[3] The aim of these research studies was to understand when, how and why globally important pathogens emerged and caused disease, and [to] "provide advice on how to prevent the spread to humans".

[8] Hayman contributed to a 2012 study that explored the fertility, mortality and migration of the Straw-coloured fruit bat (Eidolon helvum) in Ghana because of their proximity to humans and evidence of possible infection with zoonotic viruses.

The research showed that E. helvum were widespread across sub-Saharan Africa and that it was important to continue establishing demographic parameters to gain good understanding of potential dynamics.

[12] A study authored by Hayman in 2016 identified bats (order Chiroptera) as hosts of a range of viruses that can affect humans and be a threat to global security.

The spread of rhinolophid bats was mapped across the world and changes to ecological dynamics caused by human population increases and intervention such as removing forests, and high cropping and livestock density were examined.

Much of Hayman's work focused on developing integrated approaches to public health and environmental protection that could prevent infectious disease outbreaks as a potential threat to global security.

[15] Another article, written by Hayman in 2016, noted that the way the West African Ebola crisis had been managed gave cause for concern and the high fatality rate showed the need for the financing of improved healthcare infrastructures, particularly in vulnerable countries.

The paper co-authored by Hayman concluded that the work of the Australian team had provided useful models to build understandings of how bat-viral ecology interacts with anthropogenic change and the findings would help develop appropriate actions being taken "to mitigate the drivers of viral spillover".

[17] 2018 research in which Hayman collaborated, developed a model framework to assist in understanding how the effect of human encroachment into natural habitats was related to the emergence of novel infectious diseases.

[19] In 2019 Hayman co-authored a paper that acknowledged the considerable financial investment in infectious disease research but noted there were challenges in sharing scientific data before and during emergencies.

A paper, co-authored by Hayman, [described] "the epidemiologic and molecular investigation into the source and magnitude of the outbreak and discussed the public health response initiated to prevent similar events from occurring in the future".

[21] Hayman was part of team that researched the geographical distribution and spatial patterns of Cryptosporidiosis and Giardiasis within New Zealand to see if there were differences in variants within an island system and the rest of the world.

The research concluded that the species and variants found in an island were no different from other countries and this was most likely due to gene flow through widespread human travel and high numbers of cattle and people as host populations.

The paper concluded that DT160 was introduced into New Zealand on a single occasion from 1996 through 1998 and propagated across the country with evidence showing transmission between humans, poultry, cattle and wild birds as host groups.

[24] In a further interview for Radio New Zealand Hayman reiterated that while it was not fully established the disease had come from bats or snakes, it had been traced to Wuhan without any confirmation of the animal that had passed on the infection.

In the same interview he said this was frightening and could result in an overload on the health system, but the spread could be stopped if people acted responsibly by washing their hands and practicing [social distancing.

[27] As New Zealand moved from an elimination of the virus to a suppression approach, Hayman commented in October 2021 that this had not been totally effective in other countries and cited the United Kingdom which had high rates of infection and a strain on their health system.

[40][41] When the team was given clearance to go to China in January 2021 Hayman was unable to attend in person due to issues in getting a booking in managed isolation on his return to New Zealand, but continued to contribute to the work.

[44] Hayman, along with other members of the expert team, was one of the co-authors of an article in Nature in August 2021 that urged further action on getting key scientific studies to assist in determining the origins of SARs-CoV-2.

Referring to this research, Jamie Morton[47] in the New Zealand Herald noted: "What Dr David Hayman discovers could help us better understand how many of the worst infectious diseases on the planet – Ebola, HIV/Aids and pandemic influenza among them – transfer from their animal hosts.