Overlap of Sexually Transmitted HCV between U.S. and Europe
A phylogenetic analysis of more 200
hepatitis C virus (HCV) strains from HIV positive gay and
bisexual men revealed extensive clustering of related viruses
within U.S. cities, but little overlap between the East and
West coasts, or between the U.S. and Europe or Australia,
according to findings presented at the at the 18th Conference
on Retroviruses and Opportunistic Infection (CROI 2011) this
month in Boston.
past decade researchers have reported outbreaks of apparently sexually
transmitted acute hepatitis C among
HIV positive men who have sex with
men (MSM), first in the U.K., then in large cities in Europe, Australia,
and the U.S.
Although details vary from study to study, these acute HCV infections
have been linked to unprotected anal intercourse, fisting, multiple
sex partners, group sex, use of sex toys, nasal drug use, and presence
of other sexually transmitted diseases; coinfected men typically do
not report injection drug use.
Daniel Fierer from Mt. Sinai School of Medicine in New York City and
colleagues conducted a genetic analysis to see if cases of acute HCV
infection among HIV positive gay/bisexual men in the U.S. are genetically
related to the European and Australian cases.
In 2009, Thijs van de Laar and colleagues reported results
from a phylogenetic analysis indicating that HCV from coinfected
gay and bisexual men in Europe and Australia fell into clusters of related
viruses. More than 80% of European HCV strains and about 40% from Australia
belonged to 11 clusters, some of which included men from multiple countries.
These findings they wrote, "revealed a large international network
of HCV transmission among HIV positive MSM."
In the analysis presented at CROI, investigators looked at new HCV infections
among HIV positive MSM in 6 U.S. cities. They sequenced a 436 base pair
region of the HCV NS5B polymerase gene and constructed phylogenetic
trees to show the relationship among U.S. viral strains, and between
U.S. strains and those found in Europe and Australia.
accumulates mutations as it replicates, viral strains that are closer
to one another in a tree are more recently descended from a common ancestor;
degree of relationship, therefore, can reveal transmission patterns.
included 102 HCV sequences from men in the U.S. (77 from New York City,
12 from San Francisco, 9 from Boston, 2 from Philadelphia, and 1 each
from Los Angeles and San Diego), as well as 128 men in Europe and Australia.
All had hard-to-treat HCV genotype 1.
90% of U.S. HCV strains were genotype 1a and about 10% were genotype
of the U.S. men in this analysis had an unusual genotype 4 HCV strain
seen in European men.
strains could be grouped into 9 clusters, each representing 3 to
clusters were found among men in New York City.
than half the patients fell into at least 1 of these clusters.
were 8 pairs (2 person clusters) of homologous, or very similar,
of the U.S. men carried an HCV sequence that was very similar to
that found in at least 1 other man, usually from the same city.
was extensive clustering within cities, especially New York and
was limited clustering, however, between cities in the Northeast
was also limited clustering between East Coast and West Coast cities,
although there was a New York/San Diego pair and a New York/San
was minimal overlap between U.S. HCV sequences and those from Europe
or Australia, although 2 San Francisco strains fell into large European
epidemiology shows little overlap between U.S., European, and Australian
cities, suggesting largely independent evolution of epidemics, not a
network of transmission," the investigators concluded.
a few strains sweeping across countries, what we have is simultaneous
behavior clusters," Fierer said. "We need better prevention
affiliations: Mt Sinai School of Medicine, New York, NY; Centers for
Disease Control and Prevention, Atlanta, GA; Univ of California San
Francisco School of Medicine, San Francisco, CA; Weill Cornell Medical
College, New York, NY; Univ of Pennsylvania School of Medicine, Philadelphia,
PA; Univ of New South Wales, Sydney, Australia; VU Univ Medical Ctr,
Fierer, Y Khudyakov, B Hare, et al. Molecular Epidemiology of Incident
HCV Infection in HIV-infected MSM in the US vs Infections in Europe
and Australia. 18th Conference on Retroviruses and Opportunistic Infections
(CROI 2011). Boston. February 27-March 2, 2011. Abstract