To understand how coronavirus disease 2019 vaccines impact infection risk in children <5 years, we assessed risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection from September 2022 to April 2023 in 3 cohort studies. There was no difference in risk by vaccination status. While vaccines reduce severe disease, they may not reduce SARS-CoV-2 infections in naïve young children.

BACKGROUND: Cruise travel contributed to SARS-CoV-2 transmission when there were relatively few cases in the United States. By March 14, 2020, the Centers for Disease Control and Prevention (CDC) issued a No Sail Order suspending U.S. cruise operations; the last U.S. passenger ship docked on April 16. METHODS: We analyzed SARS-CoV-2 outbreaks on cruises in U.S. waters or carrying U.S. citizens and used regression models to compare voyage characteristics. We used compartmental models to simulate the potential impact of four interventions (screening for COVID-19 symptoms; viral testing on two days and isolation of positive persons; reduction of passengers by 40%, crew by 20%, and port visits to one) for 7-day and 14-day voyages. RESULTS: During January 19-April 16, 2020, 89 voyages on 70 ships had known SARS-CoV-2 outbreaks; 16 ships had recurrent outbreaks. There were 1,669 RT-PCR-confirmed SARS-CoV-2 infections and 29 confirmed deaths. Longer voyages were associated with more cases (adjusted incidence rate ratio, 1.10, 95% CI: 1.03-1.17, p < 0.0001). Mathematical models showed that 7-day voyages had about 70% fewer cases than 14-day voyages. On 7-day voyages, the most effective interventions were reducing the number of individuals onboard (43-49% reduction in total infections) and testing passengers and crew (42-43% reduction in total infections). All four interventions reduced transmission by 80%, but no single intervention or combination eliminated transmission. Results were similar for 14-day voyages. CONCLUSIONS: SARS-CoV-2 outbreaks on cruises were common during January-April 2020. Despite all interventions modeled, cruise travel still poses a significant SARS-CoV-2 transmission risk.

IMPORTANCE: Case-based surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection likely underestimates the true prevalence of infections. Large-scale seroprevalence surveys can better estimate infection across many geographic regions. OBJECTIVE: To estimate the prevalence of persons with SARS-CoV-2 antibodies using residual sera from commercial laboratories across the US and assess changes over time. DESIGN, SETTING, AND PARTICIPANTS: This repeated, cross-sectional study conducted across all 50 states, the District of Columbia, and Puerto Rico used a convenience sample of residual serum specimens provided by persons of all ages that were originally submitted for routine screening or clinical management from 2 private clinical commercial laboratories. Samples were obtained during 4 collection periods: July 27 to August 13, August 10 to August 27, August 24 to September 10, and September 7 to September 24, 2020. EXPOSURES: Infection with SARS-CoV-2. MAIN OUTCOMES AND MEASURES: The proportion of persons previously infected with SARS-CoV-2 as measured by the presence of antibodies to SARS-CoV-2 by 1 of 3 chemiluminescent immunoassays. Iterative poststratification was used to adjust seroprevalence estimates to the demographic profile and urbanicity of each jurisdiction. Seroprevalence was estimated by jurisdiction, sex, age group (0-17, 18-49, 50-64, and ≥65 years), and metropolitan/nonmetropolitan status. RESULTS: Of 177 919 serum samples tested, 103 771 (58.3%) were from women, 26 716 (15.0%) from persons 17 years or younger, 47 513 (26.7%) from persons 65 years or older, and 26 290 (14.8%) from individuals living in nonmetropolitan areas. Jurisdiction-level seroprevalence over 4 collection periods ranged from less than 1% to 23%. In 42 of 49 jurisdictions with sufficient samples to estimate seroprevalence across all periods, fewer than 10% of people had detectable SARS-CoV-2 antibodies. Seroprevalence estimates varied between sexes, across age groups, and between metropolitan/nonmetropolitan areas. Changes from period 1 to 4 were less than 7 percentage points in all jurisdictions and varied across sites. CONCLUSIONS AND RELEVANCE: This cross-sectional study found that as of September 2020, most persons in the US did not have serologic evidence of previous SARS-CoV-2 infection, although prevalence varied widely by jurisdiction. Biweekly nationwide testing of commercial clinical laboratory sera can play an important role in helping track the spread of SARS-CoV-2 in the US.

