CD40LG and malaria: Furthermore, because the patient had no history of exposure to HFRS endemic areas, exposure to an HTNV-infected rodent, or a positive HTNV-IgG test, and false serological tests of IgM can be caused by various factors, the HFRS coinfection with malaria was ruled out.<h4>Conclusion</h4>Misdiagnosis can be easily induced by a false serological test, in particular the IgM test which can be influenced by various factors.