As a PhD student, Sander studied vaccination strategies against human metapneumovirus, which causes severe respiratory disease in children and the elderly, defending his thesis in 2008. As a postdoc, he explored the pathogenicity and transmissibility of the pH1N1 virus during the 2009 pandemic, identifying key virulence factors and new antiviral drug resistance markers. He extensively researched the genetic and phenotypic traits that allow avian H5N1, H7N9, and H10N8 influenza viruses to transmit through the air among mammals, focusing on the anatomical sites in the respiratory tract involved in airborne transmission. Sander also contributed to studies on the pathogenesis of SARS-CoV-2 in macaques and investigated an intranasal prophylactic treatment to reduce its transmission. His group was the first to demonstrate that SARS-CoV-2 can be transmitted via the air over distances greater than one meter. In response to the high demand for face masks during the SARS-CoV-2 pandemic, he supervised a collaborative project to test the filtration efficiency of locally produced masks for coronavirus using custom experimental setups. His research has significantly advanced understanding of viral transmission and infection control measures.