The COVID-19 pandemic in the Tibet Autonomous Region: A single-center review

To the editor,

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, that is coronavirus disease 2019 (COVID-19), has resulted in millions of deaths worldwide since December 2019.¹ Before August 2022, there were relatively few cases of COVID-19 in the Tibetan Autonomous Region in China, which may be associated with high-altitude hypoxia, exposure to ultraviolet light (UV), and low atmospheric pressure.² However, an outbreak of the SARS-CoV-2 omicron sub-variant BA.2.76 throughout the Tibetan Autonomous Region after July 2022 contradicts the notion that Tibet has been exempt from COVID-19 for the past 3 years.

In fact, due to constant evolution and spread through asymptomatic carriers, the virus is also highly infectious in high-altitude regions with strong UV and low atmospheric pressure, in contrast to previous reports. Previous studies have reported that SARS-CoV-2 infection and COVID-19-related mortality rates are lower in populations residing in high-altitude, as compared to low-altitude regions.³

In the present study, in total, 3465 individuals (1690 inpatients and 1775 caregivers) were admitted to our hospital from August 1, 2022 to October 31, 2022. The positive COVID-19 of the nucleic acid test results was observed in 75.5% (194/257) adults (age, ≥15 years), and 24.5% (63/257) were children (aged, ≤14 years), which included 40.5% (104/257) males and 59.5% (153/257) females. The SARS-CoV-2 infection rate of females was highly, which may be related to predominance of females in the overall population (2421/3465). However, it is unknown whether females are at a greater risk for infection with the SARS-CoV-2 variants. All of inpatients and caregivers, rates of 87.9% (3047/3465) were Tibetan and 12.1% (418/3465) were Han population. In the positive cohort, 85.2% (219/257) for the overall SARS-CoV-2-positive Tibetan population.

In accordance with the clinical guidelines for COVID-19 Diagnosis and Treatment published by the National Health Commission of China (9th edition), the rates of cases with mild, moderate, and severe symptoms were 48.3% (124/257), 41.2% (106/257), and 10.5% (27/257), respectively. Last three months, of the 1600 employees in our center, approximately 112 (7.0%) developed SAR-CoV-2 infections, 9 were classified as severe, timely appropriate measures are particularly important to prevent infection of healthcare workers.

All of 257 positive COVID-19, there were no deaths, indicating relatively low pathogenicity in Tibet, which is likely related to the genetic background of populations residing in high-altitude regions, such as low expression of angiotensin-converting enzyme 2 receptors, which lowers susceptibility to SARS-CoV-2 infection.⁴ In addition, tolerance to long-term hypoxia of populations residing in high-altitude environments leads to increased molecular levels of hypoxia-inducible factor 1α and 2α, which trigger adaptive responses to hypoxic conditions and attenuation of acute respiratory illnesses,⁵ this theory provides some evidence for SARS-CoV-2 infection at high altitudes is rarely associated with severe symptoms. However, we speculate that transmission related to viral mutation is also a key factor, thereby presenting new challenges to control efforts.

Mutant variants of SARS-CoV-2 can adapt to harsh conditions at high altitudes and spread among local populations, suggesting that infection prevention and control efforts should be continued in some regions to protect public health.

Funding sources

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

None declared.