# 8135
The 1918 H1N1 pandemic – which is estimated to have killed roughly 2% of those infected in Europe and North America – wreaked far greater havoc in other regions of the world, and proved absolutely devastating among some remote indigenous populations.
In the 2012 EID Journal article Differential Mortality Rates by Ethnicity in 3 Influenza Pandemics Over a Century, New Zealand, the authors from the University of Otago in Wellington, New Zealand wrote:
Evidence suggests that indigenous populations have suffered disproportionately from past influenza pandemics. To examine any such patterns for Māori in New Zealand, we searched the literature and performed new analyses by using additional datasets. The Māori death rate in the 1918 pandemic (4,230/100,000 population) was 7.3× the European rate. In the 1957 pandemic, the Māori death rate (40/100,000) was 6.2× the European rate.
In the 2009 pandemic, the Māori rate was higher than the European rate (rate ratio 2.6, 95% confidence interval 1.3–5.3). These findings suggest some decline in pandemic-related ethnic inequalities in death rates over the past century. Nevertheless, the persistent excess in adverse outcomes for Māori, and for Pacific persons residing in New Zealand, highlights the need for improved public health responses.
From the HHS sponsored 1918 pandemic documentary We Heard The Bells, we get this account of the impact among native Americans in Alaska and the American Southwest.
NARRATOR:
There were few communities in the U.S. so small or isolated that they were sheltered from the waves of deadly disease that swept around the world. The influenza of 1918 even touched remote Inuit villages in Alaska, sometimes killing every man, woman, and child…or killing the adults and leaving the children with no one to care for them. The 1918 influenza struck some native peoples in the Southwest very hard, too.
And in 2011, in Study: Urban vs Rural Mortality From Spanish Flu, we looked at a Norwegian study that found the mortality rate in 1918 varied nearly 100 fold between remote, rural regions and urban populations, and that in the more remote areas, older persons were just as susceptible to the virus as those who were younger.
All of which serves a prelude to a new study appearing in PNAS, that looks at the vulnerability of some indigenous peoples to pandemic flu (specifically H7N9), and finds their innate immune response is not as finely tuned to fighting off influenza as people of Caucasian extraction.
While most of the world’s population lacks specific antibodies against H7N9 due to lack of previous exposure, and are assumed to be highly susceptible to infection, our innate immune system has a number of tools to help fight off infections once we acquire them.
- phagocytic cells (neutrophils, monocytes, and macrophages);
- cells that release inflammatory mediators (basophils, mast cells, and eosinophils);
- natural killer cells (NK cells); and
- molecules such as complement proteins, acute phase proteins, and cytokines.
In other words, our innate immune system throws just about everything but the kitchen sink at an unknown infection, and CD8+ T-Cells are part of that generic defense system. But, as the study below indicates, the ability to mount this particular defense varies among different ethnicities.
Preexisting CD8+ T-cell immunity to the H7N9 influenza A virus varies across ethnicities
Sergio Quiñones-Parraa, Emma Granta, Liyen Loha, Thi H. O. Nguyena,b, Kristy-Anne Campbellc, Steven Y. C. Tongd, Adrian Millere, Peter C. Dohertya,f,1, Dhanasekaran Vijaykrishnag, Jamie Rossjohnc,h, Stephanie Grasc, and Katherine Kedzierskaa,1
Significance
The severity of the novel H7N9 influenza A virus (IAV) and the lack of neutralizing antibodies raise real pandemic concerns. In this scenario, CD8+ T lymphocytes (CTLs) may provide a layer of protection against the H7N9 virus. Our study dissects the extent of preexisting CTL immunity with the potential to respond to H7N9.
We identified conserved immunogenic peptides with the capacity to elicit robust CTL responses against any human IAV, including the H7N9 virus, as well as the mutations that abolish CTL recognition. The human leukocyte antigen class I molecules that present these peptides vary in prevalence depending on the ethnicity. Such analyses found that the Alaskan and Australian Indigenous people may be particularly vulnerable to the H7N9 influenza disease.
For more on this, we turn to a feature in The Australian, with an interview one of the authors, Dr. Peter Doherty.
Aborigines 'most vulnerable' to bird flu strain
EUROPEANS may have better immune defences than other ethnic groups when facing the latest potential pandemic bird flu from China.
A study published today in the journal PNAS suggests Aborigines and other indigenous groups with a history of isolation may be most at risk if the bird flu H7N9 begins to spread widely among humans.
And Europeans may be best placed to survive any pandemic because of a long history of exposure to influenza viruses.
"There's a genetics of resistance that has evolved in western populations, we think," said Nobel prize winner Peter Doherty, whose Melbourne University colleague Katherine Kedzierska led the research team.
Professor Doherty ranks Europeans, followed by Asians and Africans, as having the most developed innate flu response, and Australian Aborigines and indigenous Alaskans as having the least.
You may recall that last month I featured a study by Professor Doherty (see PNAS: Genetic Marker & Cytokine Levels Linked To Severity Of Human H7N9 Infection) that linked a specific genetic marker; IFITM3 CC gene variant (aka C/C Genotype) to hypercytokinemia (aka a `Cytokine Storm’), and a severe outcome, in H7N9 infections.
This genetic marker– while relatively rare in Caucasians - is much more common in Han Chinese.
While the variant C/C genotype was over represented among seriously ill patients (compared to its prevalence in the local population), and the C/C genotype was also linked to more rapid disease progression than with the others, that severe disease was also seen with other genotypes.
So it doesn’t mean that if you have one of the other genotypes, you are guaranteed an easy time of it. But your odds of a bad outcome appear to go up with the C/C genotype.
All of which illustrates that there are probably a number of variables – some we know about, and others we have yet to discover – that help explain why pandemic influenza varies in intensity around the globe.
