結核病的群聚顯示南非愛滋病毒錯失治療的地方
Keith Alcorn / 2019年8月27日/ aidsmap news/ 財團法人台灣紅絲帶基金會編譯
根據在南非誇祖魯–納塔爾省於7月在Nature Scientific Reports上發表的研究，結核病（TB）新病例的群聚提供了強有力的證據，證明這些地區需要優先考慮去改善抗反轉錄病毒治療（ART）的覆蓋範圍，且改善ART的覆蓋範圍與結核病新感病例的減少有關 。
結核病是南非單一最大的死亡原因，而愛滋病毒感染者罹患病時發展成為活動性結核之風險特別高。抗反轉錄病毒治療因其恢復了免疫系統可降低結核病的發展風險。
自20世紀90年代初以來，南部非洲的愛滋病毒流行大大增加了該地區的結核病負擔，雖然抗反轉錄病毒治療的可用性與結核病例的減少有關，但關於如何最好地針對結核病控制努力上的信息仍然缺乏。
建模研究
雖然最近的模型研究發現抗反轉錄病毒覆蓋率與結核病發生率降低之間存在很強的相關性，但結核病似乎並未在社區中平均分佈。來自南非的結核病例報告顯示，結核病發生率最高的地區並不總是與愛滋病毒感染率最高的地區相匹配。
誇祖魯 – 納塔爾省非洲健康研究所的研究人員，調查了該省北部農村地區結核病的地理分佈與抗反轉錄病毒的涵蓋率之間的關係。利用自2000年以來系統收集的人口健康數據，他們隨時間進展繪製了自我報告的結核病病例的分佈情況，以確定病例在時間和空間上的群聚。
通過繪製這些群聚圖，研究人員可以確定該區域可能的傳播焦點，查看這些位置是否隨時間發生變化，並評估與該區域結核病分佈相關的地理和社會人口學因素 – 包括HIV和ART的覆蓋率。
本地區的結核病病例通報率極高。於 2008年，病例之通報在每10萬居民中達到1,773例的高峰，並在2014年下降至每10萬人756例。相比之下，英國2018年最高的結核病通報率是在倫敦，為每10萬人21例。
研究對象人群包括所有15歲及以上的成年人，他們在2009年至2015年期間至少回答了一份個人健康調查問卷（41,812人，約60％為女性）。通過自我報告評估結核病發生率，並通過地理定位標記受訪者的位置。
研究人員發現，每年平均有3.2％的受訪者於最近確診為結核病，但結核病盛行率在2011年後開始下降。相較之下，南非的國家研究發現在2012年整個國家自我報告的結核病發生率為0.6％ 。
個案在時間和空間上聚集成九個群聚，四個最大的群聚聚集在毗鄰該區東南部主要公路的城郊區域。在整個研究期間，三個群集持續存在，表明該地區存在大量活躍的病例。
愛滋病毒盛行率從2009年的22％變為2012年的25％。在2012年，有超過一半（52％）的愛滋病毒感染者接受了抗反轉錄病毒治療。
多變項模型分析顯示在控制了家庭收入、年齡和其他社會人口學因素後，該地區內社區的ART覆蓋率每增加1％抗反轉錄病毒治療，則最近被診斷患有結核病的機率下降2％（調整後的勝算比為0.98，95％信賴區間為 0.97-0.99）。
儘管該研究依賴於自我報告的結核病診斷，但研究人員表示，結核病例的群聚與該地區耐藥性結核病例的模式一致，而這些病例則依賴於實驗室確認。
研究人員得出結論，他們的研究結果支持制定「精確的公共衛生策略」，該策略使用在地化數據來識別可能從加強愛滋病毒和結核病診斷上獲益的社區，促使人們接受治療，並增加愛滋病毒感染者中病毒載量受到完全抑制之比例。
TB clusters show where HIV treatment is missing in South Africa
Keith Alcorn/ 27 August 2019/ aidsmap news
Clusters of new cases of tuberculosis (TB) provide strong evidence of areas that need to be prioritised for improved antiretroviral therapy (ART) coverage, and improved ART coverage is associated with a reduction in new TB cases, according to research carried out in KwaZulu-Natal province, South Africa, published in July in Nature Scientific Reports.
TB is the single largest cause of death in South Africa and people living with HIV are at especially high risk of developing active TB. Antiretroviral treatment reduces the risk of developing TB as it restores the immune system.
The HIV epidemic in southern Africa has greatly increased the burden of TB in the region since the early 1990s, and although antiretroviral treatment availability is correlated with a reduction in TB cases, information is still lacking on how best to target TB control efforts.
Although a recent modelling study found a strong correlation between antiretroviral coverage and reductions in TB incidence, TB does not appear to be evenly distributed in the community. TB case reporting from South Africa suggests that the areas of highest TB incidence do not always match the areas of highest HIV prevalence.
Researchers at the Africa Health Research Institute in KwaZulu-Natal investigated the relationship between the geographical distribution of TB and antiretroviral coverage in a northern rural district of the province. Using data on the health of the population gathered systematically since 2000, they mapped the distribution of self-reported cases of TB over time to identify clustering of cases in time and space.
Mapping these clusters allowed the researchers to identify likely focal points of transmission in the district, to see if these locations changed over time and to assess the geographical and demographic factors – including HIV and ART coverage – associated with the distribution of TB in the district.
The district had an extremely high TB case notification rate. In 2008, case notifications peaked at 1773 cases per 100,000 inhabitants and declined to 756 cases per 100,000 in 2014. In comparison, the highest TB notification rate in the United Kingdom in 2018 was 21 cases per 100,000 in London.
The study population comprised all adults aged 15 and over who answered at least one individual health questionnaire between 2009 and 2015 (41,812 persons, approximately 60% women). TB incidence was assessed by self-report and the location of the respondent was tagged by geolocation.
The researchers found that an average of 3.2% of respondents per year had recently diagnosed TB, although TB prevalence began to decline after 2011. In comparison, South African national research found a self-reported TB rate for the entire country of 0.6% in 2012.
Cases were clustered in time and space into nine clusters, and the four largest clusters were grouped in a periurban area adjacent to a major highway in the south-east of the district. Three clusters persisted throughout the study period, indicating that a high number of active cases were present in this area.
HIV prevalence varied from 22% in 2009 to 25% in 2012. Just over half (52%) of people with HIV were on antiretroviral treatment in 2012.
Multivariate modelling that controlled for household income, age and other demographic factors, and antiretroviral treatment showed that for every 1% increase in ART coverage in communities within the district, the odds of being recently diagnosed with TB fell by 2% (adjusted odds ratio 0.98, 95% CI 0.97-0.99).
Although the study relied on self-report of TB diagnosis, the researchers say that the clustering of TB cases is consistent with the pattern of drug-resistant TB cases in the district, which are reliant on laboratory confirmation.
The researchers conclude that their findings support the development of “precision public health strategies” which use localised data to identify communities that may benefit from intensified efforts to diagnose HIV and TB, initiate people on treatment and increase the proportion of people with HIV who have fully suppressed viral load.
References
Tomita A et al. Space-time clustering of recently-diagnosed tuberculosis and impact of ART scale-up: evidence from a hyper-endemic rural South African population. Nature Scientific Reports, 9: 10724, 2019. https://doi.org/10.1038/s41598-019-46455-7