Due to the recent increase in HAV infection in Brazil, the Ministry of Health has extended the indication of HAV vaccine to individuals who practice oral-anal sex, especially among MSM [14
]. However, the strains responsible for these cases have not yet been characterized.
The couple enrolled in this study reported unprotected anal-oral sex and multiple sexual partners. Studies in HAV outbreaks among MSM have shown such practices to be common among the infected cases [7
], reinforcing the sexual practice as the probable transmission route. In addition, coinfection with other STIs, such as HIV, syphilis and hepatitis B have been reported suggesting a high incidence of unprotected sex thus increasing exposure and promoting further transmission to enteric viruses such as HAV [8
]. The couple studied here presented concurrent HAV and HIV antibodies and serological evidence of past syphilis infection. Studies have shown that HIV-infected patients have elevated risk for HAV co-infection [15
]. Likewise, HIV co-infection can exacerbate HAV-associated liver damage and extend the HAV fecal excretion period [16
], increasing the risk of spread to others [12
], through water sources in areas that lack adequate sanitation.
Phylogenetic analysis showed a monophyletic cluster of genotype IA (aLRT = 0.94) enrolling the couple’s samples and sequences from the European MSM outbreaks, demonstrating that this strain (VRD_521_2016) is circulating in Rio de Janeiro, Brazil, and may or may not be limited to MSM. The mean evolutionary rate, estimated in 1.56 × 10−3
substitutions/site/year (95% HPD, 6.76 × 10−4
to 2.61 × 10−3
), is consistent with other studies on HAV genotype IA VP1-2A (1.21 × 10−3
substitutions/site/year) and HAV genotype I VP3-VP1-2A (5.56 × 10−4
]. The Bayesian inference revealed that the most recent common ancestor of the strain VRD_521_2016 might have been originated around 2013 in Europe (root of the clade) and may be introduced in Brazil between the second half of 2016 and the beginning of 2017. This strain was identified in July 2016 among UK MSM who travel to Spain [7
], and then detected in several MSM outbreaks in European countries [7
]. Approximately, 500,000 tourists visited Brazil due to the Olympic and Paralympic Games that took place between August to October 2016 in Rio de Janeiro, [21
] leading to an intense flow of people from several continents. Thus, it is possible that the strain VRD_521_2016 was introduced in Brazil during the Olympics and spread rapidly through sexual practices among MSM, being responsible for the increase in HAV infection in adult men in 2017 [13
]. Studies have shown that demographic changes are often associated with the introduction of new pathogens, as demonstrated by the spread of the ZIKA virus in 2015 [22
]. Nevertheless, while this strain may have been implicated in the increase in HAV among men in 2017 in Brazil, further studies involving sequencing of a larger samples should be implemented to test and to reinforce this hypothesis.
This study reports the introduction of the HAV strain VRD_521_2016 in Brazil, possibly linked to the intense tourism promoted by the Olympic Games. This reinforces the urgent need for health authorities to improve access to HAV vaccine to high-risk adult groups. Moreover, education measures are useful to prevent the spread of HAV to key populations.