How climate change and globalization are linked to viruses and new diseases
As humans have spread across the world, so have infectious diseases. The more civilized we became and increased contact with different populations of people and animals, the more pandemics occured. Zoonosis, the transmission of infectious disease from animals to humans or viceversa, led to the influenza pandemic, HIV, Covid, and now monkeypox, among many others, and according to experts, it will keep happening.
The bat in the image (the "flying fox" that eats fruit and lives in parts of Africa, Asia and Oceania) is the reservoir (place of refuge) of a virus that spreads easily and kills profusely. According to WHO data, Nipah has a mortality rate of between 40% and 70%.
Image: From user:Raul654 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=529930
Two factors increase the dangers of Nipah. First of all, pigs are especially vulnerable to the virus and it is easier for the infection to spread from pig to human. Secondly: it incubates for more than a month without symptoms and during that period it can become contagious.
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Nipah outbreaks have been inconsequential so far, with most of them located in Asia. Nevertheless, scientists have seen some alarm bells. An example collected by the BBC: In Bangladesh, there were 196 cases of Nipah between 2001 and 2011, and of those infected, 150 people died.
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Climate change and globalization encourage tropical diseases to travel to other parts of the planet and spread. The mosquito in the image (aedes aegypti) transmits dengue. This disease causes high fever, severe joint pain (in some countries they call dengue "bone fever") and, in its most severe form, hemorrhages that can cause death.
The WHO admits that dengue has multiplied its incidence in recent times. According to their data, before 1970 only nine countries had suffered dengue epidemics and now there are more than 100 where the disease is endemic. Even very far from tropical climates, as is the case in Europe.
A WHO report says: "Europe is currently facing the possibility of dengue outbreaks; in 2010, local transmission of the disease was reported for the first time in France and Croatia, and imported cases were detected in three other European countries. In 2012, an outbreak of dengue in the Madeira archipelago (Portugal) caused more than 2,000 cases, and imported cases were detected in 10 other European countries, in addition to mainland Portugal."
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The Zika virus was first detected in macaques, specifically in Uganda. It is inoculated by a mosquito and causes mild symptoms (fever, perhaps a skin rash, muscle aches...). The infected person can even be asymptomatic. But if the virus reaches a pregnant woman, the consequences for that child can be terrible.
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The Zika virus in pregnant women causes malformations, especially microcephaly. It is usually accompanied by brain damage and there is a high possibility that it will cause the death of the newborn in 10 days.
Image: From Centers for Disease Control and Prevention - https://www.cdc.gov/ncbddd/birthdefects/images/microcephaly-comparison-500px.jpg, Public Domain, https://commons.wikimedia.org/w/index .php?curid=46674502
The WHO reports on its website that the first major outbreak of Zika occurred on the island of Yap in Micronesia in 2007. In 2013 there was another major outbreak in Polynesia and in 2015 it broke out in Brazil. But there are already cases all over the world. Spain, France, Germany or the United Kingdom have detected Zika infections in recent years.
Some experts attribute the great outbreak of Zika in Brazil to the deforestation of the Amazon and the irruption of large human groups in previously wild areas, facilitating zoonosis.
The so-called West Nile virus landed in New York in 1999 and caused an outbreak that spread across the United States. The natural hosts for this virus are birds and mosquitoes. Yet another case of zoonosis.
Over 300 different species of bird have been shown to be infected with West Nile virus. From sparrows or magpies to pigeons or finches. When a mosquito bites this bird and then a human, infection occurs.
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It's not one of the viruses with the highest mortality, but, according to the WHO, one in 150 cases becomes serious and leads to the so-called "Nile fever", which can kill vulnerable patients. It happened in two towns in the south of Spain, where an outbreak occurred in 2020 with 176 infected people and seven fatalities.
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Many of the diseases described above spread because temperatures are rising in many parts of the globe, aquifers are drying up and species ( mainly mosquitoes) are invading areas that they did not frequent before.
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An infected tick can transmit Lyme disease, which if left untreated can spread to vital organs. Global warming and urbanization in unsuitable natural areas have led to an expanded range of ticks, increasing the risk of Lyme disease.
Image: From Photo by Scott Bauer. - This image was released by the Agricultural Research Service, the research agency of the United States Department of Agriculture, with the ID k8002-3 (next)., Public Domain, https://commons.wikimedia.org/w/index. php?curid=363940
Lyme disease usually causes headache, fever, joint pain. But, if left untreated, it can lead to facial paralysis, palpitations, neurological disorders... It is very common for people who go to areas such as US natural parks to become infected, as they report hundreds of cases every year.
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Finally we have one of the most feared diseases: Ebola. According to the WHO, its fatality rate can exceed 50% on a recurring basis. Due to its characteristics, it is only spread when there are symptoms and the outbreaks have been controlled and have hardly left Africa. But...
But in a world that is so globalized, Ebola has traveled to different parts of the globe, such as the United Kingdom, Spain, Italy or the United States. Only one patient died in the United States. The medicine of developed countries makes a huge difference in terms of lethality.
Scientists warn about the dangers of zoonoses and new diseases. Markets with live animals, deforestation, the irruption of human beings in wild territories; those are all risk factors. And of course, bats, who are the perfect reservoirs for microorganisms that can kill us. Restoring a balance between humanity and nature is necessary to avoid new global health threats.
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