microbe Connection: the Good, the Bad, & the Necessary

Engage – Discussions on active involvement in personal health and global wellness.

This two-part series highlights the emerging relevance of our microbiome in human health. In this first part, we discuss the establishment of the microbiome from infancy to adulthood and the highly responsive nature of these trillions of cells to the environment. The geographical diversity of microbiomes in various cultures, and the mandatory nature of the acquired living situations of immigrants are of immediate relevance. The second part, which will be published in June, will focus on the effects of the microbiome on human health and disease. 

Traditionally, our interaction with microbes has been focused on how deleterious they can be. Viruses, bacteria, and other microorganisms have been responsible for several contagious diseases, including typhoid, cholera, mumps, smallpox, polio, malaria to name a few, some of which we take credit for controlling with medicines and vaccines. 

However, emerging knowledge of the human microbiome is informing us that an entire army of microbes including bacteria, fungi, viruses, and other fauna coexist in symbiotic (meaning mutually beneficial) and commensal (meaning neutral coexistence) relationships with our bodies, and are beneficial in that they play an important role in maintaining homeostasis and optimal functioning of the body. Comprising of at least an equal number of cells as the human body itself, the microbiome constitutes what is termed a newly discovered organ in our bodies – one that is dynamic, diffuse, and very different from what we conventionally think of as a discrete human organ (liver, heart, brain or lung). 

Microbiota colonize the entire surface of our bodies and the specific niches within. Several studies have tried to describe the species that are found in various locations, and these descriptive studies paved the way to deeper ones aimed at understanding how they are established, maintained, and function. We are learning that the establishment of these populations occurs from the earliest days of one’s existence, and their effective maintenance throughout one’s life is as important as having a healthy heart. 

Infants are exposed to the maternal microbiome during the process of birth, and differences in the complexity of their microbiomes are seen in normal birthing situations versus cesarean sections. During their early days out of the womb, colonization of microbes within their bodies and also on their skin is associated with good overall health, in the immediate and long term. Taken a step further, this intergenerational transmission can be extended to envision a co-evolution of humans with their microbiomes as a discrete ecological unit. Members of a family, or people who occupy the same household, are known to share similarities in their associated microbiomes. A linear study of 6 large Indian joint families also indicated changes in microbiome with age.

Further afield, one can well imagine that geographical and cultural differences will lead to variations in associated microbiomes. Most of us are aware that microbes exist in the intestines and mouth, and there is an immediate and important influence of diet on these populations. While different species of bacteria have been found to be the dominant population in different geographies, one study reported that the African diet was associated with the most gut microbial diversity. In general, a lack of microbial diversity is associated with urbanization and developed countries, and some factors thought to be related to this outcome are increased consumption of processed foods, increased use of antibiotics, reduced sleep, and loss of natural habitat. This lack of microbiome diversity is directly related to human disease. We are learning that diet can lead to changes in the microbiome in a matter of hours, not days, and can regulate the secretions of the bacteria in addition to the populations of the bacteria themselves. 

South Asian diet contributing to gut microbiomes.
South Asian diet contributing to gut microbiomes.

Even within the same geography, different lifestyles and ethnic groups showed differing gut microbiomes. In a cross-sectional study in Malaysia, the gut microbiome of Malaysians of Malay, Chinese, Indian and Jakan descent varied principally by ethnicity of the subjects, who were of the same socioeconomic status and geographic location. Perhaps more relevant to this discussion, studies conducted to compare gut microbiomes in rural and urban groups in Thailand and India suggested that urban populations have reduced numbers of bacteria that can produce beneficial anti-inflammatory molecules. In most cases, researchers associate these reductions and changes in gut microbial diversity with dietary preferences of urban and rural settings- urbanites tending to include less natural foods, vegetables, and whole-grain in their diets. 

Pioneering studies in immigrant communities were conducted in Amsterdam and Minnesota. The Amsterdam study analyzed six immigrant ethnic groups including Moroccan, Turkish, and South Asian Surinamese, and as with the Malaysian (non-immigrant) study the gut microbiome varied principally by ethnicity. Southeast Asian immigrants from Laos, Vietnam, Myanmar, and Thailand were sampled in Minnesota, and it appeared that their gut microbiome assimilated to their new homeland. It took about a decade for this group to substantially transition to the US-associated gut bacterial profile. Although diet would play a big role in this, it is thought that other lifestyle changes, medicines including antibiotics, and other as yet unexplored variables may play a role in this remarkable change. An unfortunate correlation among these immigrant populations is the onset of obesity and diabetes. 

