The earlier inflammatory and wound healing signals (i.e. IL-1 and MMP 9) and lack of Mx responses in Penobscot strain fish were associated with higher survival to co-infection compared to Saint John strain families, however, Penobscot strain families also exhibited inherently greater resistance to ISAv compared to Saint John strain families regardless of single ISAv or co-infection with sea lice. The gene discussed is MX1; the disease is coinfection.