As of September 21, 2020, the coronavirus disease 2019 (COVID-19) pandemic had resulted in 6,786,352 cases and 199,024 deaths in the United States.* Health care personnel (HCP) are essential workers at risk for exposure to patients or infectious materials (1). The impact of COVID-19 on U.S. HCP was first described using national case surveillance data in April 2020 (2). Since then, the number of reported HCP with COVID-19 has increased tenfold. This update describes demographic characteristics, underlying medical conditions, hospitalizations, and intensive care unit (ICU) admissions, stratified by vital status, among 100,570 HCP with COVID-19 reported to CDC during February 12-July 16, 2020. HCP occupation type and job setting are newly reported. HCP status was available for 571,708 (22%) of 2,633,585 cases reported to CDC. Most HCP with COVID-19 were female (79%), aged 16-44 years (57%), not hospitalized (92%), and lacked all 10 underlying medical conditions specified on the case report form(†) (56%). Of HCP with COVID-19, 641 died. Compared with nonfatal COVID-19 HCP cases, a higher percentage of fatal cases occurred in males (38% versus 22%), persons aged ≥65 years (44% versus 4%), non-Hispanic Asians (Asians) (20% versus 9%), non-Hispanic Blacks (Blacks) (32% versus 25%), and persons with any of the 10 underlying medical conditions specified on the case report form (92% versus 41%). From a subset of jurisdictions reporting occupation type or job setting for HCP with COVID-19, nurses were the most frequently identified single occupation type (30%), and nursing and residential care facilities were the most common job setting (67%). Ensuring access to personal protective equipment (PPE) and training, and practices such as universal use of face masks at work, wearing masks in the community, and observing social distancing remain critical strategies to protect HCP and those they serve.

Insecticide resistance across sub-Saharan Africa may impact the continued effectiveness of malaria vector control. We investigated the association between carbamate and pyrethroid resistance with Anopheles gambiae s.l. parity, Plasmodium falciparum infection, and molecular insecticide resistance mechanisms in Guinea. Pyrethroid resistance was intense, with field populations surviving ten times the insecticidal concentration required to kill susceptible individuals. The L1014F kdr-N1575Y haplotype and I1527T mutation were significantly associated with mosquito survival following permethrin exposure (Prevalence Ratio; PR = 1.92, CI = 1.09-3.37 and PR = 2.80, CI = 1.03-7.64, respectively). Partial restoration of pyrethroid susceptibility following synergist pre-exposure suggests a role for mixed-function oxidases. Carbamate resistance was lower and significantly associated with the G119S Ace-1 mutation. Oocyst rates were 6.8% and 4.2% among resistant and susceptible mosquitoes, respectively; survivors of bendiocarb exposure were significantly more likely to be infected. Pyrethroid resistant mosquitoes had significantly lower parity rates than their susceptible counterparts (PR = 1.15, CI = 1.10-1.21). Our findings emphasize the need for additional studies directly assessing the influence of insecticide resistance on mosquito fitness.

Cyclospora cayetanensis is a coccidian parasite associated with diarrheal illness. In the USA, foodborne outbreaks of cyclosporiasis have been documented almost every year since the mid-1990s. The typical approach used to identify this parasite in human stools is an examination of acid-fast-stained smears under bright-field microscopy. UV fluorescence microscopy of wet mounts is more sensitive and specific than acid-fast staining but requires a fluorescence microscope with a special filter not commonly available in diagnostic laboratories. In this study, we evaluated a new DNA extraction method based on the Universal Nucleic Acid Extraction (UNEX) buffer and compared the performances of four published real-time polymerase chain reaction (PCR) assays for the specific detection of C. cayetanensis in stool. The UNEX-based method had an improved capability to recover DNA from oocysts compared with the FastDNA stool extraction method. The best-performing real-time PCR assay was a C. cayetanensis-specific TaqMan PCR that targets the 18S ribosomal RNA gene. This new testing algorithm should be useful for detection of C. cayetanensis in human stool samples.

