  Effective, sensitive, and reliable diagnostic reagents are of paramount
importance for combating the ongoing coronavirus disease 2019 (COVID-19)
pandemic at a time there is no preventive vaccine nor specific drug available
for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It would be
an absolute tragedy if currently used diagnostic reagents are undermined in any
manner. Based on the genotyping of 7818 SARS-CoV-2 genome samples collected up
to May 1, 2020, we reveal that essentially all of the current COVID-19
diagnostic targets have had mutations. We further show that SARS-CoV-2 has the
most devastating mutations on the targets of various nucleocapsid (N) gene
primers and probes, which have been unfortunately used by countries around the
world to diagnose COVID-19. Our findings explain what has seriously gone wrong
with a specific diagnostic reagent made in China. To understand whether
SARS-CoV-2 genes have mutated unevenly, we have computed the mutation ratio and
mutation $h$-index of all SARS-CoV genes, indicating that the N gene is the
most non-conservative gene in the SARS-CoV-2 genome. Our findings enable
researchers to target the most conservative SARS-CoV-2 genes and proteins for
the design and development of COVID-19 diagnostic reagents, preventive
vaccines, and therapeutic medicines.
