Influenza viruses continue to show intense activity in the community and its positivity, according to the latest report of the EODY, remains above 10%, (seasonal threshold for the onset of epidemic influenza activity according to the European Center for Disease Control and Prevention (ECDC) .

Since the start of influenza surveillance, 85 people with laboratory-confirmed influenza have been hospitalized in the ICU, 84 (99%) with influenza A and one (1%) with influenza B, and 25 deaths from influenza have been recorded. Influenza type A virus was isolated from 24 (96%) cases and influenza type B virus from 1 (4%). Six of the 24 strains were subtyped and belonged to subtype A(H1)pdm09.

Type A gives more severe clinical symptoms with more patients hospitalized in ICU, according to experts.

The APE-MPE addressed the experts of the Pasteur Institute for the surveillance of the epidemics caused on an annual basis by the influenza virus.

Pasteur Institute: National Influenza Reporting Laboratory of Southern Greece

The Southern Greece Influenza Reporting Laboratory is located at the Hellenic Pasteur Institute and, under the scientific supervision of Dr. E. Angelakis, Biopathologist, Research Director and the technical guidance of Dr. M. Emmanuel, Biologist, Special Functional Scientist, is active in laboratory investigation and surveillance of epidemics caused on an annual basis by the influenza virus. It is recognized by the World Health Organization (WHO) and a member of the European ERLI-Net Network and the WHO GISRS International Influenza Virus Surveillance System.

Based on data from the Influenza Reference Laboratory of Southern Greece for this year’s surveillance period, the seasonal flu, which is 92% due to the influenza virus A(H1N1pdm09) showed a strong upward trend in early January, with a positivity rate of 38% in representative community sample during the 2nd week of the year.

The longitudinal monitoring of the disease in Greece by the National Reference Laboratories shows that seasonal influenza activity ranges from October to May, and usually peaks during the months of January-February-March. From 2023, at European level, influenza surveillance will now take place throughout the year.

Influenza Surveillance

The National Influenza Reference Laboratory of Southern Greece accepts a representative number of samples from primary and secondary care providers (private practitioners, health centers and hospitals) and is responsible for the surveillance of circulating influenza strains in the country, in collaboration with the National Influenza Reference Laboratory of Northern Greece Greece.

Circulating strains are subtyped at the Influenza Reference Laboratory, and a subset of these are tested each year at the genetic and antigenic level to characterize influenza strains, as well as their susceptibility to antiviral drugs. The data collected by the Reference Laboratory is used to monitor the strains circulating in the country, to detect mutated or resistant strains early and to select the strains that will make up the next year’s influenza vaccine recommendation by the World Health Organization.

From the beginning of October until the first week of January, 215 strains of influenza have been typed, derived from hospital samples and from samples from Community Health Centers (Sentinel Morbidity Surveillance Network), of which 99% were type A and 1% type B. Overall, of the type A strains subtyped 8% belonged to subtype A(H3N2) and 92% to subtype A(H1N1)pdm09.

During the 1st week of January, the influenza subscription index showed an increase compared to the previous ones. An increase was recorded in the age groups, 0-4, 15-64 and over 65 years. In all the samples taken by the laboratory observers of the Sentinel network, the positivity of the influenza virus reached 43%. During the 2nd week of surveillance, influenza virus positivity was 38%, while a small decrease in cases was observed in all age groups.

Vaccination and Vaccine Efficacy

Influenza is a contagious respiratory disease caused by the influenza virus that can cause mild to severe acute respiratory infection. The elderly, young children and people with chronic illnesses are more at risk of serious complications from the flu. The flu virus is spread from one person to another through small, invisible droplets and through contact with contaminated surfaces. Factors such as cold weather and crowding increase the contagiousness of influenza.

The main way to protect oneself from the flu is timely vaccination, the two scientists emphasize. No drug can replace the flu shot, which is the main prevention measure for the flu, they note.

“When the flu viruses in the vaccine are similar to the viruses that are circulating this season, it is very effective. The data resulting from the characterization of the strains circulating in each country are sent by the National Influenza Reference Laboratories to the World Health Organization in order to make decisions about the next year’s vaccine recommendation. In the elderly and those with serious chronic diseases the vaccine is often less effective, but even in these cases it reduces hospital admissions and deaths from complications. In this winter season, the use of enhanced anti-influenza vaccines serves to better immunize vulnerable groups against the influenza virus.”

The vaccines available against influenza viruses include 4 strains of influenza, A(H3N2), A(H1N1), B(Victoria), B(Yamagata), and belong to the following categories:

prepared by incubation in chicken eggs (15mcg of each antigen)

cell cultures (similarly)

* High dose quadrivalent inactivated vaccine (60 mcg of each antigen)

* Quadrivalent inactivated influenza vaccine with MF59 adjuvant (15mcg of each antigen + adjuvant).

“Preliminary results of genetic and antigenic characterization of circulating strains at the European level show a high correlation of the vaccine with the H1N1pdm09 strain, which is so far prevalent in the community. A correspondingly high correlation is also shown by the type B strain, which is expected to show an increase after March. The coverage of the vaccine against the H3N2 strain, which circulates in low percentages in the community, appears to be lower,” notes Mr. Angelakis.

Overall, there seems to be a good correlation of this year’s vaccine with the circulating strains, but we will have more complete data by collecting aggregate data after the epidemic wave of influenza is over, he concludes.