Are highland inhabitants less susceptible to COVID-19?

By Eleanor Duce

Stretching across the continent of South America at an average altitude of 4,000m above sea level, the Andean chain is the longest continental mountain range in the world, second highest outside of Asia and home to the descendent communities of the Inca Empire. Genetic adaptations that prevent Andean mountain dwellers experiencing the crippling altitude sickness from which tourists suffer appear to result in a comparatively low infection rate of indigenous peoples living at high altitudes and has led scientists to question whether COVID-19 also suffers from what is referred to in the Quechua language as ‘soroche’.

Genetic adaptations to altitude

As porters along popular trekking trails, such as those in Cusco, climb and carry incredible loads for tourists, highland inhabitants appear to have superhuman abilities to survive – and indeed, thrive – at such altitudes. Considering the demanding physical activity of life in such remote locations, scientists have long been fascinated by inhabitants’ impressive ability to withstand the harsh conditions, and studies have found that ‘differences in oxygen transport-related traits between Tibetan, Andean and European populations have been interpreted as having demonstrated the existence of genetic influences on high altitude adaptation’. [1]  Research conducted last year before the outbreak of the pandemic posited that ‘such studies can also benefit biomedical research with the identification of new therapeutic targets for treating or preventing O2 related diseases’. [2]

At altitudes above 3,000m, inhabitants survive on 25% of the oxygen concentration than the lowland average, and the ‘positive selection’ of a range of genetic cardiovascular and respiratory mutations ‘suggests greater efficiency of O2 transfer and utilisation’. Coupled with a greater total lung capacity (as physically expressed in the ‘barrel-chest’ morphology of Andean inhabitants), higher haemoglobin concentration found in Andean inhabitants’ bloodstream indicates more efficient oxygen transfer which works to mitigate the effects of hypoxia – a lack of oxygen which causes symptoms of altitude sickness in unacclimatised visitors to highland regions. The pulmonologist and former president of the American College of Chest Physicians, Clayton Cowl, explains how the pulmonary shunting which is impeded at altitude – i.e. the reduced redirection of blood flow to healthier areas of the lung to increase oxygen transfer – is also a symptom common in COVID-19 patients.

COVID-19 at altitude

A peer-reviewed study published in April 2020 in the journal Respiratory Physiology & Neurobiology, (‘Does the pathogenesis of SARS-CoV-2 virus decrease at high-altitude?’), found that populations in Bolivia, Ecuador and Tibet living above 3,000 meters (9,842 feet) reported ‘significantly lower levels of confirmed infections than their lowland counterparts.’ [3] The research attributes the phenomenon of highland inhabitants being less susceptible to COVID-19 infection to their physiological hypoxia resistance and acclimatisation to environmental factors such as higher UV levels and lower air density. In the Tibetan Himalayas, for example, where diagnosed cases were much more likely to be asymptomatic, the study observes that ‘both the pathogenesis of the SARS-CoV-2 virus and the general prevalence of infection in Tibet does not correspond to global trends.’ 

Likewise, it found that ‘the low rate of infections in Bolivia’s high-altitude population is remarkable, and clearly does not follow the often-exponential infection rates reported in many countries after an initial COVID-19 outbreak’. The stratification of infected cases in Bolivia has been particularly striking; in the high-altitude zones where inhabitants demonstrate genetic adaptation, numbers have been reported as ‘approximately three-fold lower than lowlands’. 

The study also suggests the importance of high-altitude regions as an environment which is naturally hostile to the virus. Factors such as drastic changes in temperature between night and day, air dryness, and high levels of ultraviolet (UV) light radiation (which may act as a natural sanitiser and shorten viral half-life) make the ‘survival’ of viruses like COVID-19 in high-altitudes much more difficult. Moreover, greater distance between air molecules due to low barometric pressure potentially reduces the virus’s ability to linger in the air.

