Influenza: epidemic activity with decreasing trend, but incidence increased

The epidemic activity of influenza is on a downward trend in Portugal, according to the Instituto Nacional Doutor Ricardo Jorge (INSA), despite the rise in the incidence of influenza syndrome to 34.6 per 100,000 inhabitants.

According to the flu epidemiological surveillance bulletin for the period from May 2 to 8 (week 18), the incidence rate of acute respiratory infection (ARI) followed the rise and also rose to 34.6 per 100,000 inhabitants (8 .0 in the previous week).

According to INSA, two cases of influenza (Influenza A) were reported in the week under analysis by the 17 Intensive Care Units (ICU). One of the patients was between 75-84 years old and the other between 35-44 years old. One of the cases had comorbidities and was vaccinated against seasonal flu.

Since the beginning of the season, 28 cases of influenza have been reported by the ICUs that collaborate in surveillance, all due to Influenza A virus.

As for the wards that communicated information, 19 cases of influenza were reported and in all cases the Influenza A virus was identified.

In the 2021/2022 season, the laboratories of the Portuguese Network of Laboratories for the Diagnosis of Influenza (Hospitals) reported 102,350 cases of respiratory infection and 6,599 cases of flu were identified.

In the week between May 2 and 8, 357 positive cases for the flu virus were identified, of which 356 were type A and 1 were type B, according to the bulletin.

So far, 141 cases of co-infection with the influenza virus and SARSCoV-2 have been detected.

In the bulletin, INSA also says that since the beginning of the 2021/2022 season, other respiratory agents have been identified in 5,335 cases. In week 18/2022, 172 cases were detected.

In total, until the 18th week (May 2nd to 8th), 204 influenza viruses were characterized, all with antigenic characteristics that differ from the virus included in the 2021/2022 influenza vaccine.

Influenza vaccination started in Portugal at the end of September, earlier than usual due to the covid-19 pandemic, and more than 2.5 million people were vaccinated.

The INSA bulletin also mentions that mortality from all causes is “within expectations for this time of year”.

Regarding the European situation, INSA reports that in week 17 (April 25 to May 1) several countries in the central and western part of the European region had a laboratory detection rate of the flu virus above 30%: Finland (80%), Netherlands (60%), Poland (50%), Serbia (38%) and France (33%).