Respiratory Influenza viral load as a marker of poor prognosis in patients with severe symptoms

Association of viral loads of influenza A (H3N2) with age and care setting on presentation-a prospective study during the 2022-2023 influenza season in Spain

OBJECTIVES

The aim of this study was to analyze the viral load (VL) using cycle threshold (Ct) in patients infected with influenza A (H3N2).

METHODS

This prospective study was conducted during the 2022-2023 influenza season in sentinel, non-sentinel, and hospitalized patients of Castilla y León (Spain). Respiratory samples were obtained from nasopharyngeal swabs and analyzed by quantitative reverse transcription-polymerase chain reaction specific for influenza A (H3N2) to obtain the Ct value.

RESULTS

A total of 1047 individuals were enrolled (174 [16.6%] sentinel, 200 [19.1%] non-sentinel, 673 [64.3%] hospitalized). The mean Ct value was lower in infants, young children, and in the elderly, with a sharp increase in the last from 65 years until 90 years. In addition, the lower Ct values were observed in non-sentinel patients and then in hospitalized patients, probably because non-sentinel are outpatients in the acute phase of the influenza infection.

CONCLUSIONS

A higher VL (lower Ct value) is related to the extreme ages of life: children and the elderly. Furthermore, a higher VL is related with the care setting, being probably higher in outpatients because they are in the acute phase of the disease and slightly lower in hospitalized patients because they are attended during the post-acute phase.

Viral Pneumonia: From Influenza to COVID-19

Respiratory viruses are increasingly recognized as a cause of community-acquired pneumonia (CAP). The implementation of new diagnostic technologies has facilitated their identification, especially in vulnerable population such as immunocompromised and elderly patients and those with severe cases of pneumonia. In terms of severity and outcomes, viral pneumonia caused by influenza viruses appears similar to that caused by non-influenza viruses. Although several respiratory viruses may cause CAP, antiviral therapy is available only in cases of CAP caused by influenza virus or respiratory syncytial virus. Currently, evidence-based supportive care is key to managing severe viral pneumonia. We discuss the evidence surrounding epidemiology, diagnosis, management, treatment, and prevention of viral pneumonia.

Aerosolized nicotine from e-cigarettes alters gene expression, increases lung protein permeability, and impairs viral clearance in murine influenza infection

E-cigarette use has rapidly increased as an alternative means of nicotine delivery by heated aerosolization. Recent studies demonstrate nicotine-containing e-cigarette aerosols can have immunosuppressive and pro-inflammatory effects, but it remains unclear how e-cigarettes and the constituents of e-liquids may impact acute lung injury and the development of acute respiratory distress syndrome caused by viral pneumonia. Therefore, in these studies, mice were exposed one hour per day over nine consecutive days to aerosol generated by the clinically-relevant tank-style Aspire Nautilus aerosolizing e-liquid containing a mixture of vegetable glycerin and propylene glycol (VG/PG) with or without nicotine. Exposure to the nicotine-containing aerosol resulted in clinically-relevant levels of plasma cotinine, a nicotine-derived metabolite, and an increase in the pro-inflammatory cytokines IL-17A, CXCL1, and MCP-1 in the distal airspaces. Following the e-cigarette exposure, mice were intranasally inoculated with influenza A virus (H1N1 PR8 strain). Exposure to aerosols generated from VG/PG with and without nicotine caused greater influenza-induced production in the distal airspaces of the pro-inflammatory cytokines IFN-γ, TNFα, IL-1β, IL-6, IL-17A, and MCP-1 at 7 days post inoculation (dpi). Compared to the aerosolized carrier VG/PG, in mice exposed to aerosolized nicotine there was a significantly lower amount of Mucin 5 subtype AC (MUC5AC) in the distal airspaces and significantly higher lung permeability to protein and viral load in lungs at 7 dpi with influenza. Additionally, nicotine caused relative downregulation of genes associated with ciliary function and fluid clearance and an increased expression of pro-inflammatory pathways at 7 dpi. These results show that (1) the e-liquid carrier VG/PG increases the pro-inflammatory immune responses to viral pneumonia and that (2) nicotine in an e-cigarette aerosol alters the transcriptomic response to pathogens, blunts host defense mechanisms, increases lung barrier permeability, and reduces viral clearance during influenza infection. In conclusion, acute exposure to aerosolized nicotine can impair clearance of viral infection and exacerbate lung injury, findings that have implications for the regulation of e-cigarette products.