BACKGROUND: Although malaria control intervention has greatly decreased malaria morbidity and mortality in many African countries, further decline in parasite prevalence has stagnated in western Kenya. In order to assess if malaria transmission reservoir is associated with this stagnation, submicroscopic infection and gametocyte carriage was estimated. Risk factors and associations between malaria control interventions and gametocyte carriage were further investigated in this study. METHODS: A total of 996 dried blood spot samples were used from two strata, all smear-positives (516 samples) and randomly selected smear-negatives (480 samples), from a community cross-sectional survey conducted at peak transmission season in 2012 in Siaya County, western Kenya. Plasmodium falciparum parasite presence and density were determined by stained blood smear and by 18S mRNA transcripts using nucleic acid sequence-based amplification assay (NASBA), gametocyte presence and density were determined by blood smear and by Pfs25 mRNA-NASBA, and gametocyte diversity by Pfg377 mRNA RT-PCR and RT-qPCR. RESULTS: Of the randomly selected smear-negative samples, 69.6 % (334/480) were positive by 18S-NASBA while 18S-NASBA detected 99.6 % (514/516) smear positive samples. Overall, 80.2 % of the weighted population was parasite positive by 18S-NASBA vs 30.6 % by smear diagnosis and 44.0 % of the weighted population was gametocyte positive by Pfs25-NASBA vs 2.6 % by smear diagnosis. Children 5-15 years old were more likely to be parasitaemic and gametocytaemic by NASBA than individuals >15 years old or children <5 years old while gametocyte density decreased with age. Anaemia and self-reported fever within the past 24 h were associated with increased odds of gametocytaemia. Fever was also positively associated with parasite density, but not with gametocyte density. Anti-malarial use within the past 2 weeks decreased the odds of gametocytaemia, but not the odds of parasitaemia. In contrast, recent anti-malarial use was associated with lowered parasite density, but not the gametocyte density. Use of ITNs was associated with lower odds for parasitaemia in part of the study area with a longer history of ITN interventions. In the same part of study area, the odds of having multiple gametocyte alleles were also lower in individuals using ITNs than in those not using ITNs and parasite density was positively associated with gametocyte diversity. CONCLUSION: A large proportion of submicroscopic parasites and gametocytes in western Kenya might contribute to the stagnation in malaria prevalence, suggesting that additional interventions targeting the infectious reservoir are needed. As school aged children and persons with anaemia and fever were major sources for gametocyte reservoir, these groups should be targeted for intervention and prevention to reduce malaria transmission. Anti-malarial use was associated with lower parasite density and odds of gametocytaemia, but not the gametocyte density, indicating a limitation of anti-malarial impact on the transmission reservoir. ITN use had a protective role against parasitaemia and gametocyte diversity in western Kenya.

Malaria control is hindered by the evolution and spread of resistance to antimalarials, necessitating multiple changes to drug policies over time. A comprehensive antimalarial drug resistance surveillance program is vital for detecting the potential emergence of resistance to antimalarials including current artemisinin-based combination therapies.An antimalarial drug resistance surveillance study involving 203 P. falciparum malaria-positive children was conducted in western Kenya between 2010 and 2013. Specimens from enrolled children were analyzed in vitro for sensitivity to chloroquine (CQ), amodiaquine (AQ), mefloquine (MQ), lumefantrine and artemisinin derivatives (artesunate and dihydroartemisinin), and for drug resistance allele polymorphisms in Pfcrt, Pfmdr-1 and the K13 propeller domain (K13).We observed a significant increase in the proportion of samples with the Pfcrt wild type (CVMNK) genotype, from 61.2% in 2010 to 93.0% in 2013 (p < 0.0001) and higher proportions of parasites with elevated sensitivity to CQ in vitro. The majority of isolates harbored the wild type N allele in Pfmdr-1 codon 86 (93.5 %), with only 7 (3.50%) samples with the mutant N86Y allele. Likewise, most isolates harbored the wild-type Pfmdr-1 D1246 allele (79.8%) with only 12 (6.38%) specimens with the mutant D1246Y allele and 26 (13.8%) with mixed alleles. All the samples had a single copy of the Pfmdr-1 gene (mean= 0.907+/-0.141). None of the sequenced parasites had mutations in the K13.Our results suggest that artemisinin is likely to remain highly efficacious and that CQ sensitivity appears to be on the rise in western Kenya.

