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We characterized 55 influenza A(H9N2) viruses isolated in Pakistan during 2014-2016 and found that the hemagglutinin gene is of the G1 lineage and that internal genes have differentiated into a variety of novel genotypes. Some isolates had up to 4-fold reduction in hemagglutination inhibition titers compared with older viruses. Viruses with hemagglutinin A180T/V substitutions conveyed this antigenic diversity and also caused up to 3,500-fold greater binding to avian-like and >20-fold greater binding to human-like sialic acid receptor analogs. This enhanced binding avidity led to reduced virus replication in primary and continuous cell culture. We confirmed that altered receptor-binding avidity of H9N2 viruses, including enhanced binding to human-like receptors, results in antigenic variation in avian influenza viruses. Consequently, current vaccine formulations might not induce adequate protective immunity in poultry, and emergence of isolates with marked avidity for human-like receptors increases the zoonotic risk.

We assessed consumption of raw pig blood, which is a risk factor for Streptococcus suis infection in Vietnam, by using a mix-method design. Factors associated with consumption included rural residency, age, sex, occupation, income, and marital status. We identified risk groups and practices and perceptions that should be targeted by communication programs.

To the Editor: Streptococcus suis, an opportunistic pathogen of swine, is an emerging zoonotic pathogen among humans (1). In Vietnam, S. suis is the leading cause of human acute bacterial meningitis (2). Infection in humans is associated with direct exposure to infected pigs or infected raw or undercooked pork products (3). Of the 35 S. suis serotypes, only a limited number are pathogenic for pigs, and clinical cases in humans have most frequently been attributed to serotype 2 (SS2) (1). In Vietnam during September 2006–November 2007, the carrier rate of S. suis among slaughterhouse pigs was 41% (222/542); SS2 was the most frequently identified serotype in 14% (45/317) of S. suis isolations (4). Porcine respiratory and reproductive syndrome (PRRS) is a major disease affecting the swine industry globally; the severity of PRRS in pigs can be increased by co-infection with S. suis (5). In 2010, PRRS outbreaks in swine were reported in 49 of 63 Vietnamese provinces (Technical Appendix Figure) (6). To understand the potential implications of swine PRRS outbreaks for human S. suis disease, we investigated co-infections of S. suis and PRRS virus (PRRSV) in sick pigs in 3 provinces of Vietnam during the PRRS outbreaks in 2010 (Technical Appendix Figure). We sampled 108 farms reporting pigs that had a clinical syndrome consistent with PRRSV infections in the provinces of Thai Binh (May), Tien Giang (July), and Soc Trang (July). Samples were blood from sick febrile pigs and postmortem tissue from freshly culled pigs. To confirm swine PRRS outbreaks, we performed reverse transcription real-time PCR on 1 randomly selected plasma sample from each farm (7). A total of 103 (95%) plasma samples from 103 farms tested positive for PRRSV (Chinese genotype). We additionally selected 3 PRRSV-positive farms per province for comprehensive PRRSV screening of all 42 sampled pigs; 100% of samples from the 9 farms were PRRSV positive. After swine outbreaks ended, blood samples from 52 healthy pigs from 10 farms that had no recent history of PRRS were collected from Tien Giang Province (March 2011). None of the 52 plasma samples from the 10 control farms tested positive for PRRSV. We investigated the presence of SS2 in blood and tissue samples from pigs on PRRS- and non-PRRS–affected farms by bacterial culture (Technical Appendix Table). A total of 534 specimens from sick pigs yielded 9 (1.7%) SS2 isolates. One (2%) of 52 specimens from the healthy control pigs yielded a non-SS2 S. suis isolate. S. suis has been proposed to contribute to the spread of antimicrobial resistance genes to other human pathogenic streptococci (8). The antimicrobial susceptibility results of 9 SS2 isolates by disk diffusion (9) revealed a high prevalence (6/9, 66%) of resistance to tetracycline, tobramycin, enrofloxacin, and either marbofloxacin or chloramphenicol. PCR amplification of the 16SrDNA gene (10) and the cps2J gene (2) was performed on all blood samples to detect S. suis and SS2, respectively. Ninety-two (18%) of 521 sick pigs from PRRSV outbreak farms were systemically infected with S. suis. In contrast, no healthy pigs from control farms were positive for S. suis by PCR (Technical Appendix Table). The SS2-cps2J–specific PCR was positive for 58 (11%) of 521 samples, and the S. suis-16SrDNA PCR was positive for 55 (11%). Twenty-one of the 16SrDNA-positive samples also were positive for cps2J-PCR, which indicated that 34 (7%) sick pigs were infected with non-SS2 strains. Therefore, SS2 accounted for most (58 [63%] of 92) S. suis–positive detections. The bacterial load of SS2 in blood ranged from 1 × 103 CFU/mL–1 to 8.3 × 106 CFU/mL–1 (median 9.2 × 103 CFU/mL–1). Overall, SS2 was found in 58 (11%) sick pigs and on 33 (32%) PRRS outbreak farms. The higher prevalence (92 [18%]) of systemic infections of S. suis and SS2 with high bacterial load in pigs from PRRS outbreak farms compared with prevalence on nonoutbreak farms (1 [2%] of 52) suggests increased systemic S. suis infections during swine PRRS outbreaks (p = 0.001, Fisher exact test). We investigated the possible association between swine PRRS outbreaks and human S. suis infection. Case reports of confirmed human infections during 2007–2010 at the 2 tertiary referral hospitals in Hanoi and Ho Chi Minh City were reviewed. The number of human S. suis infection cases increased in August 2010 in southern Vietnam and doubled in northern Vietnam during May–August and October–November 2010 (Figure). Swine PRRS outbreaks were reported during June–September and March–December 2010 in southern and northern provinces, respectively (6) (Technical Appendix Figure). Most patients with S. suis infection during these periods resided in provinces reporting swine PRRS outbreaks. Our data suggest a possible temporal association between swine PRRS outbreaks and human S. suis infections. Figure Monthly distribution of human Streptococcus suis infections in 2 referral hospitals, Vietnam, 2007–2010. Humans infected with S. suis during 2007–2009 are presented as mean total cases per month. Dark gray and black bars represent the ... We demonstrated increased prevalence of systemic S. suis and SS2 infection in pigs co-infected with PRRSV during the 2010 swine outbreaks in Vietnam. The results indicate an increased risk for potential zoonotic transmission of S. suis to humans during outbreaks of PRRS in swine. Technical Appendix: Systemic Streptococcus suis infections in sick pigs from farms with confirmed porcine reproductive and respiratory syndrome and temporal distribution of outbreaks of porcine reproductive and respiratory syndrome in swine, 3 provinces, Vietnam, 2010. Click here to view.(151K, pdf)