Using Discarded Facial Tissues to Monitor and Diagnose Viral Respiratory Infections

Molecular biology amplification enables sensitive detection of most respiratory viruses through nasopharyngeal swabbing. We developed an innovative approach to detect viral genomes on used facial tissues. In 2 communities of children, used tissues were collected once weekly for 1 year. Pooled analysis of tissues enabled detection of successive virus circulation in 4 age groups over time and forecasted by several weeks the circulation of influenza in the general population. At the individual level, in a proof-of-concept study of 30 volunteers with influenza-like signs/symptoms, we identified common respiratory viruses. The signals for SARS-CoV-2 obtained in parallel from 15 facial tissues and swab samples were similar and often higher for the tissues (11/15). Individual analysis of tissues offers a noninvasive, sensitive, and affordable alternative to self-sampling without a medical care requirement. Pooled analyses may be used to detect virus spread in specific communities, predict seasonal epidemics, and alert the population to viral infections.

Moderate to severe ARDS: COVID-19 patients compared to influenza patients for ventilator parameters and mortality

Background

This study aimed to compare ventilatory parameters recorded the first days of ARDS, and mortality at day 60 between COVID-19 and influenza ARDS patients with PaO2/FiO2≤150 mmHg.

Methods

We compared 244 COVID-19 ARDS patients with 106 influenza ARDS patients. Driving pressure (DP), respiratory system compliance (CRs), ventilator ratio (VR), corrected minute ventilation (VEcorr), and surrogate of mechanical power [index=(4×DP)+respiratory rate] were calculated from day1 to day 5 of ARDS. A propensity score analysis and a principal component analysis (PCA) were performed.

Results

On day 1 of ARDS, COVID-19 patients had significantly higher PaO2/FiO2ratio (median [IQR], 97 mmHg [79–129]versus83 [62.2–114]), p=0.001), and lower DP (13 cmH20 [11–16.0]versus14 [12.0–16.7], p=0.01), VR (2.08 [1.73–2.49versus2.52 [1.97–3.03], p<0.001), VEcorr (12.7 L·mn−1[10.2–14.9]versus14.9 [11.6–18.6], p<0.001), index (80 [70–89]versus84 [75–94], p=0.004). PCA demonstrated an important overlap of ventilatory parameters recorded on day 1 between the two groups. From day 1 to day 5 repeated values of PaO2/FiO2ratio, PaCO2, VR and VEcorr differed significantly between influenza and COVID-19 patients in the unmatched and matched populations. Mortality at day 60 did not differ significantly after matching (29%versus21.7%, p=0.43).

Conclusions

Ventilation was more impaired in influenza than in COVID-19 ARDS patients the first day of ARDS with important overlap of values. However, mortality at day 60 did not differ significantly in the matched population.

Severe Infections Due to Respiratory Viruses

Severe viral infections may result in severe illnesses capable of causing acute respiratory failure that could progress rapidly to acute respiratory distress syndrome (ARDS), related to worse outcomes, especially in individuals with a higher risk of infection, including the elderly and those with comorbidities such as asthma, diabetes mellitus and chronic respiratory or cardiovascular disease. In addition, in cases of severe viral pneumonia, co-infection with bacteria such as Streptococcus pneumoniae and Staphylococcus aureus is related to worse outcomes. Respiratory viruses like influenza, rhinovirus, parainfluenza, adenovirus, metapneumovirus, respiratory syncytial virus, and coronavirus have increasingly been detected. This trend has become more prevalent, especially in critically ill patients, due to the availability and implementation of molecular assays in clinical practice. Respiratory viruses have been diagnosed as a frequent cause of severe pneumonia, including cases of community-acquired pneumonia, hospital-acquired pneumonia, and ventilator-associated pneumonia. In this review, we will discuss the epidemiology, diagnosis, clinical characteristics, management, and prognosis of patients with severe infections due to respiratory viruses, with a focus on influenza viruses, non-influenza viruses, and coronaviruses.

