**1. Introduction**

The low pathogenicity avian influenza (LPAI) H9N2 virus is the most widespread subtype in poultry around the world, posing a concern for animal and public health [1]. Despite their low pathogenicity, H9N2 avian influenza viruses (AIV) are causing heavy economic losses, particularly during coinfection with other respiratory pathogens [2, 3]. Globally, the virus has become endemic in multiple regions of the world counting Asia, the Middle East, and Africa [4]. On the African continent, the first A(H9N2) outbreak was reported in Libya in 2006 [5, 6], then in Egypt in late 2010 [7]. Even though many studies later showed that the virus was present in the country earlier, cocirculating with highly pathogenic avian influenza viruses (HPAIV) of the

H5N1 and H5N8 subtypes have been associated with heavy economic losses in the poultry industry [2, 8–10]. Since then, many African countries started surveillance programs for influenza viruses in poultry and the emergence of G1 lineage H9N2 viruses has been documented. LPAI H9N2 viruses emerged in Tunisia in December 2009 leading to the circulation of the disease in many parts of the country [11]. Rapidly spread in the African continent, the disease has been declared in Morocco in early 2016 [12], then in Algeria in late 2017 showing more than 99% genetic and antigenic similarities with Moroccan strains [13]. Since then, the virus started to spread southward making its way to several Sub-Saharan countries: it was first detected in Burkina Faso in 2016 [14], in Ghana in 2018 [15], and it expanded to Togo, Benin, Uganda, Kenya, Nigeria between 2017 and 2020 and Senegal, with a human case reported in 2020 (**Figure 1**) [16–19].

LPAI H9N2 has not only been detected in poultry but also in some human cases, being a real threat to human health and a global concern for public health. Thus, different studies showed that circulating H9N2 strains acquired an affinity to mammalian like-receptors and gained high virulence and pathogenicity through amino acid substitutions in their viral proteins [11, 12]. Human infections with LPAIV H9N2 have so far been reported in just two African countries; Egypt with four cases, since 2015 [20] and recently Senegal with a case in a 16-month-old child [17]. To date no report of AIV H9N2 in poultry in Senegal is available. Finally, it has been reported that LPAIV H9N2 can easily undergo genetic reassortment and donate internal gene segments to HPAIV H5 and H7 [21, 22].

#### **Figure 1.**

*Phylogenetic spectrum of H9N2 lineage in African countries. The emergence of G1-West lineage is shown in green reported in poultry and some humane cases (figure created with www.mapchart.net).*
