The epidemiological and public health research response to 2009 pandemic influenza A(H1N1): experiences from Hong Kong

Psychological impact of COVID-19 after hospital discharge: A follow-up study on Italian recovered patients

BACKGROUND

Since COVID-19 outbreak, clinical experience on its management during the acute phase has rapidly grown, including potential effects on the psychopathological dimension. However, still few data are available regarding the impact on survivors' mental health over the long-term.

METHODS

A sample of 1457 COVID-19 patients underwent a multidisciplinary follow-up protocol, approximately 3 months after hospital discharge, including a psychological evaluation. The primary outcomes were anxiety, depression, resilience, post-traumatic symptoms, and health-related quality of life. Furthermore, we examined the potential role of hospitalization and delay in the follow-up assessment on the increased burden of illness.

RESULTS

Although a general high level of resilience emerged, suggesting most patients relied on their individual and interpersonal resources to face difficulties related to the pandemic, almost one third of the sample reported signs of psychological distress over time, especially post-traumatic symptoms, with anxiety being more represented than depression. Furthermore, hospitalization - regardless of the setting of care - and promptness in follow-up evaluation were found to play a protective role on patients' recovery and mental wellbeing.

LIMITATIONS

Selection bias of patients exclusively admitted to the hospital; absence of a control group; psychological assessment relying on self-reported instruments.

CONCLUSIONS

The current crisis demands resilience and adjustment resources, either in the acute and post-acute phase. Thus, the clinical effort should aim at relieving the traumatic impact of such condition through timely interventions. Further investigation may address potential predictors of developing a traumatic stress response, in order to identify and promptly treat at-risk subpopulations.

Interpreting Seroepidemiologic Studies of Influenza in a Context of Nonbracketing Sera

BACKGROUND

In influenza epidemiology, analysis of paired sera collected from people before and after influenza seasons has been used for decades to study the cumulative incidence of influenza virus infections in populations. However, interpretation becomes challenging when sera are collected after the start or before the end of an epidemic, and do not neatly bracket the epidemic.

METHODS

Serum samples were collected longitudinally in a community-based study. Most participants provided their first serum after the start of circulation of influenza A(H1N1)pdm09 virus in 2009. We developed a Bayesian hierarchical model to correct for nonbracketing sera and estimate the cumulative incidence of infection from the serological data and surveillance data in Hong Kong.

RESULTS

We analyzed 4,843 sera from 2,097 unvaccinated participants in the study, collected from April 2009 to December 2010. After accounting for nonbracketing, we estimated that the cumulative incidence of H1N1pdm09 virus infection was 45% (95% credible interval [CI] = 40%, 49%), 17% (95% CI = 13%, 20%), and 11% (95% CI = 6%, 18%) for children ages 0-18 years, adults 19-50 years, and older adults >50 years, respectively. Including all available data substantially increased precision compared with a simpler analysis based only on sera collected at 6-month intervals in a subset of participants.

CONCLUSIONS

We developed a framework for the analysis of antibody titers that accounted for the timing of sera collection with respect to influenza activity and permitted robust estimation of the cumulative incidence of infection during an epidemic.

Plasma therapy against infectious pathogens, as of yesterday, today and tomorrow

Plasma therapy consists in bringing to a patient in need – in general suffering a severe, resistant to current therapy, and even lethal infection – plasma or specific, fractioned, antibodies, along with other immunoglobulins and possibly healing factors that can be obtained from immunized blood donors; donors (voluntary and benevolent) can be either actively immunized individuals or convalescent persons. Plasma therapy has been used since the Spanish flu in 1917–1918, and regularly then when viral epidemics threatened vulnerable populations, the last reported occurrence being the 2013–2015 Ebola virus outbreak in West Africa. The precise action mechanism of plasma therapy is not fully delineated as it may function beyond purified, neutralizing antibodies.

Cross species influenza: emerging zoonosis

Emerging infection is usually an important public health concern. Within the past decade, there are many new emerging infectious diseases. An important concern is on the pandemic of those new emerging infections. The cross species infection from animal to human, zoonosis, is usually problematic and hard to manage. The well-known situations are on new emerging atypical influenza infections. In this brief article, the author discuss on three important cross species emerging influenza, H5N1 bird flu, H1N1 swine flu and H7N9 bird flu. The basic details of those new influenzas genetic aberration and the concept for surveillance and prediction of new mutation that result in the new cross species emerging zoonosis are also mentioned in this article.

Association between antibody titers and protection against influenza virus infection within households

BACKGROUND

Previous studies have established that antibody titer measured by the hemagglutination-inhibiting (HAI) assay is correlated with protection against influenza virus infection, with an HAI titer of 1:40 generally associated with 50% protection.

