August 3, 2022
Human Monkeypox: An Observational Retrospective Study From the United KingdomBy Lauren Richey, MD, MPH, FIDSA
Human monkeypox is a zoonosis that is caused by the monkeypox virus, which is a close relative to the variola virus (smallpox). Initially found in central Africa, it has generally affected the poor and marginalized. It is characterized clinically by a rash, fever, and lymphadenopathy. The case fatality rate varies. This small case series from the U.K. represents imported, nosocomial, and household transmission as well as the use of smallpox antivirals in humans to treat monkeypox.
The observational retrospective series included all patients with confirmed monkeypox admitted to the High Consequence Infectious Disease Centre from August 2018 to September 2021. A confirmed case was defined as a compatible illness and a positive monkeypox PCR. There was a total of 7 cases. There are no licensed treatments for monkeypox, but two agents approved for smallpox were available (brincidofovir and tecovirimat) and were used in this series.
Four of the patients acquired monkeypox outside of the U.K., and one was nosocomial acquisition. The health care worker described became ill 18 days after exposure to a patient without PPE, despite receiving a smallpox vaccination on day 6 after exposure. All patients had pleomorphic skin lesions, including vesicles, pustules, papules, and/or ulcerations that were positive for monkeypox. All had positive viral DNA in respiratory tract swabs, 6 in their blood, and 4 in their urine. Five spent more than 3 weeks in isolation due to continued PCR positivity. Three patients were treated with brincidofovir, and all had alanine transaminase elevations and did not complete the course. No association with clinical or virologic parameters was seen with its use. One patient was treated with tecovirimat. This patient had a negative PCR of the blood and upper respiratory tract 48 hours after starting the medicine and no new lesions 24 hours after starting the therapy. Liver, renal, and hematologic labs remained normal. None of the patients had preexisting medical problems, and all fully recovered.
Clearly limited by a small sample size, this study does provide some insight into the long duration of PCR positivity, although the absence of viral culture prevents confirmation of continued shedding of viable virus. It is also the first publication of the use of these smallpox medications in humans to treat monkeypox.
