The Centers for Disease Control (hereafter referred to as CDC) announced that in August 2026, two new locally transmitted cases of monkeypox Clade Ib (hereafter referred to as Ib type) were confirmed, and neither had received a monkeypox vaccine before onset. Both were men in their 30s. The first case sought medical care in late July after developing fever and a red rash with pustules on the abdomen and groin; the physician suspected monkeypox and reported it, leading to a confirmed diagnosis. The second case, in early August, developed a red rash on the trunk and legs, followed by fever and muscle aches; as the rash spread to multiple body parts, the physician suspected monkeypox, performed testing, reported, and confirmed the diagnosis. After genetic typing by the agency, both cases were confirmed to be Ib type, representing the first two domestic cases of monkeypox Ib type in the country.
The CDC noted that, according to international data, both Ib and II types can cause fever, lymphadenopathy, and vesicular skin lesions, but the systemic rash of the Ib type is more widely distributed. Moreover, the Ib type spreads more easily within households than the II type, and individuals with weakened immunity (such as young children, pregnant women, or those with chronic illnesses) are more likely to develop severe reactions. Overall, the symptoms of Ib and II types are similar and their case-fatality rates are comparable; severity is related to the patient’s immune status. The current monkeypox vaccine can effectively prevent Ib infections, and the antiviral drug Tecovirimat is also applicable for severe Ib cases.
The CDC reported that, as of August 23 this year, Taiwan has added 28 confirmed monkeypox cases (19 locally transmitted and 9 imported), all of whom are young adult men aged 20–50. Since monkeypox was classified as a Category 2 notifiable disease in June 2022, a total of 544 cases have been confirmed (500 domestic and 44 imported). This year’s case count is lower than the same periods in 2024 and 2025 (48 and 31 cases, respectively). Epidemiological investigations indicate that most confirmed monkeypox patients have engaged in unsafe sexual practices, and nearly 90% have not been vaccinated against monkeypox. Since the first imported Ib case in May of this year, a total of nine Ib infections have been recorded (seven imported and two domestic).
The CDC explained that the global monkeypox outbreak continues; since 2022, a total of more than 188,000 confirmed monkeypox cases and 521 deaths have been reported across 145 countries/regions, primarily in the Americas and Africa. In recent years, the threat of cross‑border transmission of the Ib variant has increased. Since January 2024, 66 countries or regions have reported confirmed Ib cases. In the past six weeks (June 8 – July 19), the only Asian country reporting cases was Thailand with 29 cases; the majority of other cases were in African nations. Additionally, 16 countries have reported community transmission of the Ib type (five in Africa, ten in Europe, and only Thailand in Southeast Asia). Madagascar has experienced the largest Ib outbreak worldwide since December 2025. Because the Ib virus continues to spread across borders, the risk is assessed as moderate for groups engaging in high‑risk behaviors, especially those without a regular sexual partner, while the general public’s transmission risk is low.
The CDC’s statistics show that by the end of July this year, 110,971 people had received at least one dose of the monkeypox vaccine, of whom 79,216 had completed the two‑dose series, leaving 31,755 people (29%) still needing a second dose. The CDC reminds that the incubation period of monkeypox can be up to 21 days, and some cases can transmit the virus 1–4 days before symptom onset. Vaccination remains the most effective preventive measure, protecting against both the I and II lineages. A total of 318 partner medical institutions nationwide provide publicly funded monkeypox vaccination services. Eligible individuals include those who have engaged in high‑risk behaviors in the past year (e.g., multiple sexual partners, sex work, sexual activity in commercial venues), those with a history of sexually transmitted infections, or those whose sexual partners meet any of the above criteria; they should promptly complete the two‑dose publicly funded vaccination. After receiving two doses, protection against the monkeypox virus is about 90%; a single dose offers roughly 40%–80% protection. Even if vaccinated individuals become infected, their symptoms are milder than those of unvaccinated persons. Information on publicly funded vaccination sites can be found on the CDC’s website (https://gov.tw/3SG ) Additionally, individuals who do not meet the criteria for publicly funded vaccination but are assessed by a physician to have a genuine exposure risk may receive the monkeypox vaccine at their own expense at any of the eight contract travel‑medicine hospitals nationwide; related information can be found under the CDC’s website / International Travel and Health / Travel Medicine Outpatient section.
The CDC again urges the public, when traveling to endemic areas or domestic high‑risk settings, to practice self‑protection and avoid social venues where close contact with unknown persons may occur, and to monitor themselves and others for symptoms to reduce exposure risk. If skin lesions appear—such as rashes, vesicles, macules, papules, pustules—and fever, chills, headache, muscle aches, or lymphadenopathy (e.g., around the ears, armpits, neck, or groin) are present, one should wear a mask, seek medical care promptly, and inform the physician of travel history, exposure to risk settings, or relevant contacts. More information is available on the CDC’s website (https://www.cdc.gov.tw) or call the domestic toll‑free epidemic prevention hotline 1922 (or 0800-001922) for inquiries.
Source: Taiwan CDC
Data compiled: Sensory Management Office
