結核は空気感染するため、学校における結核感染対策は重要である。これまでの研究で、慶應義塾大学の外国人留学生、特に結核高蔓延国出身者の結核感染率が高いことが推測された。本学における適切な結核感染対策を検討するため、今年度も引き続き、本学に在籍する外国人留学生の結核感染状況を調査した。2016年9月から2018年9月にかけて、外国人留学生 206名を対象に、インターフェロンγ遊離試験(IGRA)による結核感染診断を行った。外国人留学生のIGRA陽性者は8名(3.9%)であり、推定結核罹患率(人口10万対)100以上の国の出身者の陽性率は9.4%、推定結核罹患率(人口10万対)100未満の国の出身者の陽性率は2.0%であった。推定結核罹患率100以上の国の出身者は、推定結核罹患率100未満の国の出身者に比べ、結核感染率が有意に高いと推測された。グローバル化に伴い外国人留学生が増加傾向にある本学においては、結核高蔓延国出身者を対象とした結核感染スクリーニングが、結核感染対策上、重要と考えられた。
医療施設は多くの免疫不全者や高齢者がおり、結核の集団感染の危険性が高い。そのため、医療従事者の結核感染対策は重要である。本学の医療従事者における適切な結核感染対策を検討するため、本学大学病院の職員の結核感染リスクを評価した。2010年8月から2015年12月まで、328人の職員を対象に、定期的に実施したIGRAの結果から結核感染危険率を推定した。IGRAが陽転した場合を新規結核感染と仮定すると、結核感染危険率は、0.149/100人・年と推定された。本学の医療従事者の結核感染危険率は、結核罹患率が低い(人口10万対50未満)国の医療従事者の結核感染危険率(3.81/100人・年)と比べると低いと推測されたが、引き続き結核感染予防に注意を払う必要性がある。
Measures against tuberculosis (TB) infection are critical in the university setting because it is an airborne disease. The previous study found a high estimated rate of TB infection among foreign-born students enrolled in Keio University, particularly those from countries with a high burden of TB. To propose the most optimal measures against TB infection at Keio University, we distributed a TB infection survey to foreign-born students for the 2018 fiscal year. We recruited 206 foreign-born students enrolled in Keio University between September 2016 and September 2018. Interferon-gamma release assays (IGRAs) were used to detect TB infection. Overall, 8 (3.9%) students tested positive on IGRA. A positive IGRA result was found in 9.4% of students from countries with an estimated TB incidence rate of ≥100 cases per 100,000 individuals, whereas 2.0% of those from countries with an estimated rate of <100 cases per 100,000 individuals were positive. Students from countries with an estimated incidence rate of ≥100 cases per 100,000 individuals had a significantly higher TB infection rate when compared with those from countries with an estimated incidence rate of <100 cases per 100,000 individuals. The number of foreign-born students at Keio University has increased with globalization; hence, it is essential to screen those students from countries with a high burden of TB.
Medical institutions are at high risk for TB outbreaks because they serve many immunocompromised and elderly patients. Therefore, taking measures against TB infection among health care workers (HCWs) is critical to prevent nosocomial TB outbreaks. In the present study, we assessed HCWs at Keio University to ascertain their risk of TB infection in an effort to determine the most optimal screening measures. We prospectively conducted serial IGRAs on 328 HCWs between August 2010 and December 2015. When assuming that all IGRA-positive conversions were attributable to true infection, the incidence of TB infection in HCWs was 0.149/100 person-years. Serial IGRA results estimated a low annual incidence of TB infection among the HCWs at Keio University compared with that in the HCWs from countries with low (<50 cases per 100,000 population) TB incidence (3.81/100 person-years), but continued vigilance is essential to eradicate TB infection.