Scientists are finding surprising results in studies they have carried out into monkeypox. Separate studies have looked at people who have been infected with the virus in the past and compared it with sufferers today.
In one, published by Nature Medicine, it warned that the virus behind the current global outbreak may have undergone "accelerated evolution". This means it is mutating much more quickly than scientists would have expected it to.
In a second, separate, study published by The Lancet it told how those found to have the virus were displaying different symptoms to previous outbreaks. It warned it could mean cases are being missed.
The findings comes as the confirmed number of cases in the UK reached 1,351. These have increased by more than 100 over a four day period.
According the the Nature Medicine publication researchers in Portugal discovered the virus was mutating at up to six to 12 times the speed that would normally be expected. This has led them to question whether it is more infectious than it was previously. Those behind the study say as yet it is not known if this is the case.
However what is beginning to emerge is that the symptoms are different than in the past. Teams from Chelsea & Westminster Hospital NHS Foundation Trust, Imperial College Healthcare NHS Trust, Central London Community Healthcare NHS Trust and Imperial College London carried out the first UK study into the ongoing outbreak of the virus.
They looked at 54 patients with confirmed monkeypox infection who attended sexual health clinics in London. The teams discovered key information about those most likely to develop it but also what symptoms they had.
In the study published in The Lancet the researchers reported how they found how current sufferers were less likely to have a fever or be tired however they were more likely to have skin lesions in their anus or genital regions. This suggests it is being transmitted during close skin-to-skin contact such as sexual activity.
The team has called for additional resources to support sexual health and other specialist services in managing the current monkeypox outbreak.
The 54 patients represented 60% of the cases reported in the UK during the 12 day study period during May 2022. All except two of the patients were not aware of having been in contact with a known case and none reported travel to sub-Saharan Africa, however many had recently visited other European countries.
All patients identified as men who have sex with men and there was a median age of 41. Nine out of 10 of the patients who responded to the questions on sexual activity (47/52) reported at least one new sexual partner during the three weeks prior to symptoms, and almost all (49/52) reported inconsistent condom use in this same time period. Over half of the patients (29/52) had more than five sexual partners in the 12 weeks prior to their monkeypox diagnosis.
The patients were all symptomatic and presented with skin lesions; 94% (49/52) of patients had at least one skin lesion on the genital or perianal skin. Mostly the patients had a mild illness and recovered whilst isolating at home, but five individuals required hospital admission due to pain or infection of the skin lesions. All improved and were later discharged.
One in four of the patients tested positive for gonorrhoea or chlamydia at the same time as the monkeypox infection, which suggests that transmission of the monkeypox virus in this group of patients is occurring from close skin-to-skin, for example in the context of sexual activity, according to Dr Ruth Byrne, from the Chelsea & Westminster Hospital NHS Foundation Trust.
She said this might be biased by the fact they were sexual health providers so it might not reflect transmission in the wider population. However she added: “It is possible that at various stages of the infection monkeypox may mimic common STIs, such as herpes and syphilis, in its presentation.
"It’s important that sexual health clinicians and patients are aware of the symptoms of monkeypox as misdiagnosis of the infection may prevent the opportunity for appropriate intervention and prevention of onward transmission. Additional resources are urgently required to support services in managing this condition.”
The study also observed important differences in the clinical features of this group of patient compared to previous cases reported from earlier outbreaks in other countries. A lower proportion reported feeling weak and tired and/or having a fever than in studies on cases in previous outbreaks. Additionally, 18% (10/54) of patients in this cohort did not report any early symptoms before the onset of skin lesions.
Dr Nicolo Girometti, from the Chelsea & Westminster Hospital NHS Foundation Trust, said: “Given the suggested route of infection via contact during sexual activity and the number of clinical findings differing from previous descriptions, we suggest that case definitions currently detailing symptoms such as acute illness with fever should be reviewed to best adapt to the current findings, as at least one in six of this cohort would have not met the current ‘probable case’ definition.”
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