Fever is a common symptom of influenza and coronavirus disease 2019 (COVID-19), yet its physiological role in host resistance to viral infection remains less clear. Here, we demonstrate that exposure of mice to the high ambient temperature of 36 °C increases host resistance to viral pathogens including influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). High heat-exposed mice increase basal body temperature over 38 °C to enable more bile acids production in a gut microbiota-dependent manner. The gut microbiota-derived deoxycholic acid (DCA) and its plasma membrane-bound receptor Takeda G-protein-coupled receptor 5 (TGR5) signaling increase host resistance to influenza virus infection by suppressing virus replication and neutrophil-dependent tissue damage. Furthermore, the DCA and its nuclear farnesoid X receptor (FXR) agonist protect Syrian hamsters from lethal SARS-CoV-2 infection. Moreover, we demonstrate that certain bile acids are reduced in the plasma of COVID-19 patients who develop moderate I/II disease compared with the minor severity of illness group. These findings implicate a mechanism by which virus-induced high fever increases host resistance to influenza virus and SARS-CoV-2 in a gut microbiota-dependent manner.

Some countries have reported a post-pandemic resurgence in syphilis prevalence, but trend data in the World Health Organization Western Pacific Region (WHO-WPRO), including Japan, are severely lacking. Thus, the present study compares the number of syphilis cases before and after the COVID-19 pandemic in some WHO-WPRO countries. In addition, temporal trends in the number of syphilis cases in Japan pre- and post-pandemic are described. Annual numbers of syphilis cases during the study periods from China, New Zealand, Australia and Japan were compared. Annual trends of the numbers of syphilis cases during the same study periods were examined in Japan. In 2020, the number of syphilis-positive cases decreased in all four countries. In 2021, though, China, Australia and Japan all showed an increase in the numbers of syphilis cases. However, the rate of increase in China (+2.8%) and Australia (+4.8%) was low compared to Japan (+36.0%). The number of syphilis cases in New Zealand in 2021 was 12.6% lower than in 2020. In 2022, the number of cases of syphilis in China was 7.4% lower than in 2021. The increase of syphilis-positive cases was approximately 6.3-fold higher in Japan compared to Australia (+66.2% vs. +10.5%) in 2022. In conclusion, post-pandemic resurgence of syphilis occurred in Australia and Japan, but not in China and New Zealand. The reason for the substantial increase in syphilis-positive cases in Japan remains unclear. Post-pandemic, prevention and control of sexually transmitted infections still require attention.

The Coronavirus disease 2019 (COVID-19) pandemic and people's subsequent behavioral changes have decreased the cases of respiratory infection worldwide. However, research on infectious diseases with other transmission modes is insufficient. The aim was to assess the impact of the COVID-19 pandemic on non-respiratory infectious diseases: infectious enterocolitis, sexually transmitted diseases such as human immunodeficiency virus (HIV) infection and syphilis, and tick-borne diseases. This retrospective, cohort study used comprehensive surveillance data from the National Institute of Infectious Diseases in Japan from January 1, 2018, to December 31, 2021. The number of cases of infectious diseases before the COVID-19 pandemic (2018–2019) was compared with that during the COVID-19 pandemic (2020–2021). Reduction rates were calculated as the number of disease cases during the COVID-19 pandemic in 2020 and 2021, respectively, divided by the mean number of disease cases in 2018 and 2019. The total numbers of cases of infectious enterocolitis, sexually transmitted diseases, and tick-borne diseases during the study period were 2,507,304 cases, 24,972 cases, and 3012 cases, respectively. The number of cases decreased for infectious enterocolitis and sexually transmitted diseases during the COVID-19 pandemic compared with before the COVID-19 pandemic, with an approximately 40–50% decrease in enterocolitis and 30–55% decreases in sexually transmitted diseases. However, cases of tick-borne diseases changed little, with a 0.2% increase in 2020 and a 6% increase in 2021. The COVID-19 pandemic had a different impact on the number of cases of infectious diseases depending on their mode of transmission.

