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Monkeypox is a rare disease, first discovered in monkeys in 1958.  The first known human case was identified in 1970. U.S. monkeypox cases are very rare. Monkeypox can be found in animals (African rodents, monkeys, and other primates) and usually encountered in villages in west and central Africa. Persons in Illinois could become infected by traveling to west and central Africa and being exposed to people or animals with the disease.  One human outbreak in the U.S. in 2003 occurred when African rodents came in contact with pet prairie dogs at an Illinois animal vendor.  Some persons in contact with the infected prairie dogs developed monkeypox, including 10 Illinois residents. 


Monkeypox can be transmitted by exposure to respiratory droplets and by contact with infected skin lesions or contaminated materials.

Recent Developments

In 2022, there have been monkeypox outbreaks in Europe and one reported case in Massachusetts where the infected individual had not traveled to Africa.  Some of the outbreaks have patients who identify as gay, bisexual, or other men who have sex with men. These outbreaks are currently under investigation and more information is expected in the future. Therefore, health care providers in Illinois should be alert for any suspect cases, even if the patient has not traveled but has an illness suspected to be monkeypox. These cases should be promptly reported to their local health department. Requests for testing should be made through the local health department.

Disease characteristics

Monkeypox is in the orthopox virus family, which includes cowpox and smallpox. Smallpox is no longer circulating in the world and was declared eradicated by the World Health Organization in 1980. Symptoms of monkeypox are milder than the symptoms of smallpox. The main difference between smallpox and monkeypox is that monkeypox causes lymph nodes to swell while smallpox does not. The incubation period for monkeypox is usually 7-14 days but can range from 5-21 days. 

Monkeypox illness begins with:

  • Fever
  • Headache
  • Muscle aches
  • Backache
  • Swollen lymph nodes
  • Chills
  • Exhaustion

Within 1 to 3 days (sometimes longer) after the appearance of fever, the patient develops a rash, often beginning on the face and then spreading to other parts of the body.

The illness typically lasts for 2-4 weeks.

Prevention and control measures 

There are a number of measures that can be taken to prevent infection with monkeypox virus:

  • Avoid contact with animals that could harbor the virus in countries with monkeypox, such as central and west Africa (including rodents, marsupials and non-human primates and animals that are sick or that have been found dead in areas where monkeypox occurs).
  • Avoid eating wild game meat (bush meat) from countries where monkeypox is present in animals.
  • Avoid contact with any materials, such as bedding, that has been in contact with a sick animal.
  • Isolate infected patients from others who could be at risk for infection.
  • Practice good hand hygiene after contact with infected animals or humans. For example, washing your hands with soap and water or using an alcohol-based hand sanitizer.
  • Use standard, contact and droplet infection control precautions in the health care setting when caring for patients.
  • Contact tracing is needed with each case of monkeypox to identify others who may become infected.
  • Persons who have had contact with a suspect or confirmed animal or human case should be quarantined and followed up for 21 days after their last exposure.
  • Historically, smallpox vaccine can provide protections against monkeypox. These vaccines are not widely available. A smallpox vaccine can be used in persons who have had contact with an infected monkeypox case but approval for the vaccination must be obtained from public health authorities.

For more information regarding monkeypox, visit the CDC website or the World Health Organization.