Thrombocytosis at an early stage of respiratory tract viral infection.

Aim: To determine whether thrombocytosis, a platelet count of more than 500 x 10 9 /l, occurs at an early stage of respiratory tract viral infection. Methods: The medical records of 345 patients with respiratory syncytial virus (RSV), influenza, measles, adenovirus or human herpes virus 6 infections were retrospectively reviewed. Results: The mean platelet count was significantly higher in RSV patients than in patients with other respiratory infections. Among the 29 patients with thrombocytosis, 24 (82.8%) had RSV infection. Conclusion: When thrombocytosis is positive at an early stage of respiratory tract infection, RSV should be taken into account as a causative agent.