Our understanding of this complex and dynamic organ continues to develop, in tandem with our understanding of its involvement in human health. These aspects will be discussed further in the second installment of this article. 


L. Iyengar has lived and worked in India and the USA. A scientist by training, she enjoys experiencing diverse cultures and ideas and writing. Her short story will be included in an anthology showcasing a group of international women writers, to be published in 2021 by The Nasiona. She can be found on Twitter at @l_iyengar. www.liyengar.com

Featured image license here.


 

Two Fallouts of Working Behind a Screen

I have been working from home since the middle of 2020, ever since the pandemic struck. There are two fallouts that I have experienced from that.

One was unexpected.

My finger rings had been acquired over the years and were designed to fit well either on the fingers of my left or right hand. All my life, up until this point, the fingers of my right hand were thicker than the respective fingers of my left hand, which made perfect sense as my right hand is the dominant one. Now, to my surprise, I was able to wear rings on my right hand that refused to slide beyond the knuckle of my left hand.

Curious! After some due consideration, I attributed it to the increased computer workload and typing. My style of typing involves a greater reliance on my left-hand and these fingers get a good workout. On the other hand (no pun intended), my right-hand moves around, maneuvers the mouse, hits delete, space, and other non-word keys – a moderate all-around workout. I consider the ring conundrum solved. 

The second fallout was less amusing. My eyes started reminding me, in no uncertain terms, that something was different and I needed to pay attention. Severe eye strain coupled with headaches occurred with increasing regularity, becoming altogether too frequent, compromising work, recreation, and life itself.

I made an appointment with my local eye-care provider as my eyes clamored for attention. My optometrist handed me a card with printed material of various sizes on it and asked me to read it. As I read the card, I couldn’t help but smile. Apparently, I learned as I read, Galileo had affirmed in his 17th-century analysis of the senses that sight was the ’most excellent and noble of the senses.’ Neither Galileo nor my optometrist was going to get any argument from me on that point. 

Working from home definitely has its perks. It saves the environment from fossil fuel exhaust, deletes the interminable boredom of getting stuck on the freeway, and drastically reduces the infections one tracks back home from work. However, it also allows one to get sucked into a routine of being wedded to the computer for endless stretches of time. Ironically, even what counts as relaxation- reading the news, or playing a game- is channeled through a screen. This lifestyle leads to an escalating increase in screen time.

Working in an office environment involves movement that we take for granted. We attend face-to-face meetings seated around a table, converse with colleagues and friends, walk to the cafeteria or a seminar, and commute to work. Setting up an office at home inherently gives priority to a quiet space within the home environment, where the computer screen is the focal point. In the present pandemic, meetings, conferences, seminars, even happy hours are conducted through the screen, not to mention the actual work. Several of us are sucked in this routine for at least five days a week, and those windows to our soul need our conscious protection. 

An eye.

This dependence on digital technology has led to a condition that has been dubbed digital eye strain (DES). The most obvious symptom is headache, especially around the back of the eyes. Other indicators include strained eye muscles, neck and shoulder pain, irritated eyes and blurred vision, light sensitivity, along with an increasing dependence on prescription eyeglasses.

Eye strain is a result of continuously forcing the eyes to focus on a relatively close and bright screen. Constant focus on an object that is at a close distance strains the eye muscles. Secondly, uninterrupted focus on a bright object also causes strain.

A simple fix to the distance issue is to use what is commonly called the 20-20-20 rule. Focus your eyes on a distant object about 20 feet away, for 20 seconds, at 20-minute intervals. Focusing on a distant object relaxes the eye muscles, and it takes 20 seconds for the muscles to relax. Next, maintain the brightness of the screen at approximately the level of the ambient light. Although there is mention that the blue light wavelengths emanating from screens damage the retina, a sensitive nervous layer at the back of the eyes, there is not enough evidence to confirm this. Nevertheless, protecting the eyes with lenses designed for computer work is not a bad idea. Also keeping the monitor about 1.5 to 2 feet away from your face will help mitigate both these contributing factors. 

Moderation is the key. It is important to take frequent breaks away from the workstation, stay hydrated, use artificial tears if the eyes feel dry, and find a comfortable posture and office desk/chair set up to enable less strain on the body while your mind is working at warp speed. 

Your eyes need to last you for your lifetime. Providing them with the best framework to keep up their essential work, and cope with the prevalent times, seems prudent at the very least. 


L. Iyengar has lived and worked in India and the USA. A scientist by training, she enjoys experiencing diverse cultures, ideas, and writing. Her short story will be included in an anthology showcasing a group of international women writers, to be published in 2021 by The Nasiona. She can be found on Twitter at @l_iyengar.