国立感染症研究所

Exanthema subitum 2000-2020

(IASR Vol. 41 p211-212: December 2020)

　Exanthema subitum (ES) is a febrile exanthematous disease in infancy with a generally good prognosis, characterized by a fever that lasts about three days and exanthema with fever reduction. In the acute phase, loose stool/diarrhea, bulging anterior fontanel, eyelid edema, and occipital lymphadenopathy are observed. Mottled exanthema on both sides of the uvula, so-called Nagayama’s spots, may appear in the early phase of the disease.

Influenza 2019/20 season, Japan

(IASR Vol. 41 p191-193: November 2020)

　The 2019/20 influenza season (from week 36 in September 2019 to week 35 in August 2020) was characterized by the predominance of the influenza A/H1pdm09 subtype, and influenza B, mainly Victoria lineage, also increased from week 51 in 2019.

HIV/AIDS in Japan, 2019

(IASR Vol. 41 p175-176: October 2020)

　HIV/AIDS surveillance in Japan started in September 1984. It was conducted under the AIDS Prevention Law between February 1989 and March 1999, and has operated under the Infectious Diseases Control Law since April 1999. Under the law, physicians must notify all diagnosed cases (see http://www.niid.go.jp/niid/images/iasr/34/403/de4031.pdf). The data presented in this article are from the annual report of the National AIDS Surveillance Committee for the year 2019 (published by the Tuberculosis and Infectious Diseases Control Division, the Ministry of Health, Labour and Welfare (MHLW), https://api-net.jfap.or.jp/status/japan/nenpo.html).

Rubella and congenital rubella syndrome in Japan as at July 2020

(IASR Vol. 41 p153-154: September 2020)

　Rubella is an acute infectious disease caused by the rubella virus, and is characterized by fever, rash, and lymphadenopathy. Rubella virus infection in pregnant women, especially up to 20 weeks of gestation, may result in prenatal transmission to the fetus and congenital rubella syndrome (CRS), which presents as various manifestations including heart defect, hearing loss, and cataract. Although there are no specific treatments for rubella or CRS, they can be prevented by rubella-containing vaccines.

Japanese spotted fever 1999-2019

(IASR Vol. 41 p133-135: August 2020)

　Japanese spotted fever is a tick-borne rickettsiosis that has been recently increasing; it was first reported in 1984 in Tokushima prefecture, Japan, based on the difference in the Weil-Felix reaction for scrub typhus (tsutsugamushi disease), which is endemic in Japan. It is caused by Rickettsia japonica, an obligate intracellular bacterium classified as a member of the spotted fever group rickettsia, causing fever and rash as major symptoms. Tick-bite sites and eschars are found in many patients. The rash extends from the extremities to the trunk, and is also noted on the palms and soles. The bite site is often smaller than that of scrub typhus, which is clinically similar. The primary risk of infection is outdoor activity and the incubation period from tick bite to disease onset is 2-8 days, which is shorter than that of scrub typhus (5-14 days). Japanese spotted fever is a Category Ⅳ Infectious Disease that requires reporting of all cases under the Act on the Prevention of Infectious Diseases and Medical Care for Patients of Infection (Infectious Diseases Control law; notification criteria are available at https://www.niid.go.jp/niid/images/iasr/38/448/de4482.pdf). Clinical differentiation from scrub typhus is difficult and laboratory diagnosis is required for notification.

COVID-19 as of May 2020

(IASR Vol. 41 p103-105: July 2020)

　Coronaviruses are enveloped, positive-sense single-stranded RNA viruses. Coronaviruses known to infect humans include four causative viruses of the common cold, human coronavirus 229E, OC43, NL63, and HKU1, and severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) and Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV), both of which cause severe pneumonia. SARS-CoV-2, the cause of coronavirus disease 2019 (COVID-19), which was first identified in December 2019, is classified in the same Betacoronavirus genus as SARS-CoV with high genetic homology (approximately 80%), and was reported to bind and enter human cells using the receptor ACE2.

Enterohemorrhagic Escherichia coli (EHEC) infection as of March 2020 in Japan

(IASR Vol. 41 p65-66: May 2020)

    Enterohemorrhagic Escherichia coli (EHEC) is an important diarrheagenic E. coli that produces Verotoxin/Shiga toxin (VT/Stx) and/or possesses VT-encoding genes. The main signs/symptoms of EHEC infections are abdominal pain, watery diarrhea, and bloody diarrhea. Fever (≥38°C) and/or vomiting are occasionally observed. VT-producing EHEC can cause hemolytic uremic syndrome (HUS), which involves thrombocytopenia, hemolytic anemia, and acute renal failure; complications, such as encephalopathy, may develop, with potentially fatal outcomes.

Dengue fever and dengue hemorrhagic fever, 2015-2019

    Dengue fever (DF) is an infectious disease caused by the dengue virus (DENV). DENV belongs to the genus Flavivirus of the family Flaviviridae and consists of four serotypes, DENV-1, -2, -3, and -4. DENV is one of the mosquito-borne arboviruses, and the main vectors are Aedes aegypti and Ae. albopictus. DENV is mainly maintained in the human-to-mosquito-to-human transmission cycle. Currently, Ae. aegypti is not distributed in Japan, but Ae. albopictus inhabits a wide area excluding Hokkaido (see pp.91 & 92 of this issue). DENV infection in humans causes symptoms, such as fever, exanthema, and joint and muscle pain, after an incubation period of approximately 4 to 14 days (DF). In many cases, patients recover without sequelae. However, some DF patients develop severe symptoms, such as hemorrhage and/or neurological symptoms, including deterioration in consciousness, and may die due to multiple organ failure. Such a disease state is called severe dengue fever (SDF), and includes dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). There is no specific treatment for DF. A dengue vaccine is licensed and available in some countries (see p.99 of this issue). DF is mainly endemic in tropical and subtropical regions (see p.93 of this issue). Most DF patients in Japan were those, including returnees, infected with DENV in the endemic regions. Autochthonous outbreaks of DF were reported in 2019 for the first time in five years since 2014 (see p.94 of this issue).