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Published Online: 21 December 2020

Letter to the Editor: COVID-19 Infections Do Not Change with Increasing Altitudes from 1,000 to 4,700 m

Publication: High Altitude Medicine & Biology
Volume 21, Issue Number 4
Dear Editor,
Coronavirus disease (COVID-19) infection, after the first case reported in Wuhan, China, on December 31, 2019 and declared a pandemic by the World Health Organization in March 2020, has climbed by September 2nd to 26,076,572 cases and 864,162 deaths worldwide.
Although it has been suggested that living at high altitude could decrease the rate of coronavirus transmission and mortality from COVID-19 (Arias-Reyes et al., 2020), new studies have not confirmed this protective effect. In fact, the case–fatality rate in Peru did not change with altitude (Segovia-Juarez et al., 2020).
In the United States and Mexico, populations located >2,000 m have a higher total cumulative number of COVID-19 cases and a higher mortality rate attributable to COVID-19 than those located <1,500 m (Woolcott and Bergman, 2020). This study included data up to April 13, 2020, in the United States and up to May 13, 2020, in Mexico.
A recent comprehensive review calls into question whether environmental factors, particularly ambient hypoxia, may be responsible at high altitude for reducing viral transmission and mortality due to COVID-19 (Pun et al., 2020). These conflicting results need further clarification and more current data. For this, we have assessed data from Peru, a country with one of the highest per capita number of infections and mortality rate worldwide.
We used data of COVID-19 cases from 1,636 districts located from 5 to 4,705 m. The data set of COVID-19 cases (N = 535,946, from March 6 to August 15, 2020) was obtained from the National Open Data Platform (MINSA, 2020). Population and altitude data were gathered from National Institute of Information and Statistics (INEI, 2019), and combined with the aforementioned data set. This afforded altitude and district population information for 509,521 positive cases, representing people living at different altitudes, and providing the possibility of studying the effect of altitude with enough power to determine statistical significance.
We considered three ranges: (1) altitudes <1,000 m, (2) altitudes between 1,000 and 2,500 m, and (3) altitudes ≥2,500 m, and modeled the relationship between cases per capita with respect to the district's altitude in each group. In the lower range (Fig. 1A), a significant inverse relationship is observed in line with a previous study in which a coarser granularity level was used (Segovia-Juarez et al., 2020). By contrast, in the medium- and high-altitude ranges, the observed association of altitude and cases for COVID-19 was not maintained. Whereas the data from altitudes <1,000 m demonstrate an inverse relationship (R2 = 0.0362; p < 0.001), and for data from 1,000 to 2,500 m (Fig. 1B, R2 = 0.0016; p = 0.537), and for altitudes > 2,500 m (Fig. 1C, R2 = 0.0027; p = 0.120), this association disappeared. It should be noted that very low R2 value for the data < 1,000 m demonstrates that altitude can only explain ∼3% of the totality variability. In addition, the fact that higher altitudes are not associated with increased infection and mortality suggests that the positive association found over a very low altitude range may be a false positive finding.
FIG. 1. Association between per capita COVID-19 cases (at the district level) in Peru in relation to altitude (meters). (A) Altitudes <1,000 m. (B) Altitudes from 1,000 to <2,500 m. (C) Altitudes from 2,500 m to higher. Each figure includes coefficient of variation (R2), p-value, number of districts, and number of COVID-19 cases. Source: MINSA (2020). Population and altitude in each district were obtained from INEI (2019). COVID-19, coronavirus disease.
These results suggest that factors associated with increasing altitude such as ultraviolet B radiation, hypoxia, low temperature, aridity, and high hemoglobin levels might not afford protection against COVID-19 infection. The observed change in infection rates at low altitudes might be associated with factors such as high population density, large populations, and perhaps exposure to greater air pollution, such as PM2.5 particulates (Pun et al., 2020; Vásquez-Apestegui et al., 2020).
Believing that altitude might protect against COVID-19 infection and mortality might lead people to become overconfident and engage in behaviors that could reduce the effectiveness of protective measures such as physical distancing, washing hands, mask wearing, and avoiding large gatherings of people.
In conclusion, our data demonstrate that high altitude does not protect against COVID-19 infection and mortality.

References

Arias-Reyes C, Zubieta-DeUrioste N, Poma-Machicao L, Aliaga-Raduan F, Carvajal-Rodriguez F, Dutschmann M, Schneider-Gasser EM, Zubieta-Calleja G, and Soliz J. (2020). Does the pathogenesis of SARS-CoV-2 virus decrease at high-altitude? Respir Physiol Neurobiol 277:103443.
INEI. (2019). National Directory of Province, District and Population Center Municipalities. https://www.inei.gob.pe/media/MenuRecursivo/publicaciones_digitales/Est/Lib1653/index.html (accessed on August 17, 2020).
MINSA. (2020). Positives cases for COVID-19—[Ministry of Health—MINSA]. https://www.datosabiertos.gob.pe/dataset/casos-positivos-por-covid-19-ministerio-de-salud-minsa (accessed on August 17, 2020).
Pun M, Turner R, Strapazzon G, Brugger H, and Swenson ER. (2020). Lower incidence of COVID-19 at high altitude: facts and confounders. High Alt Med Biol 21:217–222.
Segovia-Juarez J, Castagnetto JM, and Gonzales GF. (2020). High altitude reduces infection rate of COVID-19 but not case-fatality rate. Respir Physiol Neurobiol 281:103494.
Vasquez-Apestegui V, Parras-Garrido E, Tapia V, Paz-Aparicio VM, Rojas JP, SÃnchez-Ccoyllo OR, Gonzales GF. (2020). Association between air pollution in Lima and the high Incidence of COVID-19: findings from a post hoc analysis. Res Sq [Epub ahead of print].
Woolcott OO, Bergman RN. (2020). Mortality Attributed to COVID-19 in High-Altitude Populations. High Alt Med Biol 21:409–416.

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cover image High Altitude Medicine & Biology
High Altitude Medicine & Biology
Volume 21Issue Number 4December 2020
Pages: 428 - 430
PubMed: 33054403

History

Published online: 21 December 2020
Published in print: December 2020
Published ahead of print: 13 October 2020
Accepted: 18 September 2020
Received: 17 September 2020

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Jesus M. Castagnetto
University Informatics and Systems Office, Universidad de Lima, Lima, Peru.
Jose Segovia-Juarez
Department of Computer Science, Universidad Nacional de Ingeniería, Lima, Peru.
Gustavo F. Gonzales [email protected]
High Altitude Research Institute, Laboratories of Investigation and Development (LID), Department of Biological and Physiological Sciences, Faculty of Sciences and Philosophy, Universidad Peruana Cayetano Heredia, Lima, Peru.

Notes

Address correspondence to: Gustavo F. Gonzales, MD, High Altitude Research Institute, Laboratories of Investigation and Development (LID), Department of Biological and Physiological Sciences, Faculty of Sciences and Philosophy, Universidad Peruana Cayetano Heredia, Av. Honorio Delgado 430, Lima 31, Peru [email protected]

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No competing financial interests exist.

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This research has received no external funding.

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