Hello and welcome to HCM A fall in both white blood cell count and platelet count indicate s a viral infection. Other causes include sever bacterial infection. Rheumatoid arthritis is also known to cause a fall in both WBCs and platelets. I would also like to know your RBC counts and status of lymphocytes. If RBC count is also low then other causes of bone marrow depression have to be sought. In case lymphocytes are activated, then chances of viral infection are more. Further serological tests need to be done for other viral infections. This depends on the region where you are staying because epidemics of viral infections vary from place to place. For eg Dengue fever is more prevalent in urban areas and people who have recently visited urban areas, rickettsial infection is more common in rural areas & country side. So, all these factors have to be kept in mind and the urther investigations has to be ordered by your treating physician. Thank you and take care Dr Shailja P Wahal