SignificanceLack of human data on influenza virus aerosol shedding fuels debate over the importance of airborne transmission. We provide overwhelming evidence that humans generate infectious aerosols and quantitative data to improve mathematical models of transmission and public health interventions. We show that sneezing is rare and not important for—and that coughing is not required for—influenza virus aerosolization. Our findings, that upper and lower airway infection are independent and that fine-particle exhaled aerosols reflect infection in the lung, opened a pathway for a deeper understanding of the human biology of influenza infection and transmission. Our observation of an association between repeated vaccination and increased viral aerosol generation demonstrated the power of our method, but needs confirmation.

A mouse-adapted enterovirus 71 (EV71) strain with increased virulence in mice, MP4, was generated after four serial passages of the parental EV71 strain 4643 in mice. Strain MP4 exhibited a larger plaque size, grew more rapidly, and was more cytotoxic in vitro than strain 4643. Although strains 4643 and MP4 both induced apoptosis of SK-N-SH human neuroblastoma cells, MP4 was more virulent than 4643 in 1-day-old mice (50% lethal doses, 10 2 and 10 4 PFU/mouse, respectively). Strain MP4 (5 ؋ 10 6 PFU/mouse), but not 4643, could orally infect 7-day-old mice, resulting in rear-limb paralysis followed by death 5 to 9 days after inoculation with the virus. Histopathologically, neuronal loss and apoptosis were evident in the spinal cords as well as the brain stems of the infected mice. The limb muscles displayed massive necrosis. There was early and transient virus replication in the intestines, whereas the spinal cord, brain, and muscle became the sites of viral replication during the late phase of the infection. Virus transmission occurred among infected and noninfected cagemates, as demonstrated by the occurrence of seroconversion and the presence of viable viruses in the stool samples of the latter. Protection against EV71 challenge was demonstrated following administration of hyperimmune serum 1 day after inoculation with the virus. Nucleotide sequence analysis of the genome of EV71 strain MP4 revealed four nucleotide changes on the 5 untranslated region, three on the VP2 region, and eight on the 2C region, resulting in one and four amino acid substitutions in the VP2 and 2C proteins, respectively.Enterovirus 71 (EV71), a neurotropic virus with undefined pathogenesis, has caused significant morbidity and mortality worldwide and especially in the Asia-Pacific region since it was first described in 1969 in the United States (1, 2). EV71 infections are generally mild, such as hand-foot-and-mouth disease (HFMD) and herpangina, but occasionally lead to severe diseases such as aseptic meningitis, poliomyelitis-like paralysis, and possibly fatal encephalitis in neonates. The outbreak of EV71 in Taiwan in 1998 killed 78 children, and since then EV71 infection has become endemic in Taiwan (8, 16). Brain stem encephalitis associated with pulmonary edema and cardiac insufficiency were the primary manifestations in patients with neurologic involvement (10, 16, 28). The predominant pathological findings were in the thalamus, pons, midbrain, medulla oblongata, and spinal cord, with intense neutrophil and mononuclear cell infiltrates. There was severe congestion with focal hemorrhage and edema in the lungs (21). Although EV71 was recovered from the mycocardium, there was only mild degeneration of the mycocardium. Neurogenic shock as a result of brain stem encephalitis has been proposed as the cause of pulmonary and cardiac complications (13,16). It has also been postulated that overwhelming virus replication combined with damage in tissues with the induction of toxic inflammatory cytokines is one possible pathogenesis (14,15,27)...