BACKGROUND: Low malaria parasite densities in pregnancy are a diagnostic challenge. PCR provides high sensitivity and specificity in detecting low density of parasites, but cost and technical requirements limit its application in resources-limited settings. Pooling samples for PCR detection was explored to estimate prevalence of submicroscopic malaria infection in pregnant women at delivery. Previous work uses gold-standard based methods to calculate sensitivity and specificity of tests, creating a challenge when newer methodologies are substantially more sensitive than the gold standard. Thus prevalence was estimated using Bayesian latent class models (LCMs) in this study. METHODS: Nested PCR (nPCR) for the 18S rRNA gene subunit of Plasmodium falciparum was conducted to detect malaria infection in microscopy-negative Malawian women on IPTp. Two-step sample pooling used dried blood spot samples (DBSs) collected from placenta or periphery at delivery. Results from nPCR and histology as well as previously published data were used to construct LCMs to estimate assay sensitivity and specificity. Theoretical confidence intervals for prevalence of infection were calculated for two-step and one-step pooling strategies. RESULTS: Of 617 microscopy-negative Malawian women, 39 (6.3%) were identified as actively infected by histology while 52 (8.4%) were positive by nPCR. One hundred forty (22.7%) individuals had past infection assessed by histology. With histology as a reference, 72% of women in the active infection group, 7.1% in the past infection group and 3.2% in histology-negative group were nPCR positive. Using latent class models without a gold standard, histology had a median sensitivity of 49.7% and specificity of 97.6% for active infection while PCR had a median sensitivity of 96.0% and specificity of 99.1%. The true prevalence of active infection was estimated at 8.0% (CI: 5.8-10.5%) from PCR. PCR also had similar sensitivity for detecting either peripheral or placental malaria for submicroscopic infections. One-step pooling would give similar confidence intervals for pool sizes less than 20 while reducing the number of tests performed. CONCLUSIONS: Pooled nPCR testing was a sensitive and resource-efficient strategy and LCMs provided precise prevalence estimates of submicroscopic infections. Compared to two-step pooling, one-step pooling could provide similar prevalence estimates at population levels with many fewer tests required.

BACKGROUND: The Plasmodium falciparum dihydropteroate synthase (Pfdhps) A581 G: mutation in combination with the dhfr/dhps quintuple mutant (the "sextuple" mutant) has been associated with increased placental inflammation and decreased birthweight among women receiving intermittent preventive treatment in pregnancy with sulphadoxine-pyrimethamine (IPTp-SP). METHODS: Between 2009-2011, HIV-uninfected delivering women were enrolled in an observational study of IPTp-SP effectiveness in Malawi. Parasites were detected by polymerase chain reaction (PCR); positive samples were sequenced to genotype at dhfr and dhps loci. Presence of Pfdhps-K540 E: was used as a marker for the quintuple mutant. RESULTS: Samples from 1809 women were analysed by PCR; 220 (12%) were positive for P.falciparum. A total of 202 specimens were genotyped at codon Pfdhps-581; 17 (8.4%) harbored the sextuple mutant. The sextuple mutant was associated with higher risks of patent infection in peripheral (adjusted prevalence ratio [aPR] 2.76; 95% confidence interval 1.82-4.18) and placental blood (aPR 3.28 [1.88-5.78]), and higher parasite densities. Recent SP was not associated with increased parasite densities or placental pathology, overall and among women with dhps-A581 G: mutant parasites. CONCLUSIONS: IPTp-SP failed to inhibit parasite growth but did not exacerbate pathology among women infected with sextuple mutant parasites. New interventions to prevent malaria in pregnancy are needed urgently.