The Recusant Resurgence of Retroviruses
By Ellen Ziviani Soares
A retrovirus is a family of RNA viruses that inserts its genetic code within a host cell in order to replicate. Retroviruses easily mutate and are not particularly easy to treat with antiretrovirals and stem cell transplants.
A well-known retrovirus is HIV, which can cause AIDS, fevers, pneumonia, and swollen lymph nodes. The best-known treatment is currently antiretroviral drugs (Highly Active Antiretroviral Therapy [HAART] is a very common treatment course, deemed to be the most effective). Antiretroviral drugs work by blocking some stages in the virus's cell cycle so it cannot replicate (either by preventing its genetic material from copying or preventing cytokinesis from taking place). HAART has the ability to make HIV undetectable in tests, although if inconsistent and high enough doses are not taken the virus can mutate and become resistant to the antiretrovirals causing a spike in its detectability as well as becoming increasingly difficult to treat. Currently, two people have been deemed HIV-free (with at least a year buffer period to ensure the virus does not reappear) as a result of HAART, bone marrow transplants (stem cell therapy), chemotherapy, and radiation therapy. There are many pharmaceutical companies working not only on new HIV drugs (including antiretrovirals) but also a ground-breaking vaccine.
The Australian Koala population is also a particularly interesting retrovirus case study. One would think Koalas share very few medical similarities to humans, yet Koalas are also suffering from retrovirus epidemics within their own wild populations. Earlier this year, studies have found that around 50,000 years ago a Koala was infected with a retrovirus (known as KoRV) and this altered the genetic code within their gametes, causing the virus to be transmissible in every cell of each Koala's offspring. KoRV is believed to be the cause of the high frequency of cancer found in the species as its growing cases of insertion into the germline has indicated the virus is active and changes the germline each time it reinserts itself into a new locus, creating new mutations. The accumulation of these mutations may cause unregulated cell division in Koalas and therefore create tumours. Leibniz Institute for Zoo and Wildlife Research (IZW) in Germany noted that the retrovirus was found at increased frequencies in tumour cells as well as creating a cancer-related gene in the genome of one koala they studied.
Although we are making progress globally in terms of HIV, a retrovirus that has been plaguing human life since the 1920s when it was transmitted from chimps to humans, and identifying retroviruses, we cannot simply sigh in relief as new and emerging retroviruses are of concern to the human population once more. It is simply inevitable that there will be another pandemic in the near future. As climates are warming, permafrost and glaciers have been melting at increased rates causing sea levels to rise and threatening coastal developments. These superficial concerns should be the least of our worries as ice cores reveal ancient retroviruses trapped in permafrost and glaciers. The respective ancient retroviruses have defrosted and jolted back to life, posing a real threat to global health as global warming escapes the grasps of being tamed.
These trapped retroviruses have been found on separate occasions around the globe, albeit different viruses which have arguably more disastrous implications. One of the first studied cases of this occurred in 2014 where Siberian scientists found a retrovirus -Mollivirus Sibericum- believed to be over 30,000 years old in permafrost. As permafrost thaws, trapped carbon dioxide and methane are released, generating a greenhouse effect as both compounds are particularly effective at absorbing radiation from the sun and trapping them within Earth's environment. Once defrosted, there is a high chance encountered viruses would return to their normal viral functions. An area of concern is the risk of these newly awakened viruses infect insects, like mosquitoes, which could then act as a vector between animal species and maybe potentially humans. Thankfully, this particular virus is not able to reproduce in humans or animals. That's one more pandemic-sized bullet; dodged.
As expected, we can't celebrate the dodged bullet just yet. Between 2019 and 2021, two more retroviruses have been released from permafrost in Tibet and another in Siberia. The second virus found in Siberia contaminated water and soils in Siberia and transferred the virus from the carcass of a reindeer trapped in permafrost to an estimated 21 people and many reindeer nearby. The outbreak of the virus was especially concerning given the severity of its presence within humans, causing death even in the smallest of outbreaks. The thawing of the permafrost is particularly beneficial for oil companies, allowing reserves to be more easily accessible for extraction and may even cause a boom in mining as soils become easier to remove. In May 2020, the world's largest oil spill from a collapsed Nornickel oil tank took place in Russia, irreversibly damaging the ecosystem of nearby aquatic life. This incident has been suspected by scientists to cause the melting of arctic permafrost, furthering the risk of retroviruses resurgence and epidemics.
Overall, climate change has much greater resultant effects than previously suspected and retroviruses are a very real threat that may cause the mass extinction of the human species before climate changes causes failed crops and poor water supplies. It is almost inevitable that modern-day medicine will not be able to keep up the demand for new antiretrovirals and vaccines as more viruses and even bacterial infections are transmitted between species as a result of poor conditions and antibiotic resistance.
