Editorial Commentary: Symptoms and Viral Shedding in Naturally Acquired Influenza Infections

The TransFLUas influenza transmission study in acute healthcare - recruitment rates and protocol adherence in healthcare workers and inpatients

Background

Detailed knowledge about viral respiratory disease transmission dynamics within healthcare institutions is essential for effective infection control policy and practice. In the quest to study viral transmission pathways, we aimed to investigate recruitment rates and adherence of healthcare workers (HCWs) and hospital inpatients with a study protocol that involves prospective surveillance based on daily mid-turbinate nasal swabs and illness diaries.

Methods

Single center prospective surveillance of patients and HCWs in three different hospital departments of a tertiary care center during an entire influenza season in Switzerland. Inpatients and acute care HCWs were asked to provide mid-turbinate nasal swabs and illness diaries on a daily basis. Study protocol adherence and recruitment rates were the primary outcomes of interest.

Results

A total 251 participants (59 (23.5%) health care workers and 192 (76.5%) inpatients) were recruited from three different hospital wards. Recruitment rates differed between HCWs (62.1% of eligible HCWs) and inpatients (32.5%; P < 0.001), but not within HCWs (P = 0.185) or inpatients (P = 0.301) of the three departments. The total number of study-days was 7874; 2321 (29.5%) for inpatients and 5553 (70.5%) for HCWs. HCWs were followed for a median of 96 days (range, 71–96 days) and inpatients for 8 days (range, 3–77 days). HCWs provided swabs on 73% (range, 0–100%) of study days, and diaries on 77% (range 0–100%). Inpatients provided swabs and diaries for 83% (range, 0–100%) of days in hospital. In HCWs, increasing age, working in internal medicine and longer duration of total study participation were positively associated with the proportion of swabs and diaries collected. Adherence to the study protocol was significantly lower in physicians as compared to nurses for both swabs (P = 0.042) and diaries (P = 0.033). In inpatients, no association between demographic factors and adherence was detected.

Conclusions Prospective surveillance of respiratory viral disease was feasible in a cohort of inpatients and HCWs over an entire influenza season, both in terms of recruitment rates and adherence to a study protocol that included daily specimen collection and illness diaries.

Trial registration

clinicaltrials.govNCT02478905. Date of registration June 23, 2015.

Prolonged shedding of type 55 human adenovirus in immunocompetent adults with adenoviral respiratory infections

Human adenovirus (HAdV) is a common pathogen causing respiratory infections with outbreaks reported in the military and community. However, little information is available on the shedding kinetics. We performed a prospective study of immunocompetent adults confirmed with HAdV respiratory infection by multiplex real-time PCR during an outbreak of HAdV-55. Consecutive respiratory specimens of sputum or nasopharyngeal swab were collected from each patient every 2 days. Viral load was measured by real-time quantitative PCR. Of 32 enrolled patients, 27 (84.4%) had pneumonia. Five patients (15.6%) received cidofovir. Viral load was highest in the earliest samples at 8.69 log₁₀ copies/mL. In a linear regression model, viral load declined consistently in a log-linear fashion at the rate of - 0.15 log₁₀ copies/mL per day (95% confidence interval (CI): - 0.18, - 0.12; R² = 0.32). However, the regression model estimated the viral shedding duration to be 55 days. The rate of decline in viral load did not differ between patients who received cidofovir and who did not. Patients with prominent respiratory symptoms or extensive involvement on chest radiograph had higher volume of viral excretion. Prolonged viral shedding was observed in otherwise healthy adults with HAdV-55 respiratory infection. This finding should be considered in the establishment of infection control and prevention strategies.

Predictors of influenza a molecular viral shedding in Hutterite communities

BACKGROUND

Patterns of influenza molecular viral shedding following influenza infection have been well established; predictors of viral shedding however remain uncertain.

OBJECTIVES

We sought to determine factors associated with peak molecular viral load, duration of shedding, and viral area under the curve (AUC) in children and adult Hutterite colony members with laboratory-confirmed influenza.

METHODS

A cohort study was conducted in Hutterite colonies in Alberta, Canada. Flocked nasal swabs were collected during three influenza seasons (2007-2008 to 2009-2010) from both symptomatic and asymptomatic individuals infected with influenza. Samples were tested by real-time reverse-transcription polymerase chain reaction for influenza A and influenza B, and the viral load was determined for influenza A-positive samples.

RESULTS

For seasonal H1N1, younger age was associated with a larger AUC, female sex was associated with decreased peak viral load and reduced viral shedding duration, while the presence of comorbidity was associated with increased peak viral load. For H3N2, younger age was associated with increased peak viral load and increased AUC. For pandemic H1N1, younger age was associated with increased peak viral load and increased viral AUC, female sex was associated with reduced peak viral load, while inapparent infection was associated with reduced peak viral load, reduced viral shedding duration, and reduced viral AUC.

CONCLUSIONS

Patterns of molecular viral shedding vary by age, sex, comorbidity, and the presence of symptoms. Predictor variables vary by influenza A subtype.