Influenza is a contagious respiratory illness caused by influenza viruses. It infects the nose, throat, and lungs commonly known as flu. The influenza has various types and sub-types infecting both humans and animals. Humans are infected throughout the year by some sub-types of Influenza virus, known as seasonal Influenza and has the potentiality to cause deadly pandemics.

WHO initiated National Influenza Centers (NICs) in many of its member countries as measures for early detection of pandemic threats by intense monitoring of the changes of types and sub-types as well as vaccine development. In 2007, IEDCR was recognized by WHO as the NIC of Bangladesh. IEDCR is also the national reference laboratory for influenza. Influenza surveillance is conducted through two systems:

1. NISB (National Influenza Surveillance Bangladesh), coordinated by IEDCR was initiated in 2010, and. It is conducted in 10 sentinel sites across Bangladesh, of which, 8 are district hospitals and 2 are medical college hospitals (Table 2).

2. HBIS (Hospital Based Influenza Surveillance) started in 2007, and is coordinated by IEDCR and icddr,b. It is conducted in 9 sentinel sites located in tertiary-hospitals of which 8 are government medical college hospitals and 1 is a private medical college hospital (Table 2).

Participants are recruited from the pediatric and medicine departments of the sentinel sites. Two types of cases are recruited: a) Severe Acute Respiratory Infections (SARI); b) Influenza like illness (ILI). ILI cases from out-patient departments and SARI cases from in-patient departments are selected using the case definition presented in Text Box 1. Nasal and throat swabs are collected from each of the enrolled cases and transported to IEDCR and icddr,b laboratories on weekly basis and tested for influenza A & B with reverse transcription polymerase chain reaction (RT-PCR). Weekly laboratory and epidemiological data are submitted to WHO Global Influenza Surveillance and Response System.

By utilizing this system two more surveillances are running:

1. SARS Cov-2 surveillance started from January, 2020 and

2. Respiratory Syncytial Virus surveillance running through integrated surveillance system where children under five years of age are recruited (started from October 2022)

In Bangladesh, the influenza season is from April to September which coincides with the monsoon season. The seasonal peak is in June and July. The number of sample collection increased as the number of sentinel sites increased over time.  The frequency of flu strains changed from year to year (Fig 1).

Highlights:

• Age group: Positivity rate amongst persons aged 15 to 25 years is the highest among all the age groups (From 2007 to 2023).

For further details, please click the link below:

-- https://www.iedcr.gov.bd/site/page/077670e7-ea37-439e-a59e-085d4c49e923/-

-- https://www.iedcr.gov.bd/site/page/55f17e29-d56d-4d6e-aa35-129000fdb9da/-