Correlation Between the Interval of Influenza Virus Infectivity and Results of Diagnostic Assays in a Ferret Model

Care, management, and use of ferrets in biomedical research

The ferret (Mustela putorius furo) is a small domesticated species of the family Mustelidae within the order Carnivora. The present article reviews and discusses the current state of knowledge about housing, care, breeding, and biomedical uses of ferrets. The management and breeding procedures of ferrets resemble those used for other carnivores. Understanding its behavior helps in the use of environmental enrichment and social housing, which promote behaviors typical of the species. Ferrets have been used in research since the beginning of the twentieth century. It is a suitable non-rodent model in biomedical research because of its hardy nature, social behavior, diet and other habits, small size, and thus the requirement of a relatively low amount of test compounds and early sexual maturity compared with dogs and non-human primates. Ferrets and humans have numerous similar anatomical, metabolic, and physiological characteristics, including the endocrine, respiratory, auditory, gastrointestinal, and immunological systems. It is one of the emerging animal models used in studies such as influenza and other infectious respiratory diseases, cystic fibrosis, lung cancer, cardiac research, gastrointestinal disorders, neuroscience, and toxicological studies. Ferrets are vulnerable to many human pathogenic organisms, like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), because air transmission of this virus between them has been observed in the laboratory. Ferrets draw the attention of the medical community compared to rodents because they occupy a distinct niche in biomedical studies, although they possess a small representation in laboratory research.

Viral Burden and Clearance in Asymptomatic COVID-19 Patients

Background

Containing coronavirus disease 2019 (COVID-19) has been difficult, due to both the large number of asymptomatic infected individuals and the long duration of infection. Managing these challenges requires understanding of the differences between asymptomatic vs symptomatic patients and those with a longer duration of infectivity.

Methods

Individuals from Los Angeles were tested for COVID-19, and a group positive for COVID-19 chose to have follow-up testing. Associations between symptoms and demographic factors, viral burden measured by cycle threshold (CT) value, and duration of polymerase chain reaction (PCR) positivity were analyzed.

Results

Eighteen point eight percent of patients were positive for COVID-19. Asymptomatic COVID-19-positive patients were significantly younger than symptomatic patients (2.6 years; P < .001). There were no differences in average CT between asymptomatic and symptomatic patients. The estimated median duration of COVID-19 PCR positivity was 23 days. Being asymptomatic throughout the course of infection was the only factor associated with a shorter course of COVID-19 PCR positivity (21 vs 28 days; P = .002).

Conclusions

We found important differences and similarities between asymptomatic and symptomatic COVID-19-positive patients, the most meaningful being a similar level of virus as measured by PCR, but a shorter duration of PCR positivity for asymptomatic patients. These findings suggest that asymptomatic patients may have more efficient clearance of virus, which may be relevant for management and screening.

Clinical validation of automated and rapid mariPOC SARS-CoV-2 antigen test

COVID-19 diagnostics was quickly ramped up worldwide early 2020 based on the detection of viral RNA. However, based on the scientific knowledge for pre-existing coronaviruses, it was expected that the SARS-CoV-2 RNA will be detected from symptomatic and at significant rates also from asymptomatic individuals due to persistence of non-infectious RNA. To increase the efficacy of diagnostics, surveillance, screening and pandemic control, rapid methods, such as antigen tests, are needed for decentralized testing and to assess infectiousness. A novel automated mariPOC SARS-CoV-2 test was developed for the detection of conserved structural viral nucleocapsid proteins. The test utilizes sophisticated optical laser technology for two-photon excitation and individual detection of immunoassay solid-phase particles. We validated the new method against qRT-PCR. Sensitivity of the test was 100.0% (13/13) directly from nasopharyngeal swab specimens and 84.4% (38/45) from swab specimens in undefined transport mediums. Specificity of the test was 100.0% (201/201). The test's limit of detection was 2.7 TCID₅₀/test. It showed no cross-reactions. Our study shows that the new test can detect infectious individuals already in 20 min with clinical sensitivity close to qRT-PCR. The mariPOC is a versatile platform for syndromic testing and for high capacity infection control screening of infectious individuals.

