As of April 3, 2020, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) had caused 972 303 cases of coronavirus disease 2019 (COVID-19) and 50 322 deaths worldwide.¹ Early reports from China suggested that co-infection with other respiratory pathogens was rare.² If this were the case, patients positive for other pathogens might be assumed unlikely to have SARS-CoV-2. The Centers for Disease Control and Prevention endorsed testing for other respiratory pathogens, suggesting that evidence of another infection could aid the evaluation of patients with potential COVID-19 in the absence of widely available rapid testing for SARS-CoV-2.³ Here we report on co-infection rates between SARS-CoV-2 and other respiratory pathogens in Northern California.

SUMMARY: Norovirus, an RNA virus of the familyCaliciviridae, is a human enteric pathogen that causes substantial morbidity across both health care and community settings. Several factors enhance the transmissibility of norovirus, including the small inoculum required to produce infection (<100 viral particles), prolonged viral shedding, and its ability to survive in the environment. In this review, we describe the basic virology and immunology of noroviruses, the clinical disease resulting from infection and its diagnosis and management, as well as host and pathogen factors that complicate vaccine development. Additionally, we discuss overall epidemiology, infection control strategies, and global reporting efforts aimed at controlling this worldwide cause of acute gastroenteritis. Prompt implementation of infection control measures remains the mainstay of norovirus outbreak management.

Illness severity in COVID-19 correlates with specificity of serological responses, but antibody levels decrease in most patients.

A rare ability to enhance dengue virus disease: In some cases, secondary infections of dengue virus can be extremely serious and result in plasma leakage, thrombocytopenia, and hemorrhagic disease. This phenomenon has been attributed to antibody-dependent enhancement. Wang et al. show that a specific subclass of antibody, IgG1, which lacks fucosyl residues on the Fc segment of the heavy chain of the immunoglobulin, is elevated in patients with severe secondary dengue disease. These non-neutralizing antibodies bind activating Fc receptors and appear to cross-react with platelet antigens to cause platelet depletion, contributing to thrombocytopenia. Science , this issue p. 395

Zika virus (ZIKV), chikungunya virus (CHIKV), and dengue virus (DENV) cocirculate in Nicaragua. In this study, we sought to compare the quantified viremia and clinical presentation of patients infected with 1 or more of these viruses. Acute-phase serum samples from 346 patients with a suspected arboviral illness were tested using a multiplex real-time reverse-transcription polymerase chain reaction for ZIKV, CHIKV, and DENV. Viremia was quantitated for each detected virus, and clinical information from request forms submitted with each sample was recorded. A total of 263 patients tested positive for 1 or more viruses: 192 patients tested positive for a single virus (monoinfections) and 71 patients tested positive for 2 or all 3 viruses (coinfections). Quantifiable viremia was lower in ZIKV infections compared with CHIKV or DENV (mean 4.70 vs 6.42 and 5.84 log₁₀ copies/mL serum, respectively; P < .001 for both comparisons), and for each virus, mean viremia was significantly lower in coinfections than in monoinfections. Compared with patients with CHIKV or DENV, ZIKV patients were more likely to have a rash (P < .001) and less likely to be febrile (P < .05) or require hospitalization (P < .001). Among all patients, hospitalized cases had higher viremia than those who did not require hospitalization (7.1 vs 4.1 log10 copies/mL serum, respectively; P < .001). ZIKV, CHIKV, and DENV result in similar clinical presentations, and coinfections may be relatively common. Our findings illustrate the need for accurate, multiplex diagnostics for patient care and epidemiologic surveillance.