日本正面臨近年來最嚴重的百日咳疫情，感染人數持續飆升且沒有減緩跡象。今年累計病例數已突破六萬例，遠遠超過往年全年紀錄。以7月中為例，累計病例已達約五萬二千多例，單週新增病例一度高達三千五百餘例，創下自2018年採用現行統計方式以來的最高紀錄。相比之下，2024年全年僅有約四千例，顯示今年疫情的擴散速度與規模極為驚人。

從年初到五月底的前二十一週，累計病例數已達二萬二千多例，是去年全年的五倍以上。六月底時，病例數更逼近四萬例，之後仍一路攀升。疫情已波及各年齡層，其中十至十九歲的青少年感染比例最高，佔比達近六成。專家指出，這與疫苗免疫力會隨時間減弱有關，許多青少年與成人因未接種追加劑而成為帶菌者，對尚未接種的嬰幼兒構成巨大威脅。

目前尚未找出這波疫情持續高發的單一原因，但多重因素可能同時作用。百日咳本身的傳染力極高，基本傳染數可達十二至十六，與麻疹相當。此外，日本部分地區已檢出具抗藥性的細菌株，使得常用抗生素的治療效果下降，增加控制難度。再加上疫苗保護力隨時間衰退，以及疫情後期人群免疫屏障出現漏洞，讓疫情得以快速蔓延。

日本政府已呼籲民眾盡快完成百日咳疫苗接種，特別是嬰幼兒、青少年與孕婦等高風險群體，以降低重症與死亡的風險。同時，官方也強調必須加強衛教宣導、提升診療速度與正確性，並鼓勵社會大眾提高防疫警覺。這場疫情不僅反映傳染病防控的脆弱點，也提醒人們，唯有醫療體系與全民防疫意識並進，才能有效遏止疫情持續擴散。

Japan is currently facing its most severe whooping cough (pertussis) outbreak in recent years, with infection numbers continuing to surge without signs of slowing down. The total number of reported cases this year has already exceeded 60,000, far surpassing the annual records of previous years. For example, by mid-July, cumulative cases had reached over 52,000, with a single-week increase of more than 3,500 cases — the highest figure since the current statistical method was adopted in 2018. In comparison, there were only about 4,000 cases in the whole of 2024, highlighting the alarming speed and scale of the current spread.

From the start of the year to the end of May, the cumulative number of cases in the first 21 weeks already stood at more than 22,000 — over five times higher than the total for last year. By the end of June, the number had nearly reached 40,000 and has continued climbing since then. The outbreak has affected people of all age groups, but teenagers aged 10 to 19 account for the highest proportion, making up nearly 60% of all cases. Experts point out that this is related to the waning immunity of vaccines over time, with many teenagers and adults not receiving booster shots, thereby becoming carriers and posing a significant threat to unvaccinated infants and young children.

So far, no single definitive cause has been identified for the sustained high transmission in this outbreak, but multiple factors may be at play. Whooping cough is inherently highly contagious, with a basic reproduction number (R₀) ranging from 12 to 16, comparable to measles. In addition, antibiotic-resistant bacterial strains have been detected in certain regions of Japan, reducing the effectiveness of commonly used treatments and complicating containment efforts. The gradual decline in vaccine-induced protection and gaps in herd immunity have also contributed to the rapid spread.

The Japanese government has urged the public to complete their whooping cough vaccinations as soon as possible, particularly infants, teenagers, and pregnant women — all considered high-risk groups — in order to reduce the risk of severe illness and death. Authorities have also stressed the need to strengthen public health education, improve diagnostic speed and accuracy, and encourage higher levels of public awareness. This outbreak not only exposes weaknesses in infectious disease control but also serves as a reminder that only a combination of robust medical systems and strong public vigilance can effectively curb the continued spread of the epidemic.