Case investigation and contact tracing (CICT) are public health measures that aim to break the chain of pathogen transmission. Changes in viral characteristics of COVID-19 variants have likely affected the effectiveness of CICT programs. We estimated and compared the cases averted in Vermont when the original COVID-19 strain circulated (Nov. 25, 2020-Jan. 19, 2021) with two periods when the Delta strain dominated (Aug. 1-Sept. 25, 2021, and Sept. 26-Nov. 20, 2021). When the original strain circulated, we estimated that CICT prevented 7180 cases (55% reduction in disease burden), compared to 1437 (15% reduction) and 9970 cases (40% reduction) when the Delta strain circulated. Despite the Delta variant being more infectious and having a shorter latency period, CICT remained an effective tool to slow spread of COVID-19; while these viral characteristics did diminish CICT effectiveness, non-viral characteristics had a much greater impact on CICT effectiveness.

Vermont contact tracing (CT) consistently identified people at risk for COVID-19. However, the prevalence ratio (PR) of COVID-19 among contacts compared with noncontacts when viral transmission was high (PR = 13.5; 95% CI: 13.2-13.9) was significantly less than when transmission was low (PR = 49.3; 95% CI: 43.2-56.3).

Vaccination protects against infection with SARS-CoV-2 (the virus that causes COVID-19) and related hospitalizations (1,2), and surviving a previous infection protects against B.1.1.7 (Alpha) and B.1.617.2 (Delta) variant reinfections† (2). Since the SARS-CoV-2 B.1.1.529 (Omicron) variant became predominant in the United States in late December 2021, reported reinfections have increased§ (3). Early reinfections (those occurring within 90 days of previous infection) are not well understood (4). Because some persons have prolonged detection of viral RNA after infection,¶ repeat positive nucleic acid amplification test (NAAT) results within 90 days could reflect prolonged shedding from earlier infection, presenting technical challenges to documenting and characterizing early reinfections. This report describes 10 patients from four states, with whole genome sequencing (WGS)–confirmed Omicron variant infections within 90 days of a previous Delta infection. This activity was reviewed by CDC, approved by respective institutional review boards, and was conducted consistent with applicable federal law and CDC policy.**

Human granulocytic anaplasmosis is an acute febrile tick-borne illness caused by the bacterium Anaplasma phagocytophilum. An anaplasmosis-related fatality in a Vermont resident with multiple comorbidities is described. Clinicians should be aware of the risk factors for severe outcomes of this emerging disease and promptly treat when suspected.

On August 11, 2020, a confirmed case of coronavirus disease 2019 (COVID-19) in a male correctional facility employee (correctional officer) aged 20 years was reported to the Vermont Department of Health (VDH). On July 28, the correctional officer had multiple brief encounters with six incarcerated or detained persons (IDPs)* while their SARS-CoV-2 test results were pending. The six asymptomatic IDPs arrived from an out-of-state correctional facility on July 28 and were housed in a quarantine unit. In accordance with Vermont Department of Corrections (VDOC) policy for state prisons, nasopharyngeal swabs were collected from the six IDPs on their arrival date and tested for SARS-CoV-2, the virus that causes COVID-19, at the Vermont Department of Health Laboratory, using real-time reverse transcription-polymerase chain reaction (RT-PCR). On July 29, all six IDPs received positive test results. VDH and VDOC conducted a contact tracing investigation(†) and used video surveillance footage to determine that the correctional officer did not meet VDH's definition of close contact (i.e., being within 6 feet of infectious persons for ≥15 consecutive minutes)(§)(,)(¶); therefore, he continued to work. At the end of his shift on August 4, he experienced loss of smell and taste, myalgia, runny nose, cough, shortness of breath, headache, loss of appetite, and gastrointestinal symptoms; beginning August 5, he stayed home from work. An August 5 nasopharyngeal specimen tested for SARS-CoV-2 by real-time RT-PCR at a commercial laboratory was reported as positive on August 11; the correctional officer identified two contacts outside of work, neither of whom developed COVID-19. On July 28, seven days preceding his illness onset, the correctional officer had multiple brief exposures to six IDPs who later tested positive for SARS-CoV-2; available data suggests that at least one of the asymptomatic IDPs transmitted SARS-CoV-2 during these brief encounters.

Background: Lyme disease is the most common vector-borne disease in the United States, and it is hyperendemic in the Northeast (1). In the United States, the spirochete Borrelia burgdorferi causes Lyme disease and is transmitted by the bite of an infected black-legged tick. Carditis is a rare manifestation that can usually be treated successfully with a short course of antibiotics (2). However, it can present with many symptoms, and its severity can change rapidly and unpredictably (3). Death can occur when Lyme carditis is untreated. Before this report, only 9 fatal cases were reported in the literature (4, 5). | | Objective: To remind clinicians of the importance of early recognition and treatment of Lyme carditis.

