Microorganisms can be very harmful to us, as they cause a number of human and animal diseases. Diseases in humans like common cold, tuberculosis, measles, chicken pox, polio, cholera, typhoid, hepatitis-B, malaria etc. all are caused by microorganisms. Some serious diseases like- Anthrax is a dangerous human and cattle disease caused by a bacterium. Microbes grow on food products and render them unfit for consumption. Consumption of such food causes food poisoning. Microbes also spoil clothes and leather products. Microorganisms cause diseases of plants like - blights in potatoes, sugarcanes, oranges then, rust of wheat citrus, canker etc. They also reduce the crop yield.

Introduction:
Microorganisms, also known as microbes, are tiny living organisms that cannot be seen with the naked eye. While some microbes are harmless or even beneficial to humans, there are several microorganisms that can cause significant harm. These harmful microorganisms can lead to various diseases and infections, affecting the health and well-being of individuals.

Diseases and Infections:
- Microorganisms such as bacteria, viruses, fungi, and parasites can cause a wide range of diseases and infections in humans. These include respiratory infections like pneumonia and tuberculosis, gastrointestinal infections like food poisoning and diarrheal diseases, sexually transmitted infections like HIV/AIDS and syphilis, and skin infections like impetigo and ringworm.
- Some microorganisms can also cause more severe and life-threatening diseases, such as Ebola, Zika virus, and severe acute respiratory syndrome (SARS). These diseases can spread rapidly and have a high mortality rate, posing a significant threat to public health.

Food Contamination:
- Certain microorganisms have the ability to contaminate food and beverages, leading to foodborne illnesses. Bacteria like Salmonella, Escherichia coli (E. coli), and Campylobacter, as well as viruses like norovirus and hepatitis A, can cause food poisoning and gastrointestinal infections when consumed.
- Improper handling, storage, or preparation of food can facilitate the growth and spread of these harmful microorganisms. Contaminated food can lead to nausea, vomiting, diarrhea, abdominal pain, and in severe cases, organ failure and death.

Antibiotic Resistance:
- Overuse and misuse of antibiotics have contributed to the development of antibiotic-resistant microorganisms. This means that certain bacteria and other microbes have become resistant to the drugs designed to kill them, making infections caused by these resistant strains more difficult to treat.
- Antibiotic resistance poses a significant threat to global health, as it limits the effectiveness of antibiotics in treating infections. This can result in prolonged illnesses, increased healthcare costs, and higher mortality rates.

Environmental Impact:
- Microorganisms can also have harmful effects on the environment. For example, certain bacteria and algae can cause water pollution and harmful algal blooms, leading to the depletion of oxygen levels in water bodies and the death of aquatic organisms.
- Additionally, some microorganisms can contribute to the deterioration of materials and structures, causing damage to buildings, infrastructure, and cultural heritage sites.

Conclusion:
While microorganisms play important roles in various ecological processes and can be beneficial to humans in many ways, it is crucial to recognize and address the harms caused by certain microbes. Effective measures such as proper hygiene practices, vaccination, food safety regulations, and responsible use of antibiotics can help mitigate the negative impact of harmful microorganisms on human health and the environment.

Microorganisms are harmfull in many ways. some microorganisms causes disease in plant and animal are human beings, some insects and animals act As a carrier of disease causing microbes like housefly and mosquito.