SOURCE


MICROBES
The Covid-19 virus is one microbe out of many millions which live in creatures. There are also microbes which protect us from viruses. As a host of all types of microbes, it is important we keep our (personal) microbial communities diverse and balanced (Sommer, 2017). Our resilience towards a virus is partly depending on its ecology.

With a decline of biodiversity of animals, there is an increased risk an entire species is affected. This could make the entire ecosystem weaker and more fragile towards viruses. A vaccination is an example of adding a virus in a controlled way to an ecosystem to increase resilience.

Source: Sommer, The resilience of the intestinal microbiota influences health and disease, Nature Reviews Microbiology volume 15, pages 630–638 (2017)

​ANIMALS
Microbes stay often with a species and most of the time a virus is not harmful for a certain animal. A virus can become harmful when it finds a new host. Viruses like SARS, Covid-19, HIV, Mexican flu and Ebola already existed in animals before they found a human as a new host. 

When animals are put in situations where their body liquids can exchange with other species it can break out and find a new host. Places where people slaughter wild animals are an increased risk for people to get in contact with a new virus. Not only wild animals can be a host of a virus. Also cattle can get infected. High density captivation of animals increases the risk of a virus to spread. Also in Western countries with high hygiene standards in farms, it still happens a new virus spreads itself along its cattle. 

GLOBAL TRAFFIC
The risk of a new virus entering society is very little. But when many groups of people are connected in a global network, the plausibility of a pandemic increases. Another side effect is that air pollution which is mainly contributed by industry and traffic makes people their longs weaker. With Covid-19 a part of people at the intensive care already suffered from long diseases caused by air pollution. A society effected by air pollution might be less resilient to a virus. 

When it comes to trade and intercontinental flights, policy might help to prevent a virus from spreading to other countries.