[MCN] Will climate & environmental changes expose today's young to increased risk of diseases? Cause for optimism?

[Lance Olsen]

Medical News Today.  April 3, 2020

How might climate change affect the spread of viruses?
<<https://www.medicalnewstoday.com/articles/how-might-global-warming-influence-the-spread-of-viruses <https://www.medicalnewstoday.com/articles/how-might-global-warming-influence-the-spread-of-viruses>>>

Excerpts :

In the coming decades, ecological degradation, rising temperatures, and extreme weather events could intensify the threats to human health posed by viruses.

We know from past epidemics that changes in temperature, rainfall, and humidity can have profound effects on the spread of infectious disease <https://www.atsjournals.org/doi/full/10.1513/AnnalsATS.201511-729PS>.

Between 1793 and 1905, there were nine devastating yellow fever epidemics. Seven coincided with a major El Niño episode.

El Niño is a band of warm water that develops off the Pacific coast of South America every 4 years or so. The phenomenon results in high rainfall, warm springs, and hot summers in southern U.S. states.

According to research published in the Bulletin of the American Meteorological Society <https://journals.ametsoc.org/doi/abs/10.1175/1520-0477(1999)080%3C0021:APCBTY%3E2.0.CO%3B2> in 1999, this provided the perfect conditions for A. aegypti to spread yellow fever.

The El Niño event coinciding with the 1878 epidemic was one of the strongest on record.

A taste of things to come
Predicting how future climate change will influence the spread of viral infections is fraught with difficulty. This is due to the complexity of interactions between climate, nature, and human activity.

But annual fluctuations in some viral infections, such as seasonal flu, and historical epidemics, such as yellow fever, provide some clues.

According to the Intergovernmental Panel on Climate Change <https://www.ipcc.ch/sr15/resources/headline-statements/>, human activity has already caused approximately 1.0°C of global warming above pre-industrial levels. If warming continues at its current rate, temperatures will reach 1.5°C above these levels between 2030 and 2052.

As a result, there is likely to be more extreme weather, including more droughts, flooding, and heatwaves. Changes in temperature, rainfall, and humidity will have numerous knock-on effects on the world’s animals and ecosystems.

According to a report by the World Health Organization (WHO) <https://www.who.int/globalchange/publications/climatechangechap6.pdf>, “Climate change, one of the global environmental changes now underway, is anticipated to have a wide range of impacts upon the occurrence of infectious disease in human populations.”

Infectious diseases that people catch from animals are known as zoonoses.

As the authors of an article in the journal Annals of the American Thoracic Society <https://www.atsjournals.org/doi/full/10.1513/AnnalsATS.201511-729PS> point out that if climate change displaces wild animals, they will bring their zoonoses with them.

Changes in rainfall and temperature, for example, can affect the availability of food eaten by animal hosts, such as bats, chimps, pangolin, and deer. The resulting changes in the size and range of their populations may bring them into closer contact with humans.

In late 1999 and early 2000, scientists in Los Santos in Panama identified the first ever cases in Central America of hantavirus pulmonary syndrome <https://www.cdc.gov/mmwr/preview/mmwrhtml/mm4910a2.htm>.

This potentially fatal lung disease is a zoonosis caused by a virus shed in the saliva, urine, and feces of rodents.

A report in Emerging Infectious Diseases <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3320309/> pins the blame for the outbreak on a two- to three-fold increase in rainfall in Los Santos in September and October 1999, which led to an explosion in rodent numbers.

Excess rainfall may also indirectly promote the spread of enteroviruses that affect millions of people worldwide every year. Humans transmit enteroviruses, including poliovirus, coxsackie, and echovirus, to other people via the fecal-oral route.

For example, climate change can cause flash floods on land and sweep human sewage into the sea. When this happens, some of these viruses might contaminate shellfish, for example, leading to higher levels of disease in humans.

Human behavior
The U.S. Centers for Disease Control and Prevention (CDC) <https://www.cdc.gov/onehealth/basics/zoonotic-diseases.html> estimate that three out of every four new or emerging diseases come from animals.

Experts have linked the earliest cases of COVID-19 to the Huanan “wet” market in Wuhan province, China, where people sold wild animals for meat.

A new study published in Nature <https://www.nature.com/articles/s41591-020-0820-9> has confirmed that novel coronavirus was not made in a laboratory, as some conspiracy theories had suggested. Rather, its genome bears a striking resemblance to bat coronaviruses, and it is similar to coronaviruses that infect pangolins.

