Corona virus origin and spread

 

                      

    

                               Where did the virus behind COVID-19 come from? It's a question that's dogged researchers since the early days of the pandemic. Most maintain it jumped from bats to humans in a Chinese market. Some claim it could have other origins – in particular, a breakout from a lab working with viruses.

Getting answers hasn't been easy. China has been guarded. And scientists warn that the window to finding COVID's true origin is closing fast. The debate that has turned highly-political, at times threatening to overshadow management of the pandemic itself. Solving the puzzle is still critical. Determining the origin of Sars-Cov-2 could help outbreaks of new diseases, and stop future pandemics before they start. A new US-intelligence report also fails to settle on an origin theory. But it does give a small peek into the ongoing debate. An unclassified summary of that report says outright that it's unlikely the virus was developed as a biological weapon, or that Chinese officials even knew about the virus. Most intelligence agencies in the US still think it was a transmission that occurred outside of the lab. But the report doesn't dismiss the lab-accident theory, saying one agency concluded that account was more probable, while two other agencies said they couldn't reject the idea. The report said more evidence is needed, in particular early clinical samples of the virus. That appears unlikely to happen, and it means the debate over origin will continue.

Pathogens that cause disease in people and other animals — called zoonotic diseases — aren’t uncommon: Rabies, flu viruses and HIV, the virus that causes AIDS, are all familiar examples. But the threat of such pathogens is growing. Researchers who monitor for emerging infectious diseases typically recognized about three per year, says epidemiologist and disease ecologist Jonna Mazet. In the last decade that’s increased to about five per year. That uptick is not the fault of the animals that carry these pathogens, says Mazet, of the University of California, Davis. “It’s our human behavior and the risky things that we do that put ourselves at risk for exposure to these viruses.” Mazet details some of the factors that increase that risk, which include changes in how and where people interact with wildlife. As people push further and further into places that were previously uninhabited — such as mining for materials that make our cell phones lighter — the probability of encountering unfamiliar viruses increases. “We are exposing ourselves to things that just aren’t in our evolutionary history and we’re really at risk,” Mazet says. The virus behind the pandemic, SARS CoV-2, was one such “jumper.” Evidence suggests that its original evolutionary host was a horseshoe bat, one of many viruses that bats appear to tolerate with little to no ill effects. And there will likely be more such “spillover” events to come. “We know that in the viral families that are known to cause human disease and be shared with other animals, that there are at least 500,000 viruses still to discover that can infect us and could make us sick,” Mazet says. “We've only scratched the surface.” Ultimately, we have to rethink how we interact with the environment, Mazet says. “We’re talking about the interconnected health of the whole planet — the people, the animals, the environment — and when we do protect that we protect ourselves for the longer term.”