Between June 2016 and mid-May 2017, an unusual increase in cases of hepatitis A affecting mainly men who have sex with men (MSM) has been reported particularly by low endemicity countries in the European Region, and in the Americas (Chile and the US).
In the European Region, 15 countries (Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, the Netherlands, Norway, Portugal, Slovenia, Spain, Sweden, and the United Kingdom) reported 1173 cases related to the three distinct multi-country hepatitis A outbreaks as of 16 May 2017.
In Chile, 706 hepatitis A cases were reported at national level as of 5 May 2017. In the US, the New York City Health Department has noted an increase in hepatitis A cases among MSM who did not report international travel.
In low endemicity settings, WHO recommends hepatitis A vaccination for high-risk groups, such as travellers to endemic areas, MSM, people who inject drugs, and chronic liver disease patients.* For MSM the main risk factor is related to sexual transmission, particularly oral-anal sexual contact. Most of the affected countries have routinely recommended hepatitis A vaccine for MSM.
This event is of particular concern from a public health perspective because of the current limited availability of hepatitis A vaccine worldwide.
In this regard, WHO requests countries to report to WHO Regional IHR Contact points any unusual increase in the number of hepatitis A cases among MSM.
WHO risk assessment
Infection with hepatitis A virus is typically acute and self-limiting. Hepatitis A infection does not cause chronic liver disease and is rarely fatal. Some patients may develop more severe symptoms which may last up to a few months. The virus is primarily spread when an uninfected (and unvaccinated) person ingests food or water that is contaminated with the feces of an infected person. The virus can also be transmitted through close physical contact with an infectious person, through dirty hands and through sexual contact.
In low endemicity countries, reported rates of hepatitis A are low. Disease may occur among adolescents and adults in high-risk groups, such as injecting-drug users, MSM, people travelling to areas of high endemicity, and in isolated populations, such as closed religious communities.
So far, no fatalities have been reported in connection with the ongoing outbreaks. It has the potential to spread further to the general population if control measures (vaccination, hygiene, food safety, and safer sex measures) are not implemented.
WHO’s to-do list
- Countries with low endemicity profile for hepatitis A should routinely offer vaccination to individuals at increased risk of hepatitis A and of a serious complications following infection. The recommended risk groups, among others, include men who have sex with men. Vaccination against hepatitis A should be included as part of a comprehensive package of services to prevent and control of viral hepatitis, including health education and measures for outbreak control.
- Use of hepatitis A vaccine should be preferred for pre- and post-exposure prophylaxis (e.g. for close contacts of acute cases of hepatitis A).
- Countries may consider single-dose schedule for hepatitis A vaccination to control outbreaks of hepatitis A, especially when vaccine availability is scarce.
- Public health messaging should be directed at groups at increased risk of hepatitis A and of serious complications from the infection.
- Information should include advice on prevention – vaccination, hygiene, food safety and safer sex measures.
*In intermediate endemicity setting, hepatitis A vaccination can be considered for the whole population, while in high endemicity, infections are common, but the disease is uncommon, hence, the vaccine is not recommended.