Background : The number of Japanese people traveling abroad and foreigners coming to Japan has substantially increased ; however, resources for diagnosis and treatment of tropical and emerging diseases are limited in rural medical institutions. Although previous studies have described the characteristics of post-travel health problems in Japan, most of them were carried out in urban areas. Here, we describe the characteristics of patients at a rural hospital returning from overseas tropical destinations to consider measures against tropical and emerging diseases. Methods : In this single-center retrospective observational study, the characteristics of post-travel patients who visited Toyama University Hospital between January 2013 and December 2019 were collected from medical records. Continuous variables were represented as the mean and standard deviation or median and Inter-Quartile Range (IQR). Categorized variables were compared by Fisherʼs test. The threshold for significance was p＜0.05. Results : Sixty-five patients visited our hospital after travelling abroad during the study period. The most popular travel destination and reason for travel were Southeast Asia (53.8%) and leisure (49.2%), respectively. Only 6 (9.2%) patients had attended a pre-travel consultation. Short-term travelers (n=45 ;69.2%) were more numerous than long-term travelers (n=20 ; 30.8%), and most travelers went to Southeast Asia (n=30 ; 66.7%). Short-term travelers were less likely to attend pre-travel consultations than long-term travelers (4.76% vs 71.43%, p=0.0012). The most common diagnosis was gastrointestinal infection (30.8%) followed by dengue fever (7.7%). Conclusion : In todayʼs globalized society, an increasing number of patients with travel-related illnesses are expected, and thus, measures for the prevention and treatment of tropical and emerging diseases are necessary. Especially in regional districts, travelers should be made aware of the importance of visiting a travel clinic before travel.

国はCOVID-19 の家庭内感染予防のために宿泊療養を推奨しているが，療養開始時期と家庭内感染発生率の関係は明らかになっていない．COVID-19 は発症2日前から感染性があり，発症直後にウイルス量が最も多いと言われていることから，診断後早期に宿泊療養を開始しても，既に家庭内感染が成立している可能性も考えられた．そこで我々は，宿泊療養を行った家庭内での初発患者1,075名を対象に，発症2日前から療養開始までの期間（感染曝露期間）と家庭内感染発生率の関係を検討した．同居する世帯で1名以上2次感染者が発生した場合に家庭内感染発生ありとし，家庭内感染が発生した世帯数を，対象の全世帯数で除したものを家庭内感染発生率とした．感染曝露期間ごとの家庭内感染発生率では，3 日までは発生がみられず， 7 日で22.6％（95％信頼区間16.9％～29.5％），12 日以上では45.5％（95％信頼区間21.3％～72.0％）となっていた（回帰式y＝0.037x-0.047 R²＝0.863 p＜0.01）．本研究の結果からは，感染曝露期間が長いほど家庭内感染発生率が上昇しており，感染曝露期間が7日内（発症後5 日以内）に施設療養を行えば，家庭内感染発生率を半減（7日間22.6％，12日間以上45.5％）できる可能性が示唆された．

We report a case series of adult-onset human metapneumovirus (hMPV) pneumonia, which was difficult to distinguish from SARS-CoV-2 infection (COVID-19) and was thought to have spread among healthy adults in the community. [Case 1] A 60-year-old man visited the hospital complaining of cough and fever. Chest CT showed bilateral multiple ground-glass opacities, suggestive of atypical pneumonia, including COVID-19. The PCR test result for SARS-CoV-2 was negative, and the additionally performed FilmArray respiratory panel test revealed a positive result for hMPV. [Case 2] A 60-year-old man who was a colleague of Case 1 visited the hospital complaining of cough, runny nose, headache, and fever. He was diagnosed as having an upper respiratory tract infection without performing any rapid antigen tests. [Case 3] A 60-year-old woman who was the wife of Case 2 visited the hospital complaining of cough and fever. Chest CT showed ground-glass opacities and multiple nodular shadows, and the rapid antigen test result for hMPV was positive. Based on the epidemiological association and similarity of symptoms, all the three cases were considered as having hMPV infection. Case 1 and Case 2 were suspected of having become infected at work, and Case 3 was suspected to have been transmitted from Case 2 in the home. In summary, careful differential diagnosis between hMPV and SARS-CoV-2 is required, especially during epidemics of hMPV in the current SARS-CoV-2 pandemic era.

Patients with coronavirus disease 2019 (COVID-19) often present with multiple symptoms such as cough, dyspnea and olfactory dysfunction, however, cervical lymphadenopathy is a relatively rare clinical sign. We report two patients with COVID-19 who presented with a clinical picture similar to that of subacute necrotizing lymphadenitis (Kikuchi-Fujimoto disease) after improvement of the acute symptoms of COVID-19. As systemic steroid therapy was markedly effective in both patients, we speculate that the lymphadenitis could have been caused by an immune reaction during reduction of the virus titers. When cervical lymphadenopathy and recurrent fever are observed after improvement of the acute symptoms in COVID-19 patients, the possibility of a Kikuchi-Fujimoto disease-like condition should be considered and corticosteroid treatment undertaken if the symptoms are prolonged.

Balamuthia mandrillaris is one of the free-living amoebae that causes potentially fatal cutaneous and central nervous system infection. Both the diagnosis and treatment are challenging, especially when the central nervous system is involved. Herein, we report a case of granulomatous amoebic encephalitis caused by B. mandrillaris, in a patient who presented with subcutaneous lesions. A 55-year-old patient with a history of ANCA-associated vasculitis who was on maintenance dialysis was referred to our hospital for investigation and treatment of an intracranial lesion. He had had multiple subcutaneous nodules for nine months before the referral, which had been histopathologically diagnosed about a month prior to the referral as granulomatosis with polyangiitis. Brain MRI showed a space-occupying lesion with surrounding edema in the left occipital lobe. Brain biopsy was performed, and the histopathological diagnosis was epithelioid cell granuloma； no pathogen could be identified. Suspecting either deterioration of granulomatosis with polyangiitis or infection, the patient was started on treatment with a corticosteroid and several antibiotics, antifungal, and antiprotozoal agents. However, the intracranial lesion continued to progress despite all the treatment, and the patient died on the 33rd hospital day. Further investigation at the National Institute of Infectious Diseases revealed B. mandrillaris infection in both the subcutaneous and intracranial lesions. From our experience of this case, we suggest that B. mandrillaris infection be included in the differential diagnosis in patients presenting with cutaneous granulomatous lesions of unknown cause； early diagnosis, before the amoeba invades the central nervous system, is of critical importance.