https://www.cidrap.umn.edu/covid-19...ps-bolivia-had-lowest-covid-death-rates-world
Researchers probe why 2 Indigenous groups in Bolivia had lowest COVID death rates in world
Mary Van Beusekom, MS
Today at 8:57 a.m.
COVID-19
For the study, published in Social Science & Medicine, a team led by researchers from the Universita di Corsica in France interviewed and took blood samples from members of the Tsimane and Moseten communities aged 17 years and older in July and December 2020 and March through May 2021.
Deaths were vanishingly rare, at 0.009% among the Tsimane and 0.095% among the Moseten.
“The fact that the fatality rate was very, very low, was a bit of a head scratcher,” anthropologist and corresponding author Michael Gurven, PhD, of the University of California (UC) Santa Barbara, said in a UC news release. He co-directs the Tsimane Health and Life History Project.
Good baseline health
Gurven worried about Tsimane people, because historically many Indigenous groups have been devastated by introduced pathogens due to factors such as immunologic naivety to infectious agents, high rates of transmission within tight-knit communities, and poor access to medical care, medicine, and vaccines.
Indeed, Indigenous communities with a high prevalence of chronic conditions, such as the Dine in the southwestern United States, experienced high COVID-19 death rates.
Anticipating poor outcomes, the researchers worked with Indigenous leaders and local health officials to slow SARS-CoV-2 transmission infection through actions such as voluntary collective isolation, in which the groups abstained from making contact with outsiders. After SARS-CoV-2 arrived in the communities, the team began monitoring how fast the virus spread, who got infected, and symptom severity and duration.
The Tsimané still experienced that first stage of COVID, but they never quite got to that second stage where it enters your lungs, when people experienced cytokine storms and sometimes needed to be hooked up to a respirator.
Michael Gurven, PhD
The virus quickly spread to 71.4% of the 685 Tsimane sampled and 63% of the 562 Moseten, and infected people reported the same kinds of symptoms that people were experiencing worldwide.
“The Tsimané still experienced that first stage of COVID, but they never quite got to that second stage where it enters your lungs, when people experienced cytokine storms and sometimes needed to be hooked up to a respirator,” he said. “In fact, we had struggled to find and set up oxygen concentrators because we were worried, especially for the older adults, but there was no need to even use them.”
The Tsimane and Moseten are Indigenous subsistence populations in northern and eastern Bolivia that are physically fit into old age, consume diets based on horticulture and foraging, and have low rates of obesity and minimal cigarette smoking and illicit drug use. They also have remarkably low levels of the cardiovascular diseases (such as high blood pressure), inflammation, and diabetes that can lead to severe COVID-19 complications.
On the other hand, the groups have high rates of parasitism and infectious disease, including disease and death due to respiratory infections such as tuberculosis.
“Preceding and during the initial wave of SARS-CoV-2 in 2020, there were reasons to expect that the Tsimane and Moseten might be particularly vulnerable to the impacts of COVID-19,” the researchers wrote. “Of particular concern was the welfare of elders, who serve important roles as transmitters of cultural practices and traditions.”
1/23rd the expected death rate
The experience of the Tsimane and Moseten during the initial 2020 pandemic wave contrasts sharply with that seen in more industrialized regions. Although 71% and 63% of the tribes contracted COVID-19, case-fatality rates were 0.009% among the Tsimane and 0.095% among the Moseten. And during the study period, just three community members (all men older than 65) died.
The death rate for the Tsimane was 1/23rd the expectation based on rates documented elsewhere in the world—a finding that relative youth and low rates of chronic conditions couldn’t explain. Illness severity, as determined by length of illness, enzyme-linked immunosorbent assay (ELISA) antibody levels, and virus-neutralizing test concentrations—rose only slightly with age.
An understanding of how background pathogen exposure and hygienic environments play a role in decreased immune effectiveness with age, and how those factors interact with chronic noncommunicable diseases, is clearly in order.
Blood tests showed that levels of COVID-specific antibodies were more than double those measured in a French cohort during the same COVID wave. While post-infection antibody levels couldn’t account for the low death rate, they could indicate a more vigorous immune response earlier in the disease course that fought off the virus in its initial flu-like phase. The tests also revealed high concentrations of infection-fighting white blood cells.
The researchers said the groups’ persistent exposure to pathogens amid a lack of sanitation and abundant parasites and bacterial infections may help maintain readiness to mount a strong immune response.
In contrast, relatively hygienic industrial societies don’t expose people to the same diversity of pathogens, meaning that their immune systems aren’t as primed to fight off infections. “With us, the immunity can be overly responsive, and to non-pathogens—so we see far more cases of allergies and autoimmune diseases than groups like the Tsimané,” Gurven said.
Thus, many factors likely contributed to Tsimane and Moseten COVID-19 resilience. “So we shouldn’t be looking for a single magic bullet,” Gurven said. “And if there are lessons to learn that might generalize to conditions that are favorable toward being protected against infectious disease, well, that’s great. We need that.”
The authors said that, given the inevitability of future pandemics, a better understanding of the factors that influence vulnerability and resilience is of great import. “An understanding of how background pathogen exposure and hygienic environments play a role in decreased immune effectiveness with age, and how those factors interact with chronic noncommunicable diseases, is clearly in order,” they concluded.
