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.

The Japanese government recommends isolation at dedicated facilities for prevention of household transmission of COVID-19, however, the relation between the time of start of isolation at facilities and the household secondary attack incidence rate is still unknown. Since COVID-19 is contagious from 2 days prior to symptom onset and the viral load is the maximal just after the onset of symptoms, we thought that household infection could have already occurred even if the patient is isolated at a facility soon after the diagnosis. Therefore, we examined the relationship between the period from 2 days before symptom onset and the start of isolation at a facility (the infection exposure period) and the household secondary attack incidence rate among 1,075 index cases in households who were under isolation at facilities. We defined transmissions in households as cases in which household secondary transmission occurred to more than one person, and the household secondary attack incidence rate as the value obtained by dividing the number of households in which secondary transmission occurred by the total number of households. Evaluation of the household secondary attack incidence rate for each infection exposure period revealed that household secondary transmission did not occur in cases with an infection exposure period of 3 days, and the household secondary incidence rate was 22.6% (95% CI, 16.9%-29.5%) for an infection exposure period of 7 days, and 45.5% (95% CI, 21.3%-72.0%) for infection exposure periods of 12 days or more (regression analysis： y=0.037x 0.047；R²=0.863；p＜0.01). These findings suggest that the household secondary attack incidence rate increased as the infection exposure period increased, and that the household secondary attack incidence rate could be reduced to half (from 45.5% for an infection exposure period of 12 days to 22.6% for a period of 7 days) if we could start isolation so as to keep the infection exposure period at 7 days or less (5 days or less after the onset).

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.