Sustainable chemical preventive models in COVID-19: Understanding, innovation, adaptations, and impact

COVID-19 is considered as a major public health problem caused by the SARS CoV-2. This Viral infection is known to induce worldwide pandemic in short period of time. Emerging evidence suggested that the transmission control and drug therapy may influence the preventive measures extensively as the host surrounding environment and pathogenic mechanism may contribute to the pandemic condition earlier in COVID-19 disease. Although, several animals identified as reservoir to date, however human-to-human transmission is well documented. Human beings are sustaining the virus in the communities and act as an amplifier of the virus. Human activities i.e., living with the patient, touching patient waste etc. in the surrounding of active patients or asymptomatic persons cause significant risk factors for transmission. On the other hand, drug target and mechanism to destroy the virus or virus inhibition depends on diversified approaches of drugs and different target for virus life cycle. This article describes the sustainable chemical preventive models understanding, requirements, technology adaptation and the implementation strategies in these pandemic-like situations. As the outbreak progresses, healthcare models focused on transmission control through disinfections and sanitization based on risk calculations. Identification of the most suitable target of drugs and regional control model of transmission are of high priority. In the early stages of an outbreak, availability of epidemiological information is important to encourage preventive measures efforts by public health authorities and provide robust evidence to guide interventions. Here, we have discussed the level of adaptations in technology that research professionals display toward their public health preventive models. We should compile a representative data set of adaptations that humans can consider for transmission control and adopt for viruses and their hosts. Overall, there are many aspects of the chemical science and technology in virus preventive measures. Herein, the most recent advances in this context are discussed, and the possible reasons behind the sustainable preventive model are presented. This kind of sustainable preventive model having adaptation and implementation with green chemistry system will reduce the shedding of the virus into the community by eco-friendly methods, and thus the risk of transmission and infection progression can be mitigated.

A(H1N1)pdm09 influenza viruses replicating in ferret upper or lower respiratory tract differed in onward transmission potential by air

BACKGROUND

A(H1N1)pdm09 influenza viruses replicate efficiently in respiratory epithelia and are transmitted via respiratory droplets and aerosols expelled by infected hosts. The relative onward transmission potential of influenza viruses replicating in the upper and lower respiratory epithelial cells has not been fully defined.

METHODS

Wild-type and barcoded A(H1N1)pdm09 viruses that differed by 2 synonymous mutations per gene segment were inoculated into ferrets via intra-nasal and intra-tracheal routes. Naïve recipients were exposed to the exhaled breath of inoculated donors for 8 hours on day 2 post-inoculation. Onward transmission potential of wild-type and barcoded genotypes were monitored by next generation sequencing.

RESULTS

Transmissible airborne particles were respired from the upper but not the lower respiratory epithelial cells of donor ferrets. There was limited mixing of viral populations replicating in the upper and lower respiratory tissues.

CONCLUSIONS

The ferret upper respiratory epithelium was mapped as the anatomic site that generated influenza virus-laden particles mediating onward transmission by air. Our results suggest that vaccines and antivirals should aim to reduce viral loads in the upper respiratory tract for prevention of influenza transmission.

Oseltamivir treatment of influenza A and B infections in infants

Background

Oseltamivir treatment is currently the only way of managing influenza in young infants for whom influenza vaccines are not licensed, but little data exist on the effectiveness of the treatment in this age group.

Methods

In a prospective study, we enrolled 431 newborn infants and followed them up for 10 months during their first respiratory season (September 2017‐June 2018). During each respiratory illness, we examined the infants and obtained nasopharyngeal specimens for determination of the viral etiology. Infants with influenza were re‐examined at short intervals, and additional nasopharyngeal specimens were obtained at each visit for measuring the viral load. All infants with symptoms <48 hours received oseltamivir treatment. The parents filled out daily symptom diaries.

