What is one way that micro organisms can be harmful to humans?

Microbes cause infectious diseases such as flu and measles.

https://microbiologyonline.org/about-microbiology/microbes-and-the-human-body/microbes-and-disease

Microorganisms include bacteria, algae, fungi, archaea, viruses, and protozoa. They are very small but they can cause diseases and even lead to death. Some of them are free-living but some are parasites.

type 2 happens when excess consumption of high-sugar foods flood the blood supply with glucose and reduce the production and effectiveness of insulin. if a person has prediabetes, they can reduce the risk of full diabetes through regular exercise and a balanced, low-sugar diet.