Little is known about the amount and infectiousness of influenza virus shed into exhaled breath.This contributes to uncertainty about the importance of airborne influenza transmission. We screened 355 symptomatic volunteers with acute respiratory illness and report 142 cases with confirmed influenza infection who provided 218 paired nasopharyngeal (NP) and 30-minute breath samples (coarse >5 µm and fine ≤5 µm fractions) on days 1 to 3 post symptom onset. We assessed viral RNA copy number for all samples and cultured NP swabs and fine aerosols. We SignificanceLack of human data on influenza virus aerosol shedding fuels debate over the importance of airborne transmission. We provide overwhelming evidence that humans generate infectious aerosols and quantitative data to improve mathematical models of transmission and public health interventions. We show that sneezing is rare and not important for, and that coughing is not required for influenza virus aerosolization. Our findings, that upper and lower airway infection are independent and that fine particle exhaled aerosols reflect infection in the lung, open a new pathway for understanding the human biology of influenza infection and transmission. Our observation of an association between repeated vaccination and increased viral aerosol generation demonstrated the power of our method, but needs confirmation.All rights reserved. No reuse allowed without permission.

The prevalence of three plasmid-mediated quinolone resistance determinants, QnrA, QnrB, and QnrS, among 526 nonreplicate clinical isolates of Enterobacter cloacae collected at a Taiwanese university hospital in 2004 was determined by PCR and colony hybridization, and the association of Qnr with the IMP-8 metallo-␤-lactamase was investigated. Eighty-six (16.3%) of all isolates were qnr positive, and the qnrA1-like, qnrB2-like, and qnrS1-like genes were detected alone or in combination in 3 (0.6%), 53 (10.1%), and 34 (6.5%) isolates, respectively. Among 149 putative extended-spectrum-␤-lactamase-producing isolates, 59 (39.6%) isolates, all of which were SHV-12 producers, harbored qnrA (0.7%; 1 isolate), qnrB (28.9%; 43 isolates), or qnrS (12.1%; 18 isolates). Forty-four (78.6%) of 56 IMP-8 producers carried qnrB (58.9%; 33 isolates), qnrS (25.0%; 14 isolates), or both. PCR and sequence analysis revealed that qnrA1 was located in a complex sul1-type integron that contains dhr15, aadA2, qacE⌬1, sul1, orf513, qnrA1, ampR, and qacE⌬1. Conjugation experiments revealed the coexistence of qnrB and bla IMP-8 on the transferred plasmids and the absence of ␤-lactamase content on the transferred qnrS-positive plasmids. The transferred bla IMP-8 -positive plasmids with and without qnrB had very similar restriction patterns, suggesting the horizontal mobility of qnrB. Pulsed-field gel electrophoresis showed six major patterns among the 44 qnr-positive IMP-8-producing isolates. Thus, the extremely high prevalence of qnr among the metallo-␤-lactamase-producing E. cloacae isolates in the hospital may be due mainly to the intrahospital spread of a few clones and the dissemination of plasmids containing both qnrB and bla IMP-8 .Since the first plasmid-mediated quinolone resistance determinant, Qnr (later termed QnrA), was described in a Klebsiella pneumoniae strain from the United States in 1998 (17), three major groups of Qnr determinants, QnrA, QnrB, and QnrS, have been identified in various enterobacterial species (3-14, 17, 20, 22, 33, 34). Qnr determinants may protect DNA gyrase directly from quinolone inhibition, leading to an 8-to 32-fold increase in MICs of quinolones (31). qnrA has been well known for its worldwide distribution and is located in complex sul1-type class 1 integrons (12,16,20,22,28,33). Such integrons consist of duplicate qacE⌬1 and sul1 genes, which surround a putative recombinase gene, orf513 (23). At least five qnrB and two qnrS variants have been described (1, 7-9, 11, 26), among which only qnrB2 has been found in the complex sul1-type integron (7). QnrB and QnrS have been detected in Asia, Europe, and the United States (1,4,8,9,14,24).In Taiwan, qnrS on a plasmid encoding the SHV-2 extendedspectrum ␤-lactamase (ESBL) from a K. pneumoniae strain has been described (4), and the presence of qnrA and qnrB has not been reported. The present study was conducted to determine the prevalence of the three groups of Qnr among Enterobacter cloacae isolates in a Taiwanese teaching hospital. An extraordinary high fr...