Broderick Claire, Nadjm Behzad, Smith Valerie, Blaze Marie, Checkley Anna, Chiodini Peter L, Whitty Christopher J M
Public Health England Malaria Reference Laboratory, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK.
Hospital for Tropical Diseases, London, UK.
BMJ. 2015 Apr 16;350:h1703. doi: 10.1136/bmj.h1703.
To examine temporal and geographical trends, risk factors, and seasonality of imported vivax malaria in the United Kingdom to inform clinical advice and policy.
Observational study.
National surveillance data from the UK Public Health England Malaria Reference Laboratory, data from the International Passenger Survey, and international climactic data.
All confirmed and notified cases of malaria in the UK (n=50,187) from 1987 to 2013, focusing on 12,769 cases of vivax malaria.
Mortality, sociodemographic details (age, UK region, country of birth and residence, and purpose of travel), destination, and latency (time between arrival in the UK and onset of symptoms).
Of the malaria cases notified, 25.4% (n=12,769) were due to Plasmodium vivax, of which 78.6% were imported from India and Pakistan. Most affected patients (53.5%) had travelled to visit friends and relatives, and 11.1% occurred in tourists. Imported P vivax is concentrated in areas with large communities of south Asian heritage. Overall mortality was 7/12,725 (0.05%), but with no deaths in 9927 patients aged under 50 years. Restricting the analysis to those aged more than 50 years, mortality was 7/2798 (0.25%), increasing to 4/526 (0.76%) (adjusted odds ratio 32.0, 95% confidence interval 7.1 to 144.0, P<0.001) in those aged 70 years or older. Annual notifications decreased sharply over the period, while traveller numbers between the UK and South Asia increased. The risk of acquiring P vivax from South Asia was year round but was twice as high from June to September (40 per 100,000 trips) compared with the rest of the year. There was strong seasonality in the latency from arrival in the UK to presentation, significantly longer in those arriving in the UK from South Asia from October to March (median 143 days) versus those arriving from April to September (37 days, P<0.001).
Travellers visiting friends and family in India and Pakistan are most at risk of acquiring P vivax, and older patients (especially those >70 years) are most at risk of dying; these groups should be targeted for advice before travelling. The risk of acquiring vivax malaria is year round but higher during summer monsoons, masked by latency. The latency of time to clinical presentation of imported vivax malaria in the UK is highly seasonal; seasonal latency has implications for pretravel advice but also for the control of malaria in India and Pakistan. A reduced incidence of vivax malaria in travellers may mean further areas of South Asia can be considered not to need malaria chemoprophylaxis.
研究英国输入性间日疟的时间和地理趋势、危险因素及季节性，为临床建议和政策提供依据。
观察性研究。
来自英国公共卫生英格兰疟疾参考实验室的国家监测数据、国际旅客调查数据以及国际气候数据。
1987年至2013年英国所有确诊并报告的疟疾病例（n = 50187），重点关注12769例间日疟病例。
死亡率、社会人口学细节（年龄、英国地区、出生和居住国家以及旅行目的）、目的地和潜伏期（抵达英国至症状出现的时间）。
在报告的疟疾病例中，25.4%（n = 12769）由间日疟原虫引起，其中78.6%从印度和巴基斯坦输入。大多数受影响患者（53.5%）前往探亲访友，11.1%为游客。输入性间日疟集中在有大量南亚裔社区的地区。总体死亡率为7/12725（0.05%），但50岁以下的9927名患者中无死亡病例。将分析限制在50岁以上人群，死亡率为7/2798（0.25%），70岁及以上人群增至4/526（0.76%）（调整后的优势比为32.0，95%置信区间为7.1至144.0，P < 0.001）。在此期间，年度报告病例数急剧下降，而英国与南亚之间的旅客数量增加。从南亚感染间日疟的风险全年存在，但6月至9月的风险是其他时间的两倍（每10万次旅行中有40例）。从抵达英国到就诊的潜伏期存在强烈的季节性，10月至3月从南亚抵达英国的患者潜伏期明显更长（中位数143天），而4月至9月抵达的患者潜伏期为37天（P < 0.001）。
前往印度和巴基斯坦探亲访友的旅行者感染间日疟的风险最高，老年患者（尤其是70岁以上者）死亡风险最高；这些人群在旅行前应作为建议对象。感染间日疟的风险全年存在，但夏季季风期间更高，且因潜伏期而被掩盖。英国输入性间日疟临床就诊时间的潜伏期具有高度季节性；季节性潜伏期不仅对旅行前建议有影响，对印度和巴基斯坦的疟疾控制也有影响。旅行者中间日疟发病率的降低可能意味着南亚更多地区可被视为无需进行疟疾化学预防。
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