The prevailing paradigm of yellow fever virus (YFV) ecology in South America is that of wandering epizootics. The virus is believed to move from place to place in epizootic waves involving monkeys and mosquitoes, rather than persistently circulating within particular locales. After a large outbreak of YFV illness in Peru in 1995, we used phylogenetic analyses of virus isolates to reexamine the hypothesis of virus movement. We sequenced a 670-nucleotide fragment of the prM/E gene region of from 25 Peruvian YFV samples collected from 1977 to 1999, and delineated six clades representing the states (Departments) of Puno, Pasco, Junin, Ayacucho, San Martin/Huanuco, and Cusco. The concurrent appearance of at least four variants during the 1995 epidemic and the genetic stability of separate virus lineages over time, indicate that Peruvian YFV is locally maintained and circulates continuously in discrete foci of enzootic transmission.

A novel protein translocation system, the type-6 secretion system (T6SS), may play a role in virulence of Campylobacter jejuni. We investigated 181 C. jejuni isolates from humans, chickens, and environmental sources in Vietnam, Thailand, Pakistan, and the United Kingdom for T6SS. The marker was most prevalent in human and chicken isolates from Vietnam.

To the Editor: To investigate bats as potential reservoirs for Bartonella spp. in Vietnam, we screened a range of bat species to determine the prevalence and genetic diversity of Bartonella spp. in bat populations in southern Vietnam. In a study of bat biodiversity in southern Vietnam, 60 bats were trapped at 6 sites in Dong Nai Culture and Nature Reserve and Cat Tien National Park, Vietnam, in May 2013. Bats were trapped by using mist nets and harp traps set at ground level, and were euthanized by using isoflurane (http://www.avma.org/KB/Policies/Documents/euthanasia.pdf) for cataloguing at the Vietnam Academy of Sciences and Technology, Hanoi. Blood specimens were collected by cardiac puncture, and external measurements were recorded. Bats were speciated according to morphology (1,2); trapped bats represented 10 species belonging to 5 genera. All species have been given a conservation status of least concern (http://www.iucnredlist.org/). Total nucleic acid was extracted from blood samples by using the MagNApure automated nucleic acid extraction system (Roche, Basel, Switzerland). Extracted nucleic acid was subjected to conventional PCR to detect Bartonella spp. DNA by using primers specific for the citrate synthase A gene (3). A positive PCR result was determined by amplification of a 729-bp fragment. Twenty-one (35.0%) of 60 bat blood specimens had a result consistent with presence of Bartonella spp. (Table). Among insectivorous or carnivorous bats, Bartonella prevalence was 20 (45.5%) of 44 compared with 1 (6.2%) of 16 fruit-eating bats (χ2 = 6.3, p = 0.01). The prevalence of Bartonella spp. did not differ between sampling locations (Table) or by estimated age of the bat (determined by deviation above or below the median tibial length of each species); prevalence was 33.3% (9/27) in younger bats and 36.4% (12/33) in older bats. Table Prevalence of Bartonella spp. in bats from 2 sites in Dong Nai, Vietnam, 2013 DNA sequences from the 21 PCR citrate synthase A gene amplicons (GenBank accession nos. {"type":"entrez-nucleotide-range","attrs":{"text":"KP100340-KP100360","start_term":"KP100340","end_term":"KP100360","start_term_id":"766544325","end_term_id":"766544365"}}KP100340-KP100360) were subjected to BLAST analysis (http://blast.ncbi.nlm.nih.gov/Blast.cgi) to assess sequence similarity. Potentially novel Bartonella phylogroups were identified as having 80% support. Taxa names for sequences determined in this study are indicated in bold italics, phylogroups are indicated in parentheses (I–X), and bat species are indicated after phylogroups. Click here to view.(202K, pdf)

Examining viral isolates collected over 66 years shows divergence into clades and potential dispersal by human migration., An analysis of 79 yellow fever virus (YFV) isolates collected from 1935 to 2001 in Brazil showed a single genotype (South America I) circulating in the country, with the exception of a single strain from Rondônia, which represented South America genotype II. Brazilian YFV strains have diverged into two clades; an older clade appears to have become extinct and another has become the dominant lineage in recent years. Pairwise nucleotide diversity between strains ranged from 0% to 7.4%, while amino acid divergence ranged from 0% to 4.6%. Phylogenetic analysis indicated traffic of virus variants through large geographic areas and suggested that migration of infected people may be an important mechanism of virus dispersal. Isolation of vaccine virus from a patient with a fatal case suggests that vaccine-related illness may have been misdiagnosed in the past.