Figure

Figure. Lesions on patient who had clade Ib monkeypox virus infection linked to travel to the Democratic Republic of the Congo, Thailand, 2024. A, B) Necrotic papules with overlying scabs on...

A 66-year-old man of German nationality who resides in eastern Thailand traveled to Germany on June 18, 2024. On July 30, he departed for Rwanda and then traveled to Bukavu, South Kivu, DRC, on August 1. He stayed with 2 friends in an apartment and denied participating in any sexual activity or having contact with infected persons during his visit. His friends reported no abnormal symptoms. He reported that he rarely wore a mask or washed his hands with soap or sanitizer during his stay. On August 10, genital itching developed. On August 13, his co-worker drove him to the border, and he took a taxi to the airport in Rwanda, where he departed and transited through Qatar, arriving in Thailand on August 14. On that same day, his symptoms progressed to fever, muscle aches, sore throat, fatigue, and rash, which primarily affected his genitalia, trunk, extremities, and face. His wife picked him up from Suvarnabhumi Airport (Thailand); they had dinner together in Bangkok before checking into a hotel. On August 15, he visited a private hospital and was admitted. On examination, he had multiple discrete erythematous maculopapular lesions and a few vesicular lesions distributed across his face, trunk, and extremities and had some necrotic papules with overlying scabs on his penis and right thigh (Figure).

We collected clinical samples on August 16, 21, and 29 and September 2. A private laboratory conducted real-time PCR and detected MPXV in the samples by amplifying the F3L gene; however, the result for clade I MPXV D14L gene amplification was inconclusive. The Thai Red Cross Emerging Infectious Disease Clinical Center also detected MPXV but did not specify the clade. We sent a swab sample from August 21 to the Bamrasnaradura Infectious Disease Institute, where clade II MPXV was identified by using the QIAstat-Dx Viral Vesicular Panel (QIAGEN, https://www.qiagen.com). Because of conflicting results, we sent a swab sample from August 16 to Thailand’s national reference laboratory at the National Institute of Health (NIH) for confirmation by whole-genome sequencing. The Thailand NIH confirmed the sample was clade Ib MPXV and deposited the sequence in the GISAID database (https://www.gisaid.org; accession no. EPI_ISL_19350788).

The lowest cycle threshold (Ct) value of 13.73 was obtained from a sample of combined vesicles and pustules collected from the patient’s genitalia 6 days after symptom onset. The patient began treatment with tecovirimat on August 20. A subsequent swab sample from a scab lesion on the left leg showed the highest PCR Ct value 23 days after symptom onset (Ct 38.48). Cultures from all swab samples tested at NIH showed no virus growth (Table 1). The patient was discharged on September 5 without complications.

Contact tracing identified 89 persons who had direct contact with the patient’s skin, bodily fluids, or contaminated objects (fomites) or who were within 1 meter of the patient during potential aerosol-generating activities. Among those 89 contacts, 33 were classified as high-risk because of exposure without proper personal protective equipment: the patient’s wife, 13 flight passengers, 12 healthcare personnel, 6 hotel staff, and 2 restaurant staff (Table 2). Symptoms did not develop in any high-risk contacts during the monitoring period; no secondary cases were observed. Because of the close contact, a regional public health officer collected nasopharyngeal swab samples from the patient’s wife on days 7, 14, and 23 after her last exposure to the patient. All samples were negative for MPXV by PCR.

Before the WHO public health emergency declaration, Thailand did not have specific mpox screening measures at points of entry. Mpox cases could potentially be identified through existing yellow fever screening by the Port and Quarantine Office, which focuses on travelers from 42 yellow fever–risk countries (5). Screening procedures conducted by public health officers include taking travel history, checking body temperature, and verifying the International Certificate of Vaccination for yellow fever and Thailand Health Pass registration. At the time of the WHO declaration, 5 ongoing mpox outbreaks in DRC, Burundi, Kenya, Cote d’Ivoire, and Uganda overlapped with the yellow fever list. However, Rwanda was not among those. Nonetheless, on the day of arrival in Thailand, the patient voluntarily walked to the screening area wearing a long-sleeved shirt and hat and did not report any illness. Thus, the officer did not observe any visible rashes on his face.

At hotel R, public health officers from the Health Department of the Bangkok Metropolitan Administration collected environmental samples from suspected contact surfaces in the hotel room 9 days after the patient had checked (Table 3). All samples tested positive for MPXV except those taken from the light switch and the doorknobs of the bedroom and living room. The positive samples had Ct values ranging from 28 to 38; the lowest Ct value was detected on the curtain knob (Table 3). The hotel staff used 3 types of cleaning products containing active ingredients, such as citric acid, alkyl alcohol ethoxylate, didecyldimethylammonium chloride, alkyldimethylbenzylammonium chloride, and ethanol. At restaurant A, ethyl alcohol spray was used for table cleaning. All of those chemicals are considered effective against MPXV (6).

We report a travel-associated case of imported clade Ib mpox infection in Thailand with a mild clinical course, consistent with other clade Ib mpox infections reported outside of Africa (7). The likely source of infection was human-to-human transmission during community activities in DRC, differing from reports of predominantly sexual transmission among adults in the country (8,9). Inconsistent PCR results were attributed to the use of different detection methods across laboratory centers. Clade Ib MPXV contains a large deletion of ≈1,000 nt in the D14L gene region (8,9), which was the target sequence used in the private laboratory's real-time PCR and resulted in an inconclusive signal for clade I MPXV. Furthermore, the multiplex PCR kit used by the Bamrasnaradura Infectious Disease Institute exhibited cross-reactivity between MPXV clades I and II, leading to sample misidentification as clade II MPXV. The assay provider (QIAGEN) has since corrected this issue. For more accurate and timely diagnosis of clade Ib mpox, newly developed PCR methods are recommended (10). Swab samples taken from scab lesions still had detectable MPXV by real-time PCR; Ct values ranged from 30.88 to 38.48. Patient isolation duration and the contact monitoring period for clade Ib mpox should align with the US Centers for Disease Control and Prevention’s recommendations (11).

Strengthening Thailand’s public health response is crucial to prevent future travel-associated and imported clade I mpox cases. Point-of-entry screening should include visual inspection of travelers arriving from countries facing ongoing mpox outbreaks to detect rashes on the face and extremities. Healthcare providers should consistently use appropriate personal protective equipment and obtain detailed travel history from patients manifesting clinical symptoms compatible with mpox. In 2024, mpox vaccines were not publicly available in Thailand; thus, preexposure vaccination should be considered, especially for high-risk persons.