On October 22, 2018, the Vermont Department of Health (VDH) notified CDC’s Waterborne Disease Prevention Branch of an outbreak of diarrhea caused by Shigella sonnei among residents, visitors, and staff members of a retirement community in Chittenden County, the state’s most populous county. High-quality single nucleotide polymorphism (SNP) analysis predicted initial isolates were multidrug resistant (MDR), and were closely related to a concurrent multistate cluster (differing by 0–11 SNPs). In the United States, rates of MDR shigellosis are increasing (1); outbreaks of MDR shigellosis are more common among men who have sex with men and are rare in retirement community settings (2). CDC collaborated with VDH to identify additional cases, determine transmission routes, and recommend prevention and control measures.

Influenza viruses mutate frequently, necessitating constant updates of vaccine viruses. To establish experimental approaches that may complement the current vaccine strain selection process, we selected antigenic variants from human H1N1 and H3N2 influenza virus libraries possessing random mutations in the globular head of the haemagglutinin protein (which includes the antigenic sites) by incubating them with human and/or ferret convalescent sera to human H1N1 and H3N2 viruses. We also selected antigenic escape variants from human viruses treated with convalescent sera and from mice that had been previously immunized against human influenza viruses. Our pilot studies with past influenza viruses identified escape mutants that were antigenically similar to variants that emerged in nature, establishing the feasibility of our approach. Our studies with contemporary human influenza viruses identified escape mutants before they caused an epidemic in 2014-2015. This approach may aid in the prediction of potential antigenic escape variants and the selection of future vaccine candidates before they become widespread in nature.

BACKGROUND: In the United States, the proportion of Bordetella pertussis isolates lacking pertactin, a component of acellular pertussis vaccines, increased from 14% in 2010 to 85% in 2012. The impact on vaccine effectiveness (VE) is unknown. METHODS: We conducted 2 matched case-control evaluations in Vermont to assess VE of the 5-dose diphtheria, tetanus, and acellular pertussis vaccine (DTaP) series among 4- to 10-year-olds, and tetanus, diphtheria, and acellular pertussis vaccine (Tdap) among 11- to 19-year-olds. Cases reported during 2011 to 2013 were included. Three controls were matched to each case by medical home, and additionally by birth year for the Tdap evaluation. Vaccination history was obtained from medical records and parent interviews. Odds ratios (OR) were calculated by using conditional logistic regression; VE was estimated as (1-OR) x 100%. Pertactin status was determined for cases with available isolates. RESULTS: Overall DTaP VE was 84% (95% confidence interval [CI] 58%-94%). VE within 12 months of dose 5 was 90% (95% CI 71%-97%), declining to 68% (95% CI 10%-88%) by 5-7 years post-vaccination. Overall Tdap VE was 70% (95% CI 54%-81%). Within 12 months of Tdap vaccination, VE was 76% (95% CI 60%-85%), declining to 56% (95% CI 16%-77%) by 2-4 years post-vaccination. Of cases with available isolates, >90% were pertactin-deficient. CONCLUSIONS: Our DTaP and Tdap VE estimates remain similar to those found in other settings, despite high prevalence of pertactin deficiency in Vermont, suggesting these vaccines continue to be protective against reported pertussis disease.

Understanding the spatiotemporal patterns of emergence and circulation of new human seasonal influenza virus variants is a key scientific and public health challenge. The global circulation patterns of influenza A/H3N2 viruses are well characterized, but the patterns of A/H1N1 and B viruses have remained largely unexplored. Here we show that the global circulation patterns of A/H1N1 (up to 2009), B/Victoria, and B/Yamagata viruses differ substantially from those of A/H3N2 viruses, on the basis of analyses of 9,604 haemagglutinin sequences of human seasonal influenza viruses from 2000 to 2012. Whereas genetic variants of A/H3N2 viruses did not persist locally between epidemics and were reseeded from East and Southeast Asia, genetic variants of A/H1N1 and B viruses persisted across several seasons and exhibited complex global dynamics with East and Southeast Asia playing a limited role in disseminating new variants. The less frequent global movement of influenza A/H1N1 and B viruses coincided with slower rates of antigenic evolution, lower ages of infection, and smaller, less frequent epidemics compared to A/H3N2 viruses. Detailed epidemic models support differences in age of infection, combined with the less frequent travel of children, as probable drivers of the differences in the patterns of global circulation, suggesting a complex interaction between virus evolution, epidemiology, and human behaviour.