Researchers probe why 2 Indigenous groups in Bolivia had lowest COVID death rates in world
Mary Van Beusekom, MS
Today at 8:57 a.m.
COVID-19
Two Indigenous groups in Bolivian Amazon had the lowest COVID-19 death rates ever reported in the height of the pandemic—less than one-tenth of 1%—despite high rates of infection and severe disease—a finding that researchers say has implications for disease-mitigation efforts in future pandemics.For the study, published in Social Science & Medicine, a team led by researchers from the Universita di Corsica in France interviewed and took blood samples from members of the Tsimane and Moseten communities aged 17 years and older in July and December 2020 and March through May 2021.
Deaths were vanishingly rare, at 0.009% among the Tsimane and 0.095% among the Moseten.
“The fact that the fatality rate was very, very low, was a bit of a head scratcher,” anthropologist and corresponding author Michael Gurven, PhD, of the University of California (UC) Santa Barbara, said in a UC news release. He co-directs the Tsimane Health and Life History Project.
Good baseline health
Gurven worried about Tsimane people, because historically many Indigenous groups have been devastated by introduced pathogens due to factors such as immunologic naivety to infectious agents, high rates of transmission within tight-knit communities, and poor access to medical care, medicine, and vaccines.
Indeed, Indigenous communities with a high prevalence of chronic conditions, such as the Dine in the southwestern United States, experienced high COVID-19 death rates.
Anticipating poor outcomes, the researchers worked with Indigenous leaders and local health officials to slow SARS-CoV-2 transmission infection through actions such as voluntary collective isolation, in which the groups abstained from making contact with outsiders. After SARS-CoV-2 arrived in the communities, the team began monitoring how fast the virus spread, who got infected, and symptom severity and duration.
The Tsimané still experienced that first stage of COVID, but they never quite got to that second stage where it enters your lungs, when people experienced cytokine storms and sometimes needed to be hooked up to a respirator.
Michael Gurven, PhD
The virus quickly spread to 71.4% of the 685 Tsimane sampled and 63% of the 562 Moseten, and infected people reported the same kinds of symptoms that people were experiencing worldwide.
“The Tsimané still experienced that first stage of COVID, but they never quite got to that second stage where it enters your lungs, when people experienced cytokine storms and sometimes needed to be hooked up to a respirator,” he said. “In fact, we had struggled to find and set up oxygen concentrators because we were worried, especially for the older adults, but there was no need to even use them.”
The Tsimane and Moseten are Indigenous subsistence populations in northern and eastern Bolivia that are physically fit into old age, consume diets based on horticulture and foraging, and have low rates of obesity and minimal cigarette smoking and illicit drug use. They also have remarkably low levels of the cardiovascular diseases (such as high blood pressure), inflammation, and diabetes that can lead to severe COVID-19 complications.
On the other hand, the groups have high rates of parasitism and infectious disease, including disease and death due to respiratory infections such as tuberculosis.
“Preceding and during the initial wave of SARS-CoV-2 in 2020, there were reasons to expect that the Tsimane and Moseten might be particularly vulnerable to the impacts of COVID-19,” the researchers wrote. “Of particular concern was the welfare of elders, who serve important roles as transmitters of cultural practices and traditions.”
1/23rd the expected death rate
The experience of the Tsimane and Moseten during the initial 2020 pandemic wave contrasts sharply with that seen in more industrialized regions. Although 71% and 63% of the tribes contracted COVID-19, case-fatality rates were 0.009% among the Tsimane and 0.095% among the Moseten. And during the study period, just three community members (all men older than 65) died.
The death rate for the Tsimane was 1/23rd the expectation based on rates documented elsewhere in the world—a finding that relative youth and low rates of chronic conditions couldn’t explain. Illness severity, as determined by length of illness, enzyme-linked immunosorbent assay (ELISA) antibody levels, and virus-neutralizing test concentrations—rose only slightly with age.
An understanding of how background pathogen exposure and hygienic environments play a role in decreased immune effectiveness with age, and how those factors interact with chronic noncommunicable diseases, is clearly in order.
Blood tests showed that levels of COVID-specific antibodies were more than double those measured in a French cohort during the same COVID wave. While post-infection antibody levels couldn’t account for the low death rate, they could indicate a more vigorous immune response earlier in the disease course that fought off the virus in its initial flu-like phase. The tests also revealed high concentrations of infection-fighting white blood cells.
The researchers said the groups’ persistent exposure to pathogens amid a lack of sanitation and abundant parasites and bacterial infections may help maintain readiness to mount a strong immune response.
In contrast, relatively hygienic industrial societies don’t expose people to the same diversity of pathogens, meaning that their immune systems aren’t as primed to fight off infections. “With us, the immunity can be overly responsive, and to non-pathogens—so we see far more cases of allergies and autoimmune diseases than groups like the Tsimané,” Gurven said.
Thus, many factors likely contributed to Tsimane and Moseten COVID-19 resilience. “So we shouldn’t be looking for a single magic bullet,” Gurven said. “And if there are lessons to learn that might generalize to conditions that are favorable toward being protected against infectious disease, well, that’s great. We need that.”
The authors said that, given the inevitability of future pandemics, a better understanding of the factors that influence vulnerability and resilience is of great import. “An understanding of how background pathogen exposure and hygienic environments play a role in decreased immune effectiveness with age, and how those factors interact with chronic noncommunicable diseases, is clearly in order,” they concluded.