The Centers for Disease Control and Prevention is still waiting on samples to conduct important research, the newspaper reports, citing confirmations from the National Security Council and the World Health Organization. China and other governments have previously committed to sharing samples of strains with pandemic potential "in a timely manner." Previously, the process had become routine, according to the newspaper.

Andrew C. Weber, a former Pentagon official managing biological defense, told the publication the country's refusal to send samples is "scandalous" and that many people "could die needlessly if China denies international access to samples."

The NIH has said the H7N9 strain currently doesn’t transmit easily between humans. But if it mutates to be easily transmissible, H7N9 has pandemic potential because most people have little to no immunity. To date, the strain has killed 39% of people who have become infected, according to the agency. 

Dr. Larry Kerr, the HHS’ director of pandemics and emerging threats, told the Times the process of sending and receiving viral samples normally takes several months. But due to the recent trade dispute between the U.S. and China, experts worry there could be a further delay in shipments.