Results

Among 23 infants with influenza A, the mean total duration of illness in oseltamivir recipients was 82.1 hours, compared with 253.5 hours in infants without treatment (P = .0003). For infants with influenza B, the corresponding durations were 110.0 and 173.9 hours, respectively (P = .03). In infants with influenza A, total symptom scores were significantly lower in oseltamivir‐treated infants at all time points between days 3 and 11 after the onset of therapy. In most children with either influenza A or B, viral antigen concentrations declined rapidly within 1‐2 days after the initiation of oseltamivir treatment.

Conclusions

Oseltamivir treatment of infants with influenza rapidly decreased the viral load in nasopharyngeal secretions and shortened the duration and severity of symptoms. The clinical effectiveness of oseltamivir appeared to be greater against influenza A than against influenza B infections.

Potential sources, modes of transmission and effectiveness of prevention measures against SARS-CoV-2

During the current SARS-CoV-2 pandemic new studies are emerging daily providing novel information about sources, transmission risks and possible prevention measures. In this review, we aimed to comprehensively summarize the current evidence on possible sources for SARS-CoV-2, including evaluation of transmission risks and effectiveness of applied prevention measures. Next to symptomatic patients, asymptomatic or pre-symptomatic carriers are a possible source with respiratory secretions as the most likely cause for viral transmission. Air and inanimate surfaces may be sources; however, viral RNA has been inconsistently detected. Similarly, even though SARS-CoV-2 RNA has been detected on or in personal protective equipment (PPE), blood, urine, eyes, the gastrointestinal tract and pets, these sources are currently thought to play a negligible role for transmission. Finally, various prevention measures such as handwashing, hand disinfection, face masks, gloves, surface disinfection or physical distancing for the healthcare setting and in public are analysed for their expected protective effect.

Respiratory pathogen diversity and co-infections in rural Zambia

Objectives:

The role of respiratory co-infections in modulating disease severity remains understudied in southern Africa, particularly in rural areas. This study was performed to characterize the spectrum of respiratory pathogens in rural southern Zambia and the prognostic impact of co-infections.

Methods:

Respiratory specimens collected from inpatient and outpatient participants in a viral surveillance program in 2018–2019 were tested for selected viruses and a typical bacteria using the Xpert Xpress Flu/RSV assay and FilmArray Respiratory Panel EZ. Participants were followed for 3–5 weeks to assess their clinical course. Multivariable regression was used to examine the role of co-infections in influencing disease severity.

Results:

A respiratory pathogen was detected in 63.2% of samples from 671 participants who presented with influenza-like illness. Common pathogens identified included influenza virus (18.2% of samples), respiratory syncytial virus (RSV) (11.8%), rhinovirus (26.4%), and coronavirus (6.0%). Overall, 6.4% of participants were co-infected with multiple respiratory pathogens. Compared to mono-infections, co-infections were found not to be associated with severe clinical illness either overall (relative risk (RR) 0.72, 95% confidence interval (CI) 0.39–1.32) or specifically with influenza virus (RR 0.80, 95% CI 0.14–4.46) or RSV infections (RR 0.44, 95% CI 0.17–1.11).

Conclusions:

Respiratory infections in rural southern Zambia were associated with a wide range of viruses. Respiratory co-infections in this population were not associated with clinical severity.

Persistence of SARS-CoV-2 nasopharyngeal swab PCR positivity in COVID-19 convalescent plasma donors

BACKGROUND

Nucleic acid persists after symptom resolution and infectivity for many viral infections via delayed clearance of nucleic acid fragments, non-infectious particles, or transmissible virus. For Coronavirus Disease 2019 (COVID-19), the relationship between nasopharyngeal (NP) swab positivity, the development of antibodies against COVID-19, and clinical history are unclear.

