‘All the characteristics’: Hepatitis E is a neglected tropical disease, experts say
Hepatitis E virus is associated with a high risk for mortality among pregnant women and has “profound consequences” for populations with poor access to clean water and sanitation services, yet receives little attention from public health, research and clinical communities, making it a “serious candidate” to be reclassified as a neglected tropical disease, researchers argued.
“When a patient has hep E, we have no therapeutics that work in general,” Andrew S. Azman, PhD, assistant scientist in the division of infectious disease epidemiology at Johns Hopkins Bloomberg School of Public Health, told Infectious Disease News.
“The public health community has had very little success stopping HEV outbreaks with current tools — for example, emergency water and sanitation improvements — and more investments are needed to advance the current generation of vaccines, improve diagnostics and enhance our estimates of burden,” Azman said. “Hep E has all the characteristics of a neglected tropical disease, as defined by the WHO, and gaining this designation officially can help direct resources toward this important disease.”
Writing in PLoS Neglected Tropical Diseases, Azman and colleagues noted that there are four genotypes of human HEV. Two genotypes, 3 and 4, are nonepidemic and zoonotic, and have gained attention in North America and Europe for their potential to be transmitted through food, blood transfusion and organ donation, the researchers wrote. Genotypes 1 and 2 (g1/g2), on the other hand, receive “relatively little attention” and cause outbreaks among populations with “poor access to safe water and sanitation infrastructure,” they said.
Azman and colleagues highlighted the evidence that HEV meets WHO’s four criteria for a neglected tropical disease.
First, the condition must disproportionally affect populations living in poverty and cause “important” morbidity and mortality that would justify a global response; and second, the affected populations must primarily be in tropical and subtropical areas. Azman and colleagues showed that HEV cases and outbreaks are primarily reported from tropical and subtropical areas, including countries in Africa and Asia with a low to medium human development index that report almost all HEV g1/g2 outbreaks. HEV causes an estimated 50,000 deaths, annually, and pregnant women are the most likely to die from HEV, with a case fatality risk of up to 30% in symptomatic patients.
Third, one or more of the five public health strategies adopted by the WHO department for control of neglected tropical diseases must be able to broadly control, eliminate or eradicate the condition. The researchers noted that the best prevention and control measure for HEV transmission is universal access to and use of “safely managed water and sanitation.” They also suggested that vaccination may help to reduce the disease burden.
“The vaccine is one tool we have at our disposal, and it simply has not been used in an outbreak to date,” Azman said. “The field deployment of the vaccine and documentation of its feasibility and effectiveness is one key area that we can be a game changer.”
Fourth, the condition has to have been “relatively neglected” by research for new diagnostics, medicines and other control tools. Azman and colleagues conducted a “nonexhaustive” search of grants recently awarded from three large biomedical research donors, which revealed very few HEV investments, and only one phase 3 trial of an HEV vaccine.
“Calling it a [neglected tropical disease] would open up a number of new channels for funding of basic and applied research, in addition to funding for surveillance and disease prevention,” Azman explained. – by Marley Ghizzone
Disclosures: The authors report no relevant financial disclosures.