Background: Enterocytozoon bieneusi and Cryptosporidium spp. are prevalent zoonotic parasites associated with a high burden among children. To date only limited molecular epidemiological data on E. bieneusi and Cryptosporidium spp. in humans living in Thailand has been published. Methods: PCR-based tools were used to detect and characterize E. bieneusi and Cryptosporidium spp. The internal transcribed spacer (ITS) region of the rRNA gene was used to investigate E. bieneusi, and the small subunit (SSU) rRNA gene was used to investigate Cryptosporidium spp., and 697 fecal samples from villagers and school children in rural areas in Thailand were analyzed. Results: The infection rates were 2.15% (15/697) for E. bieneusi and 0.14% (1/697) for Cryptosporidium spp. The prevalence of E. bieneusi was significantly high in Loei province. Sequence analysis indicated that the Cryptosporidium isolate was C. parvum. Nine E. bieneusi genotypes were identified, EbpC, Peru12, TMH6, TMH3, TMH7, H, D, and two novel genotypes TMLH1 and TMLH2. E. bieneusi prevalence was significantly higher in male participants than in female participants, and in children aged 3–15 years than in participants aged > 15 years. Conclusions: The prevalence, genotypes, and zoonotic potential of E. bieneusi were found to vary significantly high even in one country. Transmission routes and key animal carriers of E. bieneusi may be associated with differences in hygiene, sanitation, and cultural behaviors. Further molecular studies including longitudinal studies will be required to unveil epidemiological characteristics of these opportunistic intestinal protozoa in all over the countries.

This study aimed to determine whether the current syphilis resurgence in Japan is attributable to incident syphilis in people living with HIV (PLWH). This observational, retrospective, population-based study used data from the Japanese National Database. Data were extracted for PLWH who received antiretroviral treatment between January 2009 and December 2018. Using these data, along with the annual number of PLWH and syphilis diagnoses in the total population of Japan acquired from the National Institute of Infectious Diseases, the fraction of PLWH with syphilis compared to the total number of syphilis patients reported each year was calculated. There was a dramatic increase in syphilis cases during the study period. However, the incidence of syphilis in PLWH was stable during 2010-2018; the fraction of PLWH with newly diagnosed syphilis remaining at approximately 2% of the total PLWH cases in Japan each year. The proportion of newly diagnosed syphilis cases in PLWH decreased during the study period and accounted for 50 years was observed (7.4% in 2010 to 10.4% in 2014 and 14.9% in 2018). The recent dramatic increase in syphilis cases in Japan was not seen in PLWH. Thus, the resurgence of syphilis in Japan cannot be attributed to its transmission in the PLWH population.

Ukraine has a historically high burden of tuberculosis (TB). As a result of many years of the healthcare system’s reformation, the epidemiological situation has improved. However, under the influence of the COVID-19 pandemic and the illegal invasion by Russia, fluctuations in incidence occur. Through a retrospective, observational analysis using data from the Public Health Center of the Ministry of Health of Ukraine, this study tracked the incidence of TB and multidrug-resistant tuberculosis (MDR TB) and highlights changes caused by crises. The region that maintained a consistently high level of TB and MDR TB throughout the entire study period was Southeastern Ukraine. Data analysis showed a significantly increased TB incidence in Central Ukraine in 2022–2023 (62.75 per 100,000 population) versus 36.55 per 100,000 population in the 2013–2019 period. In Eastern Ukraine, TB incidence decreased markedly (14.95 per 100,000 population) after the beginning of the war in 2022 compared with the pre-COVID-19 pandemic 2013–2019 period (50.36 per 100,000 population). These results indicate a changing pattern of TB incidence throughout Ukraine during the conflict, with lower rates in conflict-affected areas and higher rates in host regions. This reflects the importance of strengthening TB surveillance and control strategies adapted to areas experiencing population influx.