METHODS

We recruited index cases with confirmed influenza virus infection from outpatient clinics, and followed up their household contacts for 7-10 days to identify secondary infections. Serum samples collected from a subset of household contacts were tested by HAI and microneutralization (MN) assays against prevalent influenza viruses. We analyzed the data using an individual hazard-based transmission model that adjusted for age and vaccination history.

RESULTS

Compared to a reference group with antibody titers <1:10, we found that HAI titers of 1:40 against influenza A(H1N1) and A(H3N2) were associated with 31% (95% confidence interval [CI], 13%-46%) and 31% (CI, 1%-53%) protection against polymerase chain reaction (PCR)-confirmed A(H1N1) and A(H3N2) virus infection, respectively, while an MN titer of 1:40 against A(H3N2) was associated with 49% (95% CI, 7%-81%) protection against PCR-confirmed A(H3N2) virus infection.

CONCLUSIONS

An HAI titer of 1:40 was associated with substantially less than 50% protection against PCR-confirmed influenza virus infection within households, perhaps because of exposures of greater duration or intensity in that confined setting.

Epidemiological characterization of influenza A(H1N1)pdm09 cases from 2009 to 2010 in Baguio City, the Philippines

Background

Baguio City, Philippines experienced its first influenza A(H1N1)pdm09 [A(H1)pdm09] case in May 2009. In spite of numerous reports describing the epidemiological and clinical features of A(H1)pdm09 cases, there are no studies about A(H1)pdm09 epidemiology in the Philippines, where year-round influenza activity was observed.

Objectives

We aimed to investigate the epidemiological and clinical features of A(H1)pdm09 in pandemic and post-pandemic periods.

Methods

Data were collected under enhanced surveillance of influenza-like illness (ILI) and severe acute respiratory infection (SARI) from January 2009 to December 2010. RT-PCR was used to detect A(H1)pdm09, following the protocol of the United States Centers for Disease Control and Prevention. The reproduction number was computed as a simple exponential growth rate. Differences in proportional and categorical data were examined using chi-square test or Fishers’ exact test.

Results and Conclusions

The outbreak was observed from week 25 to 35 in 2009 and from week 24 to 37 in 2010. The highest proportion of cases was among children aged 5–14 years. The number of ILI outpatients was 2.3-fold higher in 2009 than in 2010, while the number of inpatients was 1.8-fold higher in 2009. No significant difference in gender was observed during the two periods. The clinical condition of all patients was generally mild and self-limiting, with only 2 mortalities among inpatients in 2009. The basic reproduction number was estimated as 1.16 in 2009 and 1.05 in 2010 in the assumption of mean generation time as 2.6 days. School children played a significant role in facilitating influenza transmission.

Effectiveness of antiviral prophylaxis coupled with contact tracing in reducing the transmission of the influenza A (H1N1-2009): a systematic review

BACKGROUND

During the very early stage of the 2009 pandemic, mass chemoprophylaxis was implemented as part of containment measure. The purposes of the present study were to systematically review the retrospective studies that investigated the effectiveness of antiviral prophylaxis during the 2009 pandemic, and to explicitly estimate the effectiveness by employing a mathematical model.

METHODS

A systematic review identified 17 articles that clearly defined the cases and identified exposed individuals based on contact tracing. Analysing a specific school-driven outbreak, we estimated the effectiveness of antiviral prophylaxis using a renewal equation model. Other parameters, including the reproduction number and the effectiveness of antiviral treatment and school closure, were jointly estimated.

RESULTS

Based on the systematic review, median secondary infection risks (SIRs) among exposed individuals with and without prophylaxis were estimated at 2.1% (quartile: 0, 12.2) and 16.6% (quartile: 8.4, 32.4), respectively. A very high heterogeneity in the SIR was identified with an estimated I2 statistic at 71.8%. From the outbreak data in Madagascar, the effectiveness of mass chemoprophylaxis in reducing secondary transmissions was estimated to range from 92.8% to 95.4% according to different model assumptions and likelihood functions, not varying substantially as compared to other parameters.

CONCLUSIONS

Only based on the meta-analysis of retrospective studies with different study designs and exposure settings, it was not feasible to estimate the effectiveness of antiviral prophylaxis in reducing transmission. However, modelling analysis of a single outbreak successfully yielded an estimate of the effectiveness that appeared to be robust to model assumptions. Future studies should fill the data gap that has existed in observational studies and allow mathematical models to be used for the analysis of meta-data.