Related Experiment Video
Updated: May 20, 2025
Development of a Hepatitis B Virus Reporter System to Monitor the Early Stages of the Replication Cycle
Published on: February 1, 2017
Hepatitis A outbreak among men who have sex with men, Shinjuku, Japan, 2018
Mariya Itaki1, Masayuki Endo1, Hiroyuki Asakura2
1Department of Health, Shinjuku City Office, Tokyo, Japan.
Insights
In 2018, Shinjuku City experienced a hepatitis A virus (HAV) outbreak primarily affecting men who have sex with men. Public health recommendations emphasize awareness of sexual transmission routes and timely hepatitis A vaccination for prevention.
Area of Science:
- Epidemiology
- Infectious Disease Outbreak Investigation
- Public Health
Background:
- In 2018, an unusual increase in hepatitis A virus (HAV) infections was identified in Shinjuku City.
- Hepatitis A is a viral infection that can spread through contaminated food or water, and also through close personal contact, including sexual contact.
Purpose of the Study:
- To characterize the 2018 hepatitis A outbreak in Shinjuku City.
- To identify transmission routes among hospitalized cases, particularly within the men who have sex with men (MSM) population.
- To provide recommendations for controlling and preventing future HAV infections in this demographic.
Main Methods:
- Collected data on HAV cases from the National Epidemiological Surveillance for Infectious Diseases system.
- Conducted inpatient interviews using semistructured questionnaires for detailed information.
- Analyzed epidemiological data, including demographics, vaccination status, and potential risk factors.
Main Results:
- A total of 131 HAV cases were reported in 2018, with 98% being male and 81% identifying as men who have sex with men.
- The majority of cases (31%) required hospitalization, with the highest proportions in the 30-39 and 40-49 age groups.
- Among hospitalized cases, coinfection with HIV, recent casual sexual contact, and use of social networking services (SNS) for partner acquisition were significant risk factors.
Conclusions:
- The 2018 Shinjuku City HAV outbreak predominantly impacted the men who have sex with men community.
- The identified outbreak strain is consistent with strains reported in similar outbreaks globally among MSM.
- Key prevention strategies include increasing awareness of HAV as a sexually transmitted infection, particularly via SNS, and promoting timely hepatitis A vaccination.
Objective:
In 2018, the Shinjuku City Department of Health detected excess cases of hepatitis A virus (HAV) infection. The objectives of this investigation were to characterize the outbreak, identify transmission routes among inpatient cases and make recommendations to control and prevent HAV infection among men who have sex with men.
Methods:
Information about cases of HAV infection was collected from the National Epidemiological Surveillance for Infectious Diseases system and inpatient interviews conducted by public health nurses in 2018.
Results:
There were 131 HAV cases in 2018. Of these, 98% (129/131) were male, of whom 81% (105/129) were men who have sex with men. Hospitalization was required for 40 cases (31%). The age groups with the highest proportion of cases were 30-39 and 40-49 years (each 34%; 44/131). Two cases (2%) had received the second dose of the HAV vaccine, but only 10 days before symptom onset; all others had received no doses. The sequence type subgroup 13, an RIVM-HAV-16-090-like strain, was seen in 51 cases (39%). Of the 40 hospitalized cases, 21 (53%) participated in an interview conducted using a semistructured questionnaire. Altogether, of 21 cases, 12 (57%) had coinfection with HIV, 13 (62%) had casual sexual contact within the preceding 2 months and 10 (48%) had used social networking services (SNS) to find a sexual partner.
Discussion:
In Shinjuku, this outbreak almost exclusively affected the population of men who have sex with men. The detected outbreak strain has previously been reported in outbreaks among men who have sex with men in China, Taiwan (China) and Europe. For HAV prevention, the most important measures are raising awareness of the risk of HAV as a sexually transmitted infection via SNS and promoting immunization at the appropriate time.
Related Concept Videos
01:26Sexually Transmitted Infections
01:23Infertility in Males
01:20Disorders of the Male Reproductive System
Prostate disorders are another major concern. These conditions can impair urinary flow due to the prostate's location around the urethra....
00:36Viral Mutations
01:43Sex-linked Disorders
01:17Transmission-based Precautions I: Contact, Enteric, and Droplets
Contact Precautions:
Contact precautions are the measures taken to prevent the transmission of infectious agents, especially epidemiologically important microorganisms such as MRSA or influenza, primarily transmitted through direct or indirect contact with an...