Genomic Diversity of Haemophilus influenzae Serotype a in an Outbreak Community-Alaska, 2018.

BACKGROUND: Haemophilus influenzae serotype a (Hia) can cause severe invasive disease, especially in young children. In 2018, 4 invasive Hia cases occurred in an Alaska community. We used whole-genome sequencing (WGS) to evaluate the relationship of the bacteria from this community and other Alaska patients with invasive Hia. METHODS: All carriage (n = 15) and invasive (n = 4) Hia isolates from the outbreak community, together with 15 nonoutbreak Alaska invasive Hia surveillance isolates from 2018, were tested for antimicrobial susceptibility and characterized using WGS. RESULTS: Phylogenetic analysis of both invasive and carriage Hia isolates revealed 2 major clades that differed by an average of 300 core single-nucleotide polymorphisms (SNPs). All isolates from the outbreak community were clustered in 1 subclade, within a larger clade containing 3 nonoutbreak invasive Hia isolates. Comparative genomics did not reveal any genetic mutations that distinguished carriage from invasive isolates. Three (20%) community isolates were rifampin resistant and had a previously unreported mutation in the rpoB gene. CONCLUSIONS: In the outbreak community, Hia isolates from carriers were indistinguishable from the invasive Hia isolates. Overall, invasive Hia isolates from Alaska in 2018 were genetically similar. The rifampin resistance mutation is concerning as rifampin is the first-line medication for Hia prophylaxis.

Impact of Social Distancing and Travel Restrictions on Non-Coronavirus Disease 2019 (Non-COVID-19) Respiratory Hospital Admissions in Young Children in Rural Alaska.

Hospitalizations due to non-coronavirus disease 2019 (non-COVID-19) respiratory illnesses decreased dramatically after social distancing was implemented in a high-risk population in rural Alaska; an unprecedented decline compared to the past 10 respiratory seasons. This demonstrates the potential secondary benefits of implementing social distancing and travel restrictions on respiratory illnesses.

Haemophilus influenzae Serotype a (Hia) Carriage in a Small Alaska Community After a Cluster of Invasive Hia Disease, 2018.

BACKGROUND: Between May and July 2018, 4 Haemophilus influenzae serotype a (Hia) infections occurred in a remote Alaska community. We performed a public health response to prevent further illness and understand Hia carriage. METHODS: We collected oropharyngeal samples community-wide to evaluate baseline carriage. Risk factors were evaluated by interview. We offered prophylactic rifampin to individuals in contact with invasive Hia patients (contacts) and to all children aged <10 years. Oropharyngeal samples were collected again 8 weeks after rifampin distribution. Samples were tested using real-time polymerase chain reaction and culture. RESULTS: At baseline, 4 of 27 (14.8%) contacts and 7 of 364 (1.9%) noncontacts (P < .01) carried Hia. Contacts aged <10 years were more likely to carry Hia at any timepoint (11/18 [61%]) compared to contacts aged ≥10 years (3/34 [8.8%]), noncontacts aged <10 years (2/139 [1.4%]), and noncontacts ≥10 years (6/276 [2.2%]) (P < .001 for all). Hia carriers were clustered in 9 households (7% of total households). At the household level, carriage was associated with households with ≥1 contact (prevalence ratio [PR], 5.6 [95% confidence interval {CI}, 1.3-21.6]), crowding (PR, 7.7 [95% CI, 1.1-199.5]), and ≥3 tobacco users (PR, 5.0 [95% CI, 1.2-19.6]). Elevated carriage prevalence persisted in contacts compared to noncontacts 8 weeks after rifampin distribution (6/25 [24%] contacts, 2/114 [1.8%] noncontacts; P < .001). CONCLUSIONS: Hia carriage prevalence was significantly higher among contacts than noncontacts. Rifampin prophylaxis did not result in a reduction of Hia carriage prevalence in this community.

Characterizing wild bird contact and seropositivity to highly pathogenic avian influenza A (H5N1) virus in Alaskan residents.

BACKGROUND: Highly pathogenic avian influenza A (HPAI) H5N1 viruses have infected poultry and wild birds on three continents with more than 600 reported human cases (59% mortality) since 2003. Wild aquatic birds are the natural reservoir for avian influenza A viruses, and migratory birds have been documented with HPAI H5N1 virus infection. Since 2005, clade 2.2 HPAI H5N1 viruses have spread from Asia to many countries. OBJECTIVES: We conducted a cross-sectional seroepidemiological survey in Anchorage and western Alaska to identify possible behaviors associated with migratory bird exposure and measure seropositivity to HPAI H5N1. METHODS: We enrolled rural subsistence bird hunters and their families, urban sport hunters, wildlife biologists, and a comparison group without bird contact. We interviewed participants regarding their exposures to wild birds and collected blood to perform serologic testing for antibodies against a clade 2.2 HPAI H5N1 virus strain. RESULTS: Hunters and wildlife biologists reported exposures to wild migratory birds that may confer risk of infection with avian influenza A viruses, although none of the 916 participants had evidence of seropositivity to HPAI H5N1. CONCLUSIONS: We characterized wild bird contact among Alaskans and behaviors that may influence risk of infection with avian influenza A viruses. Such knowledge can inform surveillance and risk communication surrounding HPAI H5N1 and other influenza viruses in a population with exposure to wild birds at a crossroads of intercontinental migratory flyways.