Fenómeno que consiste na combustão de grandes áreas florestais e conduz à libertação de grandes quantidades de CO2 para a atmosfera.

Wildfires.

Explanation:

Wildfires is the phenomenon that causes combustion of large forest areas and leads to the release of large amounts of CO2 into the atmosphere. Wildfire occurs naturally as well as carelessness of humans that leads to the destruction of large area of forest and the habitat of wild animals also destroyed which compels them to migrate from that region. This wildfires produced high amount of carbondioxide gas in the atmosphere that is the main cause of air pollution.

Infection is a general term referred to the invasion of foreign microorganisms into our body. These foreign microorganisms include bacteria, viruses, parasites and pathogens. They should come from outside the body to be considered as an infection. Symptoms may or may not effect from it. 

The answer is microorganisms colonizing the body.