BACKGROUND: The Cambodian National Influenza Center (NIC) monitored and characterized circulating influenza strains from 2009 to 2011. METHODOLOGY/PRINCIPAL FINDINGS: Sentinel and study sites collected nasopharyngeal specimens for diagnostic detection, virus isolation, antigenic characterization, sequencing and antiviral susceptibility analysis from patients who fulfilled case definitions for influenza-like illness, acute lower respiratory infections and event-based surveillance. Each year in Cambodia, influenza viruses were detected mainly from June to November, during the rainy season. Antigenic analysis show that A/H1N1pdm09 isolates belonged to the A/California/7/2009-like group. Circulating A/H3N2 strains were A/Brisbane/10/2007-like in 2009 before drifting to A/Perth/16/2009-like in 2010 and 2011. The Cambodian influenza B isolates from 2009 to 2011 all belonged to the B/Victoria lineage represented by the vaccine strains B/Brisbane/60/2008 and B/Malaysia/2506/2004. Sequences of the M2 gene obtained from representative 2009-2011 A/H3N2 and A/H1N1pdm09 strains all contained the S31N mutation associated with adamantanes resistance except for one A/H1N1pdm09 strain isolated in 2011 that lacked this mutation. No reduction in the susceptibility to neuraminidase inhibitors was observed among the influenza viruses circulating from 2009 to 2011. Phylogenetic analysis revealed that A/H3N2 strains clustered each year to a distinct group while most A/H1N1pdm09 isolates belonged to the S203T clade. CONCLUSIONS/SIGNIFICANCE: In Cambodia, from 2009 to 2011, influenza activity occurred throughout the year with peak seasonality during the rainy season from June to November. Seasonal influenza epidemics were due to multiple genetically distinct viruses, even though all of the isolates were antigenically similar to the reference vaccine strains. The drug susceptibility profile of Cambodian influenza strains revealed that neuraminidase inhibitors would be the drug of choice for influenza treatment and chemoprophylaxis in Cambodia, as adamantanes are no longer expected to be effective.

In February and September each year the World Health Organisation (WHO) recommends influenza viruses to be included in influenza vaccines for the forthcoming winters in the Northern and Southern Hemispheres respectively. These recommendations are based on data collected by National Influenza Centres (NIC) through the Global Influenza Surveillance and Response System (GISRS) and a more detailed analysis of representative and potential antigenically variant influenza viruses from the WHO Collaborating Centres for Influenza (WHO CCs) and Essential Regulatory Laboratories (ERLs). This article provides a detailed summary of the antigenic and genetic properties of viruses and additional background data used by WHO experts during development of the recommendations for the 2012 Southern Hemisphere influenza vaccine composition.

BACKGROUND: During December 2006 to March 2007, a substantial increase in norovirus illnesses was noted in northern New England. We sought to identify institutional risk factors for norovirus outbreaks in northern New England long-term care facilities (LTCFs). METHODS: State health departments in Maine, New Hampshire, and Vermont distributed surveys to infection preventionists at all LTCFs in their respective states. We collected information regarding facility attributes, routine staff use of alcohol-based hand sanitizer (ABHS) versus soap and water, facility cleaning practices, and occurrence of any acute gastroenteritis outbreaks during December 2006 to March 2007. Norovirus confirmation was conducted in public health laboratories. Data were analyzed with univariate and logistic regression methods. RESULTS: Of 160 facilities, 91 (60%) provided survey responses, with 61 facilities reporting 73 outbreaks; 29 were confirmed norovirus. Facilities reporting that staff were equally or more likely to use ABHS than soap and water for routine hand hygiene had higher odds of an outbreak than facilities with staff less likely to use ABHS (adjusted odds ratio, 6.06; 95% confidence interval: 1.44-33.99). CONCLUSION: This study suggests that preferential use of ABHS over soap and water for routine hand hygiene might be associated with increased risk of norovirus outbreaks in LTCFs.

Influenza vaccines form an important component of the global response against infections and subsequent illness caused in man by influenza viruses. Twice a year, in February and September, the World Health Organisation through its Global Influenza Surveillance Network (GISN), recommends appropriate influenza viruses to be included in the seasonal influenza vaccine for the upcoming Northern and Southern Hemisphere winters. This recommendation is based on the latest data generated from many sources and the availability of viruses that are suitable for vaccine manufacture. This article gives a summary of the data and background to the recommendations for the 2009-2010 Northern Hemisphere influenza vaccine formulation.