STUDY DESIGN AND METHODS

Individuals who recovered from COVID-19 and volunteered to donate convalescent plasma (CP) were screened by NP swab PCR, responded to a questionnaire, and were tested for anti-COVID-19 antibodies.

RESULTS

A proportion of 11.8% of individuals tested positive for SARS-CoV-2 by NP swab PCR greater than 14 days after the resolution of symptoms of active disease, including one donor who had asymptomatic disease and tested positive by NP swab 41 days after her initial diagnosis. Clinical history did not show a significant correlation with persistence of NP swab positivity. Also, NP swab positivity >14 days from symptom resolution did not correlate with anti-COVID-19 serology results. IgG anti-SARS-CoV-2 spike antibody strength correlated with hospitalization for COVID-19 using two different assays. Total anti-SARS-CoV-2 nucleocapsid antibody strength correlated with time from symptom resolution to sample collection and symptom duration.

CONCLUSIONS

SARS-CoV-2 nucleic acid is detectable long after the resolution of symptoms in a significant percentage of previously diagnosed individuals, which is important to consider when interpreting PCR swab results. Persistence of PCR positivity does not correlate with antibody strength or symptoms of COVID-19. If anti-spike antibody is used to assess CP potency, individuals who suffered severe COVID-19 disease symptoms may represent better donors.

A Guide for the Use of the Ferret Model for Influenza Virus Infection

As influenza viruses continue to jump species barriers to cause human infection, assessments of disease severity and viral replication kinetics in vivo provide crucial information for public health professionals. The ferret model is a valuable resource for evaluating influenza virus pathogenicity; thus, understanding the most effective techniques for sample collection and usage, as well as the full spectrum of attainable data after experimental inoculation in this species, is paramount. This is especially true for scheduled necropsy of virus-infected ferrets, a standard component in evaluation of influenza virus pathogenicity, as necropsy findings can provide important information regarding disease severity and pathogenicity that is not otherwise available from the live animal. In this review, we describe the range of influenza viruses assessed in ferrets, the measures of experimental disease severity in this model, and optimal sample collection during necropsy of virus-infected ferrets. Collectively, this information is critical for assessing systemic involvement after influenza virus infection in mammals.

Implementation of influenza point-of-care testing and patient cohorting during a high-incidence season: a retrospective analysis of impact on infection prevention and control and clinical outcomes

BACKGROUND

During high-incidence influenza seasons, a robust infection prevention and control policy is imperative to reduce nosocomial transmission of influenza.

AIM

To assess the impact of influenza point-of-care testing (POCT) in an emergency department (ED) and patient cohorting on an influenza ward on infection prevention and control and clinical outcomes.

METHODS

Influenza POCT was operational in the study ED from 21^st January 2018 and patient cohorting was operational on an influenza ward from 25^th January 2018. A retrospective 'before-after' analysis was performed with pre-intervention defined as 1^st November 2017 to 20^th January 2018 and post-intervention defined as 21^st January 2018 to 30^th April 2018. The primary outcome was the rate of hospital-acquired influenza. Secondary outcomes included antiviral prescription and length of stay. The length of time that inpatients remained influenza-positive was estimated by polymerase chain reaction (PCR).

FINDINGS

There were 654 inpatients with confirmed influenza during the 2017/18 influenza season: 223 pre- and 431 post-intervention. Post-intervention, there were fewer cases of hospital-acquired influenza per day (0.66 vs 0.95, P < 0.0001), median length of stay was shorter (5.5 vs 7.5 days, P = 0.005) and antiviral prescription was more frequent (80% vs 64.1%, P < 0.0001). Cohorting released 779 single rooms for use elsewhere in the trust. The fixed probability of being PCR-negative by the next day (P) was 0.14 [95% confidence interval (CI) 0.12-0.16] for immunocompetent patients. This implies that half of immunocompetent patients are PCR-negative by five days post-diagnosis (95% CI 5-6).

