  Early detection of person-to-person transmission of emerging infectious
diseases such as avian influenza is crucial for containing pandemics. We
developed a simple permutation test and its refined version for this purpose. A
simulation study shows that the refined permutation test is as powerful as or
outcompetes the conventional test built on asymptotic theory, especially when
the sample size is small. In addition, our resampling methods can be applied to
a broad range of problems where an asymptotic test is not available or fails.
We also found that decent statistical power could be attained with just a small
number of cases, if the disease is moderately transmissible between humans.
