Background Invasive group A Streptococcus (GAS) infections are associated with significant morbidity and mortality rates. We report the epidemiology and trends of invasive GAS over 8 years of surveillance. Methods From January 2005 through December 2012, we collected data from the Centers for Disease Control and Prevention’s Active Bacterial Core surveillance, a population-based network of 10 geographically diverse US sites (2012 population, 32.8 million). We defined invasive GAS as isolation of GAS from a normally sterile site or from a wound in a patient with necrotizing fasciitis (NF) or streptococcal toxic shock syndrome (STSS). Available isolates were emm typed. We calculated rates and made age- and race-adjusted national projections using census data. Results We identified 9557 cases (3.8 cases per 100 000 persons per year) with 1116 deaths (case-fatality rate, 11.7%). The case-fatality rates for septic shock, STSS, and NF were 45%, 38%, and 29%, respectively. The annual incidence was highest among persons aged ≥65 years (9.4/100 000) or <1 year (5.3) and among blacks (4.7/100 000). National rates remained steady over 8 years of surveillance. Factors independently associated with death included increasing age, residence in a nursing home, recent surgery, septic shock, NF, meningitis, isolated bacteremia, pneumonia, emm type 1 or 3, and underlying chronic illness or immunosuppression. An estimated 10 649–13 434 cases of invasive GAS infections occur in the United States annually, resulting in 1136–1607 deaths. In a 30-valent M-protein vaccine, emm types accounted for 91% of isolates. Conclusions The burden of invasive GAS infection in the United States remains substantial. Vaccines under development could have a considerable public health impact.

During 2000–2011, passive surveillance for legionellosis in the United States demonstrated a 249% increase in crude incidence, although little was known about the clinical course and method of diagnosis. In 2011, a system of active, population-based surveillance for legionellosis was instituted through CDC’s Active Bacterial Core surveillance (ABCs) program. Overall disease rates were similar in both the passive and active systems, but more complete demographic information and additional clinical and laboratory data were only available from ABCs. ABCs data during 2011–2013 showed that approximately 44% of patients with legionellosis required intensive care, and 9% died. Disease incidence was higher among blacks than whites and was 10 times higher in New York than California. Laboratory data indicated a reliance on urinary antigen testing, which only detects Legionella pneumophila serogroup 1 (Lp1). ABCs data highlight the severity of the disease, the need to better understand racial and regional differences, and the need for better diagnostic testing to detect infections.

Cross-reactivity within flavivirus antibody assays, produced by shared epitopes in the envelope proteins, can complicate the serological diagnosis of Zika virus (ZIKAV) infection. We assessed the utility of the plaque reduction neutralization test (PRNT) to confirm recent ZIKAV infections and rule out misleading positive immunoglobulin M (IgM) results in areas with various levels of past dengue virus (DENV) infection incidence. We reviewed PRNT results of sera collected for diagnosis of ZIKAV infection from 1 January through 31 August 2016 with positive ZIKAV IgM results, and ZIKAV and DENV PRNTs were performed. PRNT result interpretations included ZIKAV, unspecified flavivirus, DENV infection, or negative. For this analysis, ZIKAV IgM was considered false positive for samples interpreted as a DENV infection or negative. In U.S. states, 208 (27%) of 759 IgM-positive results were confirmed to be ZIKAV compared to 11 (21%) of 52 in the U.S. Virgin Islands (USVI), 15 (15%) of 103 in American Samoa, and 13 (11%) of 123 in Puerto Rico. In American Samoa and Puerto Rico, more than 80% of IgM-positive results were unspecified flavivirus infections. The false-positivity rate was 27% in U.S. states, 18% in the USVI, 2% in American Samoa, and 6% in Puerto Rico. In U.S. states, the PRNT provided a virus-specific diagnosis or ruled out infection in the majority of IgM-positive samples. Almost a third of ZIKAV IgM-positive results were not confirmed; therefore, providers and patients must understand that IgM results are preliminary. In territories with historically higher rates of DENV transmission, the PRNT usually could not differentiate between ZIKAV and DENV infections.

Background People experiencing homelessness are at increased risk of COVID-19, but little is known about specific risk factors for infection within homeless shelters. Methods We performed widespread SARS-CoV-2 PCR testing and collected risk factor information at all homeless shelters in Chicago with at least one reported case of COVID-19 (n=21). Multivariable, mixed-effects log-binomial models were built to estimate adjusted prevalence ratios (aPRs) for SARS-CoV-2 infection for both individual and facility-level risk factors. Results During March 1 to May 1, 2020, 1717 shelter residents and staff were tested for SARS-CoV-2; 472 (27%) persons tested positive. Prevalence of infection was higher for residents (431/1435, 30%) than for staff (41/282, 15%) (prevalence ratio [PR] =2.52, 95% CI 1.78–3.58). The majority of residents with SARS-CoV-2 infection (293/406 with available information about symptoms, 72%) reported no symptoms at the time of specimen collection or within the following two weeks.Among residents, sharing a room with a large number of people was associated with increased likelihood of infection (aPR for sharing with &gt;20 people compared to single rooms = 1.76, 95% CI 1.11–2.80), and current smoking was associated with reduced likelihood of infection (aPR=0.71, 95% CI 0.60–0.85). At the facility-level, a higher proportion of residents leaving and returning each day was associated with increased prevalence (aPR=1.08, 95% CI 1.01–1.16), while an increase in the number of private bathrooms was associated with reduced prevalence (aPR for one additional private bathroom per 100 people = 0.92, 95% CI 0.87–0.98). Conclusions We identified a high prevalence of SARS-CoV-2 infections in homeless shelters. Reducing the number of residents sharing dormitories might reduce the likelihood of SARS-CoV-2 infection. When community transmission is high, limiting movement of persons experiencing homelessness into and out of shelters might also be beneficial.