No country in the world has done more controversial virus-tinkering research than America.

A first-of-its-kind study analyzed 'gain-of-function' experiments - which involve making pathogens more infectious or deadly - performed globally since 2000.

Advocates say the tests help science get ahead of future outbreaks, but critics say the risks of a leak outweigh any potential benefit.

The study found there have been more than 7,000 GOF or loss of function studies - which make viruses weaker - in the past two decades, with the US involved in more than half, followed by China (21 percent).

Many scientists believe Covid was the product of a leak from the Wuhan Institute of Virology in China, where scientists were carrying out gain-of-function experiments on bat coronaviruses closely related to Covid using American research grants.

The study, conducted by researchers at Georgetown University's Center for Security and Emerging Technology, used artificial intelligence to scan 159,000 scientific literatures to find where and how often GOF and LOF studies are conducted. 

They found approximately 7,000 studies included this type of research and randomly chose 1,000 to manually sort through, leaving them with 488 publications. 

Of this literature, 25 percent involved only GOF work, 29 percent involved both GOF and LOF and 46 percent involved only LOF research.