CONCLUSION

Influenza POCT in an ED and patient cohorting on an influenza ward were associated with reduced nosocomial transmission of influenza and improved patient flow. A policy of retesting immunocompetent patients five days post-diagnosis could allow half of these patients to come out of respiratory isolation earlier.

Rapid detection and monitoring of human coronavirus infections

Human coronaviruses (CoVs) are increasingly recognized as important respiratory pathogens associated with a broad range of clinical diseases. We sought to increase the insight into clinically relevant CoV infections by monitoring antigen concentrations in six confirmed CoV-positive patients using a newly developed assay for rapid detection of CoV OC43 infections. Antigen positivity lasted 3 to 6 days in secondary infections and 13 days in primary infection. CoV infections are clinically diverse, are common, and cannot be diagnosed from clinical symptoms alone.

The PA Endonuclease Inhibitor RO-7 Protects Mice from Lethal Challenge with Influenza A or B Viruses

Current influenza treatment relies on a single class of antiviral drugs, the neuraminidase inhibitors (NAIs), raising concern over the potential emergence of resistant variants and necessitating the development of novel drugs. In recent years, investigational inhibitors targeting the endonuclease activity of the influenza acidic polymerase (PA) protein have yielded encouraging results, although there are only limited data on their in vivo efficacy. Here, we examined the antiviral potential of the PA endonuclease inhibitor RO-7 in prophylactic and therapeutic regimens in BALB/c mice inoculated with influenza A/California/04/2009 (H1N1)pdm09 or B/Brisbane/60/2008 viruses, which represent currently circulating antigenic variants. RO-7 was administered to mice intraperitoneally twice daily at dosages of 6, 15, or 30 mg/kg/day for 5 days, starting 4 h before or 24 or 48 h after virus inoculation, and showed no adverse effects. Prophylactic administration completely protected mice from lethal infection by influenza A or B virus. The level of therapeutic protection conferred depended upon the time of treatment initiation and RO-7 dosage, resulting in 60 to 100% and 80 to 100% survival with influenza A and B viruses, respectively. RO-7 treatment significantly decreased virus titers in the lung and lessened the extent and severity of lung damage. No PA endonuclease-inhibitor resistance was observed in viruses isolated from lungs of RO-7-treated mice, and the viruses remained susceptible to the drug at nanomolar concentrations in phenotypic assays. These in vivo efficacy results further highlight the potential of RO-7 for development as antiviral therapy for influenza A and B virus infections.

Simulated Respiratory Secretion for Use in the Development of Influenza Diagnostic Assays

Many assays have been developed for the detection of influenza virus which is an important respiratory pathogen. Development of these assays commonly involves the use of human clinical samples for validation of their performance. However, clinical samples can be difficult to obtain, deteriorate over time, and be inconsistent in composition. The goal of this study was to develop a simulated respiratory secretion (SRS) that could act as a surrogate for clinical samples. To this end, we determined the effects major respiratory secretion components (Na⁺, K⁺, Ca²⁺, cells, albumin IgG, IgM, and mucin) have on the performance of influenza assays including both nucleic acid amplification and rapid antigen assays. Minimal effects on the molecular assays were observed for all of the components tested, except for serum derived human IgG, which suppressed the signal of the rapid antigen assays. Using dot blots we were able to show anti-influenza nucleoprotein IgG antibodies are common in human respiratory samples. We composed a SRS that contained mid-point levels of human respiratory sample components and studied its effect compared to phosphate buffered saline and virus negative clinical sample matrix on the Veritor, Sofia, CDC RT-PCR, Simplexa, cobas Liat, and Alere i influenza assays. Our results demonstrated that a SRS can interact with a variety of test methods in a similar manner to clinical samples with a similar impact on test performance.

