Monkeypox outbreak in Nigeria

In the latest in a series of Tropical Diseases, Travel Medicine and Vaccines blogs highlighting the current hot topics in tropical medicine, Dr. S. Chakrabarti, Dr. S. Clarke, and Dr. A. Boggild discuss the moneypox virus and its outbreak history in humans from 1970 to present day.

Monkeypox (MPX) is caused by the monkeypox virus (MPXV), related to both smallpox and cowpox. The first recorded case in a human occurred in 1970 in the Democratic Republic of Congo (DRC). It is currently endemic to regions of the Congo Basin and Western Africa— but largely the DRC.

Symptoms are similar to, but sometimes less severe than, smallpox. It is generally transmitted from animal to human (through contact with infected bodily fluids as well as improperly cooked meats), however human-to-human transmission has been documented as well.

There is no known treatment that is considered safe or effective; however, the smallpox vaccination has been shown to be protective against the development of monkeypox in retrospective studies. There have been a series of small outbreaks outside of the DRC in the past two decades.

US outbreak 2003

Prairie dog

In 2003, monkeypox was introduced to the US with an exotic pet import— predominantly rodents such as mice, squirrels, and rats— from Ghana to Texas, some of which were infected with the virus. Following the import, the animals were distributed to an animal vendor facility in Illinois. In this facility, some of the infected rodents’ cages were adjacent to the prairie dogs’ cages. This is suspected to have been the cause of transmission and subsequent distribution of the disease across the US— including some transmissions to humans. The smallpox vaccine was offered as part of the outbreak control to minimize transmission.

Nigerian outbreak 2017–2018

The first confirmed cases in Nigeria occurred in September 2017 in the state of Bayelsa. At this time, there were 33 suspected cases in 7 states with a majority of the cases occurring in persons over the age of 20. The disease spread widely throughout the country. By 2018, there were 45 confirmed cases and 114 suspected cases of monkeypox including one death (in an individual with advanced, untreated HIV). Co-ordination by the Nigeria Centre for Disease Control contained the disease and suspected and confirmed cases were managed at designated facilities.

Imported cases

Imported cases have been reported in the UK and Israel. In Israel, the only reported case was an Israeli man who lived and worked in Port Harcourt located in Southern Nigeria.

In the UK, there have been three cases, including one of human-to-human transmission. The first of the three cases related to a Nigerian Naval Officer, who was in Cornwall on a training exercise, and the second case was a man who had returned from travel to Southern Nigeria.

The third case was of particular interest in the UK national press, as it was the nurse who had treated patient number two in Blackpool, England. Although the d

eputy director of Public Health England’s National Infection Service said that it was not surprising a case had been identified, monkeypox was not initially suspected and therefore full personal protection equipment was not worn to prevent infection. Smallpox vaccinations were administered for prevention of further human-to-human transmission.

This outbreak was widely reported in the UK as it successfully tested the NHS’ ability to respond to outbreaks of tropical diseases with a contingency plan that had been designed by health officials following the Ebola crisis of 2014.

The outbreak continues in 2019, with over 300 cases reported to date in Nigeria. In May 2019, a fourth exported case from Nigeria was reported by the Singapore Ministry of Health, and as of May 15th, 14 close contacts of the affected individual had received preventative smallpox vaccination. Monitoring and surveillance continues in Singapore, and travelers to Nigeria should practice usual precautions such as frequent hand-washing and avoidance of animal contact.

Child receiving vaccine


Monkeypox is still relatively rare and largely zoonotic. It is transmitted through contact/respiratory droplets, with the primary suspected reservoir being rodents. The smallpox vaccine is being used for prevention as it is theorized to have cross-protection benefits. Currently, there is an outbreak in Nigeria that is being investigated and infection control is being implemented. Monkeypox should be considered as part of the differential diagnosis in individuals presenting with widespread vesicles/pustules with a history of travel to Nigeria or West/Central Africa or who may have had potential exposure to exotic rodents or prairie dogs.

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