This is consistent with the theory that the virus spread to humans from bats via the pangolins sold in the Huanan market.

While there is no suggestion that climate change played any role in the emergence of COVID-19, it may have a knock-on effect on the type of human activity that brings wild animals and people into closer contact, particularly when food is in short supply.

For example, if crops fail and livestock perishes due to increased flooding, droughts, heatwaves, or pests, hunger may drive people to hunt and eat more wild animals.

Something similar may have led to the emergence of Ebola, a particularly infectious and deadly virus, in a village deep in the Minkebe Forest in northern Gabon in 1996 <https://www.nytimes.com/1996/02/20/world/ebola-killed-13-in-gabon-who-says.html>.

Experts believe that the outbreak was due to the villagers killing an eating a chimpanzee. Scientists linked a later outbreak that began in 2007 <https://www.theatlantic.com/health/archive/2014/07/where-does-ebola-come-from/375206/> in West Africa to eating fruit bats.

The destruction of pristine forest ecosystems by logging and other human incursions may also increase the risk that other viruses will leap from wild animals into people.

According to another study published in Nature <https://www.nature.com/articles/nature09575?page=12#auth-1>, degraded habitats harbor more of the viruses that can infect humans. This may be because biodiversity loss “amplifies” viral infections in the remaining species.

The scientists write:“In principle, loss of biodiversity could either increase or decrease disease transmission. However, mounting evidence indicates that biodiversity loss frequently increases disease transmission.”

An analysis of influenza in the U.S. between 1997 and 2013, for example, found that warm winters were followed by earlier, more severe flu seasons the next year.

The paper in PLOS Currents: Influenza <http://currents.plos.org/influenza/article/climate-change-and-influenza-the-likelihood-of-early-and-severe-influenza-seasons-following-warmer-than-average-winters/> suggests that mild winters may reduce “herd immunity <https://apic.org/monthly_alerts/herd-immunity/>” because fewer people are contracting the virus. This makes it easier for the virus to spread the following year, resulting in worse outbreaks.

The authors of a study published this year in IOPscience <https://iopscience.iop.org/article/10.1088/1748-9326/ab70bc> warn that rapid fluctuations in temperature — a characteristic of global warming — impair the immune system’s ability to fight off respiratory infections.

The scientists write:“[Climate models suggest] that the rapid weather variability in autumn will continue to strengthen in some regions of northern mid-latitudes in a warming climate, implying that the risk of an influenza epidemic may increase 20% to 50% in some highly populated regions in the later 21st century.”

Cause for optimism?
There is concern that a changing climate will bring more viral disease outbreaks. However, although outbreaks may become more frequent, science is in a better place to counter them.

Recent technological advances mean that scientists can develop and manufacture diagnostic tests and vaccines at a speed that would have been unthinkable just a decade ago.

However frustratingly slow the response to COVID-19 may feel at the moment, a situation such as this would have been worse a decade ago, when it could take 10-15 years <https://www.historyofvaccines.org/content/articles/vaccine-development-testing-and-regulation> to develop a vaccine. Now, scientists are hopeful of having a vaccine against SARS-CoV-2 within the next 12-18 months.

An analysis of infectious disease outbreaks published by Journal of the Royal Society Interface <https://royalsocietypublishing.org/doi/full/10.1098/rsif.2014.0950> in 2014 concluded:

“Our data suggest that, despite an increase in overall outbreaks, global improvements in prevention, early detection, control, and treatment are becoming more effective at reducing the number of people infected.”

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Financial Times - March 28, 2018
Special Report <https://www.ft.com/reports>

How to make a carbon pricing system work
Compensation for those who lose out and sanctions on non-compliance are needed
MARTIN WOLF <https://www.ft.com/martin-wolf>

<<https://www.ft.com/content/2d9490f2-1291-11e8-a765-993b2440bd73 <https://www.ft.com/content/2d9490f2-1291-11e8-a765-993b2440bd73>>>

1st 2 sentences

“Carbon pricing is a good idea whose time has not yet come. But it has to do so.”

Closing paragraph

“Until now, therefore, carbon pricing remains a sleeping giant. Yet needed progress will not be achieved if it does not awake. The difficulties in meeting agreed objectives in our fractured world are enormous. The chances are high that the effort will fail. If so, our goose will be cooked.”



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