Influenza Virus Detection Following Administration of Live-Attenuated Intranasal Influenza Vaccine in Children With Cystic Fibrosis and Their Healthy Siblings

Background.  We aimed to explore the detection profile of influenza viruses following live-attenuated intranasal influenza vaccination (LAIV) in children aged 2-19 years with and without cystic fibrosis (CF). Methods.  Before the 2013-2014 influenza season, flocked nasal swabs were obtained before vaccination and 4 times in the week of follow-up from 76 participants (n_CF: 57; n_healthy: 19). Influenza was detected by reverse transcription polymerase chain reaction (RT-PCR) assays. A Bayesian hierarchical logistic regression model was used to estimate the effect of CF status and age on influenza detection. Results.  Overall, 69% of the study cohort shed influenza RNA during follow-up. The mean duration of RT-PCR detection was 2.09 days (95% credible interval [CrI]: 1.73-2.48). The odds of influenza RNA detection on day 1 following vaccination decreased with age in years (odds ratio [OR]: 0.82 per year; 95% CrI: 0.70-0.95), and subjects with CF had higher odds of influenza RNA detection on day 1 of follow-up (OR: 5.09; 95% CrI: 1.02-29.9). Conclusion.  Despite the small sample size, our results indicate that LAIV vaccine strains are detectable during the week after LAIV, mainly in younger individuals and vaccinees with CF. It remains unclear whether recommendations for avoiding contact with severely immunocompromised patients should differ for these groups.

Complexities in Ferret Influenza Virus Pathogenesis and Transmission Models

Ferrets are widely employed to study the pathogenicity, transmissibility, and tropism of influenza viruses. However, inherent variations in inoculation methods, sampling schemes, and experimental designs are often overlooked when contextualizing or aggregating data between laboratories, leading to potential confusion or misinterpretation of results. Here, we provide a comprehensive overview of parameters to consider when planning an experiment using ferrets, collecting data from the experiment, and placing results in context with previously performed studies. This review offers information that is of particular importance for researchers in the field who rely on ferret data but do not perform the experiments themselves. Furthermore, this review highlights the breadth of experimental designs and techniques currently available to study influenza viruses in this model, underscoring the wide heterogeneity of protocols currently used for ferret studies while demonstrating the wealth of information which can benefit risk assessments of emerging influenza viruses.

Evaluation of a smartphone-based rapid fluorescent diagnostic system for H9N2 virus in specific-pathogen-free chickens

Repeated interspecies transmission of H9N2 virus from poultry to humans and human infections transmitted via aerosols highlight the need for a highly sensitive, rapid diagnostic system for the detection of this virus. However, no such test exhibiting high performance has been developed. In this study, the performance of a smartphone-based rapid fluorescent diagnostic system (SRFDS) was optimized for the diagnosis of an H9N2-virus-infected animal. To suppress the nonspecific reactivity of the bioconjugate in oropharyngeal (OP) and cloacal (CL) samples derived from chickens, different blocking reagents were tested, and a mixture of casein and sucrose was found to be optimal. To assess the performance of SRFDS, OP and CL samples were obtained from specific-pathogen-free chickens and used for comparison of this method with real-time reverse transcription PCR (rRT-PCR) at time points of three, five, and seven days postinfection (dpi). The limit of detection of SRFDS was found to be 7.5 PFU/mL, which was 138-fold higher than that of a conventional colloidal-gold-based avian influenza rapid diagnostic test. In the animal study, the presence of viral antigen was monitored with SRFDS, and the relative sensitivity (relative to rRT-PCR results) was 94.44 % (17/18) and 95.23 % (20/21) in OP and CL specimens, respectively. The specificity of SRFDS was 100 %. These results imply that the diagnostic performance of SRFDS might be comparable to that of rRT-PCR for diagnosis of H9N2 in chickens and that this test can be used as a highly sensitive rapid diagnostic method in field studies on broiler poultry and wild birds.