Global monitoring of influenza: potential contribution of national networks from a French perspective

COVID-19 in comparison with other emerging viral diseases: risk of geographic spread via travel

PURPOSE OF REVIEW

The COVID-19 pandemic poses a major global health threat. The rapid spread was facilitated by air travel although rigorous travel bans and lockdowns were able to slow down the spread. How does COVID-19 compare with other emerging viral diseases of the past two decades?

RECENT FINDINGS

Viral outbreaks differ in many ways, such as the individuals most at risk e.g. pregnant women for Zika and the elderly for COVID-19, their vectors of transmission, their fatality rate, and their transmissibility often measured as basic reproduction number. The risk of geographic spread via air travel differs significantly between emerging infectious diseases. COVID-19 is not associated with the highest case fatality rate compared with other emerging viral diseases such as SARS and Ebola, but the combination of a high reproduction number, superspreading events and a globally immunologically naïve population has led to the highest global number of deaths in the past 20 decade compared to any other pandemic.

Influenza vaccine effectiveness among healthcare workers in comparison to hospitalized patients: A 2004-2009 case-test, negative-control, prospective study

The objective of this study was to calculate Vaccine Effectiveness (VE) in healthcare workers (HCW) and to compare VE between patients and HCW. A case-control investigation based on the prospective study was conducted between 2004 and 2009 in a teaching hospital. All HCW with influenza-like illness (ILI) from participating units (n = 24) were included, and vaccination status was characterized by interview. A total of 150 HCW presented ILI; 130 (87%) were female, 27 (18%) were positive for influenza, and 42 (28%) were vaccinated. Adjusted VE was 89% (95% CI 39 to 98). Among patients, adjusted VE was 42% (95% CI -39 to 76). The difference of VE (VEhcw - VEpat) was 46.15% (95% CI 2.41 to 144). The VE ratio (VEhcw / VEpat) was 2.09 (95% CI -1.60 to 134.17). Influenza VE differed between HCW and patients when the flu season was taken into account. This finding confirms the major impact of host determinants on influenza VE.

Influenza epidemiology and characterization of influenza viruses in patients seeking treatment for acute fever in Cambodia

The epidemiology, symptomology, and viral aetiology of endemic influenza remain largely uncharacterized in Cambodia. In December 2006, we established passive hospital-based surveillance to identify the causes of acute undifferentiated fever in patients seeking healthcare. Fever was defined as tympanic membrane temperature >38°C. From December 2006 to December 2008, 4233 patients were screened for influenza virus by real-time reverse-transcriptase polymerase chain reaction (rRT–PCR). Of these patients, 1151 (27·2%) were positive for influenza. Cough (68·8%vs. 50·5%,P<0·0001) and sore throat (55·0%vs. 41·9%,P<0·0001) were more often associated with laboratory-confirmed influenza-infected patients compared to influenza-negative enrollees. A clear influenza season was evident between July and December with a peak during the rainy season. Influenza A and B viruses were identified in 768 (66·3%) and 388 (33·7%) of the influenza-positive population (n=1153), respectively. In December 2008, passive surveillance identified infection of the avian influenza virus H5N1 in a 19-year-old farmer from Kandal province who subsequently recovered. From a subset of diagnostic samples submitted in 2007, 15 A(H1N1), seven A(H3N2) and seven B viruses were isolated. The predominant subtype tested was influenza A(H1N1), with the majority antigenically related to the A/Solomon Island/03/2006 vaccine strain. The influenza A(H3N2) isolates and influenza B viruses analysed were closely related to A/Brisbane/10/2007 or B/Ohio/01/2005 (B/Victoria/2/87-lineage) vaccine strains, respectively. Phylogenetic analysis of the HA1 region of the HA gene of influenza A(H1N1) viruses demonstrated that the Cambodian isolates belonged to clade 2C along with representative H1N1 viruses circulating in SE Asia at the time. These viruses remained sensitive to oseltamivir. In total, our data suggest that viral influenza infections contribute to nearly one-fifth of acute febrile illnesses and demonstrate the importance of influenza surveillance in Cambodia.

Strategies to improve global influenza surveillance: a decision tool for policymakers

BACKGROUND

Global pandemic influenza preparedness relies heavily on public health surveillance, but it is unclear that current surveillance fully meets pandemic preparedness needs.

METHODS

We first developed a conceptual framework to help systematically identify strategies to improve the detection of an early case or cluster of novel human influenza disease during the pre-pandemic period. We then developed a process model (flow diagram) depicting nine major pathways through which a case in the community could be detected and confirmed, and mapped the improvement strategies onto this model. Finally, we developed an interactive decision tool by building quantitative measures of probability and time into each step of the process model and programming it to calculate the net probability and time required for case detection through each detection pathway. Input values for each step can be varied by users to assess the effects of different improvement strategies, alone or in combination. We illustrate application of the tool using hypothetical input data reflecting baseline and 12-month follow-up scenarios, following concurrent implementation of multiple improvement strategies.

RESULTS

We compared outputs from the tool across detection pathways and across time, at baseline and 12-month follow up. The process model and outputs from the tool suggest that traditional efforts to build epidemiology and laboratory capacity are efficient strategies, as are more focused strategies within these, such as targeted laboratory testing; expedited specimen transport; use of technologies to streamline data flow; and improved reporting compliance. Other promising strategies stem from community detection - better harnessing of electronic data mining and establishment of community-based monitoring.

CONCLUSION

Our practical tool allows policymakers to use their own realistic baseline values and program projections to assess the relative impact of different interventions to improve the probability and timeliness of detecting early human cases or clusters caused by a novel influenza virus, a possible harbinger of a new pandemic. Policymakers can use results to target investments to improve their surveillance infrastructure. Multi-national planners can also use the tool to help guide directions in surveillance system improvements more globally. Finally, our systematic approach can also be tailored to help improve surveillance for other diseases.