COVID-19 in the Andes

Despite living in close quarters with tight knit families in multi-generational households and often with incredibly poor sanitation, indigenous Andean communities’ self-sufficient arable lifestyle, dedicated to agriculture and farming, not only maintains their strong physical health and levels of fitness but also results in infrequent contact with those from outside their communities. In a sense, it functions as a habitual social distancing, putting them at lower risk of interacting with people from the cities and urban thoroughfares. While such remote geographic locations may appear to serve as a safe haven from the virus, the isolation and social marginalisation of such communities has exposed and intensified inequalities, provoking a deep fear in many (especially indigenous women) who feel afraid and forgotten. Indeed, irrespective of any physiological and environmental ‘antidote’ to contracting the virus, the pandemic has had devastating economic and social repercussions on the wellbeing of indigenous communities. 

Travel has ground to a virtual halt around the globe, and it is hard to overestimate the impact that has, and will continue to have for years to come. Due to poor network and internet coverage, Andean communities often lack access to information and services, relying on tenuous radio signal to receive news, updates and education, and the impossibility of visiting or contacting family in other communities has left mountain dwellers feeling helpless and fearful. Moreover, dependent upon the region’s otherwise thriving tourist industry, populations are acutely vulnerable to the harsh living conditions and poverty-stricken realities of Andean living. Without the steady stream of tourists who flood to experience the magic of the sacred mountains and visit landmarks such as the Peruvian postcard destination of Machu Picchu, the remote mountain dwellers are left with little or no income. Being unable to pay for medical services (or even the transport to reach it) is another valid consideration to account for the statistics showing that Andeans are far less likely to be diagnosed with or treated for COVID-19.

Comunidad Pampa Coris

I had the privilege of being able to interview Elvia who – like many young people who migrated to pursue opportunities in the capital – moved back to be with her family in the Andes since the outbreak. Elvia was awarded a full scholarship which enabled her to study at university in Lima, and she recently began her postgraduate studies in business there. Her education has been put on hold, however, as she decided to return to the relative security of life in the community of Pampa Coris, an Andean village in the department of Huancayo, Peru. 

Situated at an altitude of 4,500m, Elvia explained to me that although the farmers had been able to sow and harvest grains as normal, restricted trade with neighbouring communities has left a significant impact on life in the village. Unable to buy or sell goods, the lack of income from the farming and agriculture, which usually sustains the community, has put a great strain on the village financially.

Elvia agrees that there could be a correlation between the cold conditions in the mountains and the survival of the virus, but she is anxious about the relaxation of the strict quarantine measures imposed throughout Peru since the first cases back in mid-March. Some departments have now lifted the total lockdown, which effectively paralysed movement both within and from the country, but did not prevent COVID-19 from running rampant in Peruvian towns and cities where poverty often necessitates an unregulated and informal economy. 

Consistent with the trend among high-altitude communities, there have thankfully been no cases in Pampa Coris nor its neighbouring villages. However, the phased freedom of movement around the country is a source of concern for the risk it may potentially pose to indigenous peoples and their vulnerable community members. Particularly mindful of protecting the village elders and children, Elvia told me that the community is cautious to prevent outsiders, and possible carriers of the virus, from entering Pampa Coris.

Indeed, as much as the virus struggles to reach such altitude-hardy communities, so do resources, commercial opportunities, internet connection, teachers, and healthcare professionals. There is strong evidence to support the hypothesis that communities living at high altitudes have a decreased risk of suffering from symptoms of COVID-19, yet it is important that our fascination with this phenomenon does not eclipse our empathy for those whose geographic isolation have intensified their social and economic marginalisation. While a myriad of medications exist on the market to combat the Western tourist’s affliction with ‘soroche’ altitude-sickness, efforts at this time must be channelled towards developing collaborative, compassionate, and sustainable remedies to support and empower indigenous communities currently experiencing the heightened challenges of life up in remote highland locations such as the Andes.

The views expressed in this article are the author’s own, and may not reflect the opinions of The St Andrews Economist.

References

[1] Lorna G. Moore.High Altitude Medicine & Biology.Jun 2001.257-279.http://doi.org/10.1089/152702901750265341

[2] Julian, Colleen G, and Lorna G Moore. “Human Genetic Adaptation to High Altitude: Evidence from the Andes.” Genes vol. 10,2 150. 15 Feb. 2019, doi:10.3390/genes10020150

[3] Arias-Reyes, Christian et al. “Does the pathogenesis of SARS-CoV-2 virus decrease at high-altitude?.” Respiratory physiology & neurobiology vol. 277 (2020): 103443. doi:10.1016/j.resp.2020.103443

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