Causes for Emerging Infectious Disease: Humans are to blame.
By: Dr. Eeks
We must address the causes of emerging infectious disease. For example, there has to be a much stronger international effort to ban live meat markets and come down harder on the illegal wildlife trade. It didn’t happen after SARS, but it needs to happen now. Turning a blind eye to them is the equivalent of playing an international game of Russian Roulette. Both are long known to be significant factors that contribute to emerging infectious diseases, and if they continue, we will certainly have another Disease X. And we’ll have another one after that, and another one after that…, and one of those Disease Xs will be far more lethal than COVID-19.
Outbreaks might have been kept more localized before rampant air travel and high-speed railway, but they aren’t anymore. Take Wuhan, for example. COVID-19 is potentially linked to originating from the Huanan South China Seafood Market- a live animal market. Genomic sequencing showed that COVID-19 was 96% identical to a bat coronavirus, meaning the bat was most likely the original host. COVID-19 is a zoonotic infection, meaning it doesn’t cause disease in bats, but it does when it jumps species, for example to the human species. How does a virus jump to the human species? When humans come in close contact with bats. Some research also suggests that minks and snakes were intermediate hosts for COVID-19. Either way, bats, minks and snakes were all sold at the market.
Wuhan is a city of 11 million with a high-speed railway system & airline flights connecting it to other cities in China, but it’s also connected internationally via direct and indirect flights. According to transportation data I saw, in one month ( January), there were close to 700,000 passenger bookings from Wuhan. Given a virus like COVID-19, one that has a long serial interval time (time between appearance of symptoms in the index case to appearance in secondary case) and a long incubation period (5-6 days, maybe longer) leads to a high level of asymptomatic spread. A high level of asymptomatic spread plus a high level of both domestic and international travel can lead to an international public health and economic disaster.
We will get through this pandemic and reach a much more optimal equilibrium with COVID-19: One where we are ahead of the virus and not playing catch-up; one where the viral reproductive number shifts closer to 1; one where the viral doubling time will lengthen (which will significantly slow down its exponential growth), and one where the susceptible population will decrease. The best treatment drugs will be determined via randomized controlled trials and a vaccine will be developed. However, a lot of lives will be lost in the process. Some might be our friends and family members. That’s a permanent and devastating loss, and there’s no coming back. The economy will be damaged, but at least that has the opportunity to bounce back. My one hope is that when this new, relatively-normal equilibrium is reached, and when we’re back to socializing, shopping, living a care-free, mask-free life with an abundance of ventilators, toilet paper and hand sanitizer, we won’t forget about the causes of emerging infectious diseases, like COVID-19.
I’ve mentioned two driving factors, live meat markets and the illegal wildlife trade, that are specific to the spread of COVID-19. There are many other driving factors, all well-researched and documented, and all having to do with how humans interact with the environment and its various species. These include: antibiotic resistance due to overuse in farm animals or over-prescription; eating bush meat or raw meat; land misuse; deforestation; building pools of standing waters, such as dams and irrigation systems ( mosquito-borne illnesses); unsafe sexual practices; burial practices (Ebola outbreak); ineffective or lack of vaccination; war; famine; migration; certain agricultural practices and more. One can classify historical outbreaks by the driving factors, which is one of the things I did during my Public Health research internship.
Lately, coronaviruses in bats (the reservoir) have been implicated in serious respiratory diseases in humans. Bats aren’t the problem. In fact, bats are essential. They pollinate fruit trees and control the insect population. They are an excellent organic public health intervention for controlling mosquito-borne illnesses, like malaria and Dengue fever. Bats are great, as long as we don’t come too close. Unfortunately, human ignorance is forcing an unprecedented closeness. Let’s use Southeast Asia as an example. Over the last 40 years, Southeast Asia has experienced a huge amount of deforestation, losing between 30-40% of its forests. This is due to expanding agriculture and land development. Though deforestation cuts into the “bats’ land,” bats are incredibly adaptable creatures. They can adapt to a more agrarian and developed environment ( a house can make a great bat cave), but this increases our chance of close contact: through direct means; through domesticated and farm animals; or through bat urine and feces. That means a bat coronavirus can more easily jump from a bat to one of our domesticated or farm animals, or it can jump to us directly. It’s suggested that the Middle Eastern Respiratory Outbreak (MERS) started this way. MERS-CoV may have first jumped from fruit bats to dromedary camels, and then to humans who came in contact with infected camels.
So, don’t forget. When we emerge on the other side of COVID-19, don’t forget about the causes for emerging infectious diseases. It’s that simple. Prepare for outbreaks, always. But if we don’t address the factors leading to emerging infectious diseases, we will have many more Disease Xs.
Thanks for reading!
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