Ulcer at the corner of the mouth has now been documented by scientists as the first sign of infection with the monkeypox virus.

Recent infection with the monkeypox virus can initially present with very few pronounced clinical symptoms and lacking signs of infection, and only a few skin vesicles may be visible.

German researchers have now presented the case of a 51-year-old HIV-positive patient, whose ulcer at the corner of his mouth occurred as the first sign of infection with the monkeypox virus.

According to Stefan Schlabe, University Hospital of Bonn, Department of Medicine, and colleagues, the patient presented to his general practitioner with a vesicle at the left corner of the mouth that had appeared the day before.

"He had no clinical signs of infection; his HIV infection had been well controlled for years, both virologically and immunologically, with antiretroviral therapy," said the study published in the journal Deutsches Arzteblatt international.

Initially, the patient's ulcer was treated with a topical combination ointment. Within a few days, he developed a painful ulcer at the left corner of his mouth and went back to his general practitioner. A swab was taken from the ulcer.

"Testing by polymerase chain reaction (PCR) confirmed monkeypox virus. Subsequently, an increase in monkeypox vesicles was noted on the skin, but also on the palate," the researchers noted.

With growing swelling of the base of the tongue and muffled speech, it was decided to admit the patient to the hospital for antiviral treatment with tecovirimat, they added.

The monkeypox outbreak continues to be a global health emergency, which is the highest level of alert as per the World Health Organisation (WHO). There have been nearly 80,000 cases so far recorded across 106 countries, with 36 deaths.