Monkeypox is a disease caused by a virus that is mainly transmitted to humans from animals. Diseases that are transferred from animals to humans are called zoonotic diseases (or zoonosis). As a result, monkeypox is classified as a viral, zoonotic disease. 

Transmission from animal to human happens when a human comes into contact with the blood, bodily fluids or skin of an infected animal. This could happen either by directly coming into contact with an infected wild animal, or indirectly if a domesticated animal is infected by a wild animal before coming into contact with a human. Another possible method of transmission could be humans unknowingly eating meat of infected animals that was not properly cooked. 

Transmission between humans can happen in several different ways: - Contact with respiratory fluids (similar to transmission of the flu or COVID-19) - Contact with infected skin - Contact with objects that have been recently contaminated by the virus.  - Contact between mother to baby during or after birth, or through the placenta during pregnancy.

Another possible mode of transmission could be sexual transmission (meaning transmitted during vaginal, anal, or oral sex througu bodily fluids). Research has not confirmed this yet, however, because the virus can spread through skin-to-skin contact and respiratory fluids, one could be infected through acts of physical intimacy.

Infected humans usually do not show symptoms for about 6 to 13 days, and in some rare cases up to 21 days. This period between infection and symptoms is called the incubation period. Importantly, a person who is infected with monkeypox is not contagious during the incubation period, unlike COVID-19. 

Symptoms initially include fever, intense headaches, back and general muscle pains, and swelling of the lymph nodes. Swelling of the lymph nodes (also called lymphadenopathy) is the most distinctive symptom of this disease. Skin rash typically appears between 1 and 3 days after a fever starts as red bumps on the skin. It starts on the face and then spreads to other parts of the body such as the palms of the hands and the soles of the feet and can also affect the inside of the mouth, genitals, and eyes.

In most cases, symptoms of monkeypox resolve on their own, and the body can clear the infection in 2 to 4 weeks. Severe cases can occur, and are most commonly seen in children and people with reduced immunity because of an existing condition (like HIV/AIDS or those on chemotherapy). 

The virus was first identified in 1958 in macaques being used for research in Denmark. It is part of the same family of viruses as smallpox. This family is called poxvirus, and both of these viruses have somewhat similar symptoms to each other, including pox-like lesions on the skin. Monkeypox tends to cause less severe symptoms than smallpox. However, despite the eradication of smallpox in 1980 due to the use of the smallpox vaccination, monkeypox continues to appear, primarily in Central and West Africa.

Monkeypox can infect some types of animals, including types of squirrels, rats, and primates other than humans (like monkeys). However at the moment we do not know enough about how the virus moves in nature between animals. 

Public Health professionals are concerned due to the recent appearance of monkeypox in non-endemic countries, without finding a clear travel history to connect it to countries in Central and West Africa. This may suggest the virus has been spreading silently, which could mean the extent of the spread is more than what is currently seen. While scientists are always concerned with any new behavior of any virus, they are not panicked about the spread of monkeypox as this is a disease that we already have treatments for and for which we have vaccines available.