Prolonged detection of monkeypox virus DNA in nasopharyngeal swabs, urine and blood samples

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Up to 11 July 2022, more than 9,000 cases of monkeypox (MPX) have been confirmed in 57 countries [1].

The analysis of seven cases diagnosed in the United Kingdom between 2018 and 2021 revealed prolonged detection of MPX virus DNA in nasopharyngeal swabs, urine and blood samples [2]. In addition, a report of four cases in Italy from the current outbreak detected MPX DNA in semen, faeces and saliva [3].

We aimed to characterise viral shedding to better understand the possible role of different bodily fluids in disease transmission and investigated the presence of MPX virus DNA in saliva, rectal swab, nasopharyngeal swab, semen, urine and faecal samples, from 12 MPX patients in Barcelona, Spain.

The study findings were published in the peer reviewed journal: Eurosurveillance. https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2022.27.28.2200503

The MPX virus is a zoonotic pathogen and the most frequent orthopox virus infection in humans. Since the description of the disease in 1970 in Democratic Republic of Congo, a number of cases have been reported in endemic countries but also outside endemic areas in travellers returning from western and central Africa [2,7]. In 2003, a MPX outbreak in the United States linked to the importation of infected animals was reported [8].

The virus was then considered as an emerging infection and a potential public health threat, which unfortunately has been confirmed in subsequent MPX outbreaks [7], including the current ongoing outbreak [9].

In this study, we provide data on 147 clinical samples, collected at 23 time points from 12 confirmed MPX cases in Barcelona. Our knowledge on MPX virus shedding is clearly limited, but greatly needed in the current epidemiological situation, where many countries are experiencing an upsurge of cases.

To our knowledge, a single report [3] has been published on this issue, reporting results on 24 samples from four cases and detected MPX DNA in semen (three patients), blood (one patient), nasopharyngeal swab (three patients), faeces (two patients) and saliva (one patient). In addition, a study from Germany [10] detected MPX virus in blood and semen of two cases.

In the current outbreak, several clinical and epidemiological data support that close contact often in the context of sexual activity is driving disease transmission [11]. Thus, a detailed description of the presence of the virus in bodily fluids may shed light on the mechanisms of viral transmission.

At the time of diagnosis, MPX virus DNA was detected in swabs of skin lesions in all patients. High viral loads (Cq value range: 16–21) were observed in skin pustules. Some patients presented with additional oral, pharyngeal and rectal lesions. The ability of MPX virus infection to cause proctitis and other atypical clinical presentations warrants further research [12,13]. Interestingly, the analysis of follow-up samples showed shedding of MPX virus in a range of bodily fluids during the first 2 weeks of the illness and up to 16 days after symptom onset.

Our results on saliva samples are of special interest. In a previous report, saliva was only tested once in a single patient [3]. Here, we find that MPX DNA was detected in saliva at some point in all 12 patients studied, in the samples collected between 4–16 days after the onset of symptoms.

The other clinical samples analysed, including semen, frequently contained MPX virus DNA. We did not perform cell culture, and a clear correlation between real-time PCR and virus isolation has not been reported in existing literature. However, results from studies in animal samples that quantified MPX virus and performed cell culture indicate that virus isolation can be successful with viral loads in the range of 104–105 copies/ml [14].

Furthermore, during the present outbreak, MPX virus has been isolated from skin lesion samples with a Cq of 20 in one case [10]. With the low Cq values observed in our study in a variety of samples such as saliva, rectal swab, semen, urine and faecal samples, further research on the infectious potential of these bodily fluids and their potential role in disease transmission by close physical contact during sexual activity is warranted.

The initial spread of MPX in Europe seemed to be related to specific mass gathering events in Spain and Belgium [15]. Our data show that, among the 12 cases studied, history of travel to these areas was absent and only some patients reported having had close physical contact with positive MPX cases.

Indeed, while the studied patient size was small, our accumulated experience with approximately 125 diagnosed cases indicates that, in some of our first cases, the history of travel to the aforementioned events was more frequent, while in subsequent cases, a history of sexual contact with someone who attended one of these events or an absence of this epidemiological linkage was more frequent (data not shown). This, together with the rising number of cases worldwide [1], supports the notion of sustained MPX transmission in the community, at least within MSM risk groups in Barcelona.

An increase in MPX cases has been linked to a decline of smallpox vaccinated population in endemic areas such as Nigeria [7]. Vaccination of high-risk household and identified close contacts is being considered as a complementary measure for the control of the current MPX outbreak by some organizations such as the UK Health Security Agency [16].

Of note, in our study, smallpox vaccination was reported in four out of the seven patients in which this information was available. Additional detailed information on the vaccine history from larger case series as well as coupled serological testing should be performed for a better understanding of the protective effect of the smallpox vaccine against the currently circulating MPX virus strain.

 
Monkeypox Updates :in the last few hours show that the total number of global confirmed infections of monkeypox has reached 14,628 with Spain leading with 3299 cases, followed by the United Kingdom with 2,137 cases, USA with 2,108 cases, Germany 2,033 cases, France 912 cases, Netherlands 656 cases and Canada 596 cases.

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