The coronavirus puzzle at height

An Aymara woman with a face mask in La Paz (Bolivia), in April 2020.Martín Alipaz (EFE)

Does the coronavirus lose strength at height?

Since the outbreak of the pandemic, multiple studies have emerged that confirm and refute it.

Some have received space in prestigious scientific journals such as

and

, international media such as

and

and medical repositories such as that of the US National Institutes of Health. But more often than not, paper titles and footnotes are accompanied by question marks, an inescapable mark of the skepticism that prevails in the international community.

The issue is complex and intertwines environmental, physiological, genetic and social factors.

Latin America —particularly the Andean countries— has been one of the leaders in research into the complicated relationship between covid-19 and altitude: three South American capitals are above 2,500 meters above sea level and some 20 Millions of Latin Americans live in one of the 30 highest cities in the region.

Several Andean specialists use a metaphor to explain their findings, saying that the coronavirus suffers from

, as the discomfort felt when being at high altitudes due to lack of oxygen is called in the region.

Bolivian doctor Gustavo Zubieta, one of the first scientists to analyze the issue, explains that the forecasts for the countries along the Andes mountain range were not very encouraging at the beginning of the pandemic.

“Almost all the scientists affirmed that the covid at altitude was going to be terrible due to the lower amount of oxygen produced by lower barometric pressure,” says Zubieta, director of the Pulmonary and Pathology Institute at Height.

The statistics, however, did not reflect the devastating effect that had been anticipated.

On the contrary.

In Bolivia, the health authorities identified that the cases were concentrated, at least initially, in low-lying areas such as Santa Cruz, as well as in the Amazon regions that border Brazil.

The same thing happened in Peru, where the number of deaths and infections was substantially lower when comparing high and low cities with the same population.

From there a chain reaction arose and statements from officials and studies appeared in Ecuador, Colombia and even Brazil, among others.

Zubieta lists a series of environmental factors that, according to his work, seem to influence a slower spread of the coronavirus: ultraviolet radiation, which acts as a sterilant against many bacteria and viruses;

lower humidity, which creates drier and less favorable environments for the virus, and lower atmospheric pressure, which helps the particles to disperse.

But other factors also come into play.

Above 2,500 meters, the body has to produce more red blood cells to compensate for the lack of oxygen (hypoxia) because the atmospheric pressure is lower.

The researcher says that the inhabitants of high areas are adapted to these conditions and that this may mean better protection against the drop in oxygen saturation that the coronavirus usually causes.

View of Pujilí, an Ecuadorian town settled in the Andes mountain range, at almost 2,900 meters above sea level.Edu León

It is also cited that at height there is usually a lower number of ACE-2 receptors, the door that SARS-CoV-2 uses to enter cells.

Zubieta also studies the functioning of the mitochondria, responsible for cellular respiration, and ensures that they are more efficient in the inhabitants of highlands.

"We are about to publish a study with researchers from Bolivia, Colombia, Peru, Ecuador and Mexico that confirms that there is much lower mortality from covid in higher areas and a higher incidence of cases in areas below 1,000 meters," she says.

Esteban Ortiz Prado, an academic from the University of the Americas, has also studied the relationship between covid-19 and height, but has reached different conclusions.

"Covid is less prevalent and less deadly in highlands, when corrected for comorbidities," says the Ecuadorian specialist, although he adds that the lower incidence has more to do with lower population density and with certain patterns of coexistence of people of high areas.

Ortiz Prado says that physiological theories, such as the lower number of ACE-2 receptors, and about certain environmental factors such as UV rays, have lost explanatory ground and have not been proven.

“It is not that a person who gets sick at sea level automatically improves when they reach a higher region, on the contrary,” explains Ortiz Prado, but he maintains that there may be some acclimatization and adaptation before contracting the infection.

"We know for a fact that our bodies work differently at altitude," says the doctor.

He and a group of scientists analyzed data on excess mortality in Ecuador from March 2020 to March 2021 and found that the number of deaths per 100,000 inhabitants in areas less than 1,500 meters above sea level was twice as high. than in very high areas, above 3,500 meters.

Some of the criticisms of studies on the virus and altitude, especially those based on environmental factors, are jumping to conclusions without sufficient evidence, questioning causal factors and possible confounding variables, that is, they make more noise what they explain.

“We must avoid jumping to the conclusion that any community has innate protection against covid-19 in the absence of robust evidence,” reads a paper signed in 2020 by Matiram Pun and a team of researchers in Canada.

"Possible biological mechanisms remain speculative," said the Peruvian-trained doctor Orison Woolcott and the American researcher Richard N. Bergman, in an exchange of correspondence with Zubieta in the journal

.

Woolcott and Bergman stated in 2020 that there was a higher mortality among Mexican patients over 65 years of age who lived above 1,500 meters, although it is below the standard classification of 2,500 meters.

Other academics are investigating whether some treatments used for altitude sickness can help treat covid or if, on the contrary, they make it worse.

From a perspective that is not necessarily scientific, one question that arises is whether there is an obsession with seeking explanations in the heights associated with Andean identity, and that is often reflected in less serious discussions such as the World Cup qualifiers.

Zubieta, who has four decades of experience on the subject, laughs and then categorically denies it: "It's not an obsession, it's a reality."

“Most of the people who discredit these jobs are because they don't know these environments or have never been here,” he says.

"Many times it is seen as a disadvantage to live in these conditions, when in reality it implies several advantages."

"I don't think everything has an answer at height," Ortiz Prado clarifies.

The researcher points out that height is not a factor in leading countries in scientific research such as the United States and the United Kingdom, and believes that this partly explains the resistance and that the subject is relegated.

The specialist says that the largest number of studies in this regard come from mountain tourism and sports, but that there are not many resources nor has there been so much in-depth study of populations that live permanently in these conditions.

The topic has been a markedly Latin American discussion, but not exclusive to the region.

There are studies in places like Switzerland, Austria and Tibet, for example, looking for hypotheses in altitude sickness medicine about covid-19.

There is no great consensus or universally accepted conclusions.

Caution and preliminary results prevail.

The debate, however, is a reflection of the overwhelming response of science to the pandemic, the challenge of the speed at which scientific information has flowed in the last two years and the long way that remains to be discovered about the virus.

"There is much to be done and the freedom we have to develop theories and investigate them cannot be undermined," Ortiz Prado defends.

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