Importance of Adequate qPCR Controls in Infection Control

Respiratory screening assays lacking Sample Adequacy Controls (SAC) may result in inadequate sample quality and thus false negative results. The non-adequate samples might represent a significant proportion of the total performed tests, thus resulting in sub-optimal infection control measures with implications that may be critical during pandemic times. The quantitative sample adequacy threshold can be established empirically, measuring the change in the frequency of positive results, as a function of the numerical value of “sample adequacy”. Establishing a quantitative threshold for SAC requires a big number/volume of tests to be analyzed in order to have a statistically valid result. Herein, we are offering for the first time clear clinical evidence that a subset of results, which did not pass minimal sample adequacy criteria, have a significantly lower frequency of positivity compared with the “adequate” samples. Flagging these results and/or re-sampling them is a mitigation strategy, which can dramatically improve infection control measures.

Acute Respiratory Distress Syndrome: Focus on Viral Origin and Role of Pulmonary Lymphatics

Acute respiratory distress syndrome (ARDS) is a serious affection of the lung caused by a variety of pathologies. Great interest is currently focused on ARDS induced by viruses (pandemic influenza and corona viruses). The review describes pulmonary changes in ARDS and specific effects of the pandemic viruses in ARDS, and summarizes treatment options. Because the known pathogenic mechanisms cannot explain all aspects of the syndrome, the contribution of pulmonary lymphatics to the pathology is discussed. Organization and function of lymphatics in a healthy lung and in resorption of pulmonary edema are described. A future clinical trial may provide more insight into the role of hyaluronan in ARDS but the development of promising pharmacological treatments is unlikely because drugs play no important role in lymphedema therapy.

Frequent lower respiratory tract disease in hematological patients with parainfluenza virus type 3 infection

Human parainfluenza virus type 3 (HPIV-3) may cause lower respiratory tract infection disease (LRTI-D) after hematopoietic stem cell transplantation (HSCT). Most previous have studies focused on recipients of HSCT whereas data on characteristics and outcomes in patients with hematological malignancies (HMs) compared to non-hematological patients are limited. The prognostic value of viral load in respiratory specimens remains elusive. In a 2-year retrospective study, we determined the frequencies of LRTI-D in HM, HSCT, and in non-hematological patients, and HPIV-3 levels in respiratory tract secretions. Among 98 patients with HPIV-3 infection, including 31 HSCT and 40 HM, 36 had a diagnosis of LRTI-D. LRTI-D was significantly more frequent in patients with HM or HSCT (n = 32, 45.1%) than in non-hematological patients (n = 4, 14.8%) (p = 0.006). The median HPIV-3 loads were high in upper respiratory tract secretions regardless of the presence or absence of LRTI-D (8.3 log₁₀ vs. 7.6 log₁₀ TCID₅₀ /10⁶ cells). HPIV-3 loads in respiratory tract samples in HM were not significantly higher than those found in HSCT but significantly higher than in non-hematological patients (p = 0.007). In conclusion, LRTI-D was frequent in HM patients who were diagnosed with HPIV-3 infection.

Coinfection of Parvovirus B19 with Influenza A/H1N1 Causes Fulminant Myocarditis and Pneumonia. An Autopsy Case Report

Parvovirus-B19 (PVB19) is a frequent causative agent of myocarditis. For unclear reasons, viral reactivation can cause acute myocarditis, a leading cause of sudden death in the young. Influenza A/H1N1(2009) virus (IAV/H1N1) is known for causing flu/pneumonia, but the heart is rarely involved. Co-infections of cardiotropic viruses are rarely reported and the mechanisms of viral interactions remain unknown. A 5-year old girl had a flu-like syndrome, when she suddenly presented with a respiratory distress and cardiac arrest. At autopsy, the lungs were found haemorrhagic. Lungs’ histology showed severe bronchiolitis, diffuse haemorrhagic necrosis, and mononuclear inflammation. In the heart, a moderate inflammation was found with no necrosis. IAV/H1N1 was detected in nasal and tracheal swabs, lungs, and the heart. The viral load was high in the lungs, but low in the heart. PVB19 was detected in the heart with a high viral load. Viral co-infection increases the risk of severe outcome but the mechanisms of interaction between viruses are poorly understood. In our case, viral loads suggested a reactivated PVB19-induced acute myocarditis during an IAV/H1N1 pneumonia. Viral interactions may involve an IAV/H1N1-induced cytokine storm, with a fulminant fatal outcome. Clinically, our case shows the importance of investigating inflammatory pathways as therapeutic targets.