Marc Fischer

Background: Adults aged ≥65 years, adults with certain underlying medical conditions, and persons experiencing homelessness are at increased risk for invasive pneumococcal disease (IPD). Two new pneumococcal conjugate vaccines, 15-valent pneumococcal conjugate vaccine (PCV15) and 20-valent pneumococcal conjugate vaccine (PCV20), were recently approved for use in US adults. We describe the epidemiology of IPD among Alaska adults and estimate the proportion of IPD cases potentially preventable by new vaccines. Methods: We used statewide, laboratory-based surveillance data to calculate and compare IPD incidence rates and 95% confidence intervals (CIs) among Alaska adults aged ≥18 years during 2011–2020 and estimate the proportion of IPD cases that were caused by serotypes in PCV15 and PCV20. Results: During 2011–2020, 1164 IPD cases were reported among Alaska adults for an average annual incidence of 21.3 cases per 100 000 adults per year (95% CI, 20.1–22.5). Incidence increased significantly during the study period (P < .01). IPD incidence among Alaska Native adults was 4.7 times higher than among non-Alaska Native adults (95% CI, 4.2–5.2). Among adults experiencing homelessness in Anchorage, IPD incidence was 72 times higher than in the general adult population (95% CI, 59–89). Overall, 1032 (89%) Alaska adults with IPD had an indication for pneumococcal vaccine according to updated vaccination guidelines; 456 (39%) and 700 (60%) cases were caused by serotypes in PCV15 and PCV20, respectively. Conclusions: Use of PCV15 and PCV20 could substantially reduce IPD among adults in Alaska, including Alaska Native adults and adults experiencing homelessness.

As of April 30, 2021, approximately 101 million people in the U.S. had been fully vaccinated against COVID-19. Almost 10,300 COVID-19 vaccine breakthrough infections were reported from 46 states and territories. Vaccine breakthrough infections occur in only a small fraction of all vaccinated people.

Laboratory-based surveillance for arboviral diseases is challenging in resource-limited settings. We evaluated the use of filter paper–dried sera for detection of dengue virus (DENV) RNA during an outbreak in American Samoa. Matched liquid and filter paper–dried sera were collected from patients with suspected dengue and shipped to a reference laboratory for diagnostic testing. RNA was extracted from each sample and tested for DENV RNA by real-time reverse transcription-polymerase chain reaction (RT-PCR). Of 18 RT-PCR–positive liquid specimens, 14 matched filter paper–dried specimens were positive for a sensitivity of 78% (95% CI, 55–91%). Of 82 RT-PCR–negative liquid specimens, all filter paper–dried specimens were negative for a specificity of 100% (95% CI, 96–100%). Shipping of filter paper–dried specimens was similarly timely but less expensive than shipping liquid sera. Using filter paper–dried serum or blood can be a cost-effective and sustainable approach to surveillance of dengue and other arboviral diseases in resource-limited settings.

St. Louis encephalitis virus (SLEV), an arthropod-borne flavivirus, can cause disease presentations ranging from mild febrile illness through severe encephalitis. We reviewed U.S. national SLEV surveillance data for 2003 through 2017, including human disease cases and nonhuman infections. Over the 15-year period, 198 counties from 33 states and the District of Columbia reported SLEV activity; 94 (47%) of those counties reported SLEV activity only in nonhuman species. A total of 193 human cases of SLEV disease were reported, including 148 cases of neuroinvasive disease. A median of 10 cases were reported per year. The national average annual incidence of reported neuroinvasive disease cases was 0.03 per million. States with the highest average annual incidence of reported neuroinvasive disease cases were Arkansas, Arizona, and Mississippi. No large outbreaks occurred during the reporting period. The most commonly reported clinical syndromes were encephalitis (N = 116, 60%), febrile illness (N = 35, 18%), and meningitis (N = 25, 13%). Median age of cases was 57 years (range 2–89 years). The case fatality rate was 6% (11/193) and all deaths were among patients aged > 45 years with neuroinvasive disease. Nonhuman surveillance data indicated wider SLEV activity in California, Nevada, and Florida than the human data alone suggested. Prevention depends on community efforts to reduce mosquito populations and personal protective measures to decrease exposure to mosquitoes.

Chikungunya virus is a mosquito-borne alphavirus that causes an acute febrile illness with severe polyarthralgia. The first local transmission of chikungunya virus in the Western Hemisphere was reported in December 2013. In the following year, the virus spread throughout much of the Americas and the number of cases among travelers increased substantially. We reviewed the epidemiology of chikungunya virus disease cases reported among U.S. travelers from 2014 to 2016. A total of 3,941 travel-acquired cases were reported from 49 states and the District of Columbia; 3,616 (92%) reported travel to other countries or territories in the Americas; the remaining 8% reported travel to Asia, Africa, or the Western Pacific. The most commonly reported travel destinations were the Dominican Republic, Puerto Rico, and Haiti. The largest number of cases (N = 2,780, 71%) had illness onset in 2014, followed by 2015 (N = 913, 23%) and 2016 (N = 248, 6%). Cases occurred in every month, but 70% of case-patients had illness onset from April to September, the months when mosquitoes are most likely to be active in the continental United States. Travel-acquired chikungunya cases will likely continue to occur and present a risk of introduction of the virus to locations in the continental United States. Clinicians and public health officials should be educated about the recognition, diagnosis, management, and timely reporting of chikungunya cases.

Numerous Zika virus vaccines are being developed. However, identifying sites to evaluate the efficacy of a Zika virus vaccine is challenging due to the general decrease in Zika virus activity. We compare results from three different modeling approaches to estimate areas that may have increased relative risk of Zika virus transmission during 2017. The analysis focused on eight priority countries (i.e., Brazil, Colombia, Costa Rica, Dominican Republic, Ecuador, Mexico, Panama, and Peru). The models projected low incidence rates during 2017 for all locations in the priority countries but identified several subnational areas that may have increased relative risk of Zika virus transmission in 2017. Given the projected low incidence of disease, the total number of participants, number of study sites, or duration of study follow-up may need to be increased to meet the efficacy study endpoints.

Zika virus is a mosquito-borne flavivirus that was first identified in Uganda in 1947 (1). Before 2007, only sporadic human disease cases were reported from countries in Africa and Asia. In 2007, the first documented outbreak of Zika virus disease was reported in Yap State, Federated States of Micronesia; 73% of the population aged ≥3 years is estimated to have been infected (2). Subsequent outbreaks occurred in Southeast Asia and the Western Pacific (3). In May 2015, the World Health Organization reported the first local transmission of Zika virus in the Region of the Americas (Americas), with autochthonous cases identified in Brazil (4). In December, the Ministry of Health estimated that 440,000-1,300,000 suspected cases of Zika virus disease had occurred in Brazil in 2015 (5). By January 20, 2016, locally-transmitted cases had been reported to the Pan American Health Organization from Puerto Rico and 19 other countries or territories in the Americas* (Figure) (6). Further spread to other countries in the region is being monitored closely.