"Drink plenty of fluids": argument was not convincing.

Editor—I am not convinced by the paper by Guppy et al that drinking fluid is harmful to all patients with respiratory infection.1 Thinking that increased secretion of antidiuretic hormone secretion in infections of the lower respiratory tract is a common phenomenon is not correct. Hyponatraemia is a well known complication of infections of the lower respiratory tract, but it is not common. Furthermore, it is difficult to prove whether the incidence or the death of patients with hyponatraemia related to infections of the lower respiratory tract was associated with increased water intake. Hyponatraemia could still occur even with normal fluid intake. Fluid restriction may not be helpful to all infections of the lower respiratory tract. To restrict fluid to the extent of causing dehydration may even be harmful. The authors' data cannot be extrapolated to patients with upper respiratory infection because there was no definite evidence. In Hong Kong the newspapers quoted the study and said that plenty of fluid in flu can be harmful. I worry that the community might have a misconception about the findings of this study.