Global factors are speeding up the spread of these diseases and public health needs to get in front.
Respiratory viruses keep evolving and we must and can prepare for future outbreaks, says Professor Hazel Clothier, lead epidemiologist at SAEFVIC (Surveillance of Adverse Events Following Vaccination In the Community).
Professor Clothier told delegates at the Immunisation Coalition’s Annual Scientific Meeting held in Victoria this week that the combination of climate change, globalisation and human behaviour were accelerating the spread of respiratory diseases, requiring improved surveillance, vaccine innovation and global coordination.
The big three – covid, flu and RSV – tend to be front of mind, but data shows continual change in the soup of infection circulating around the globe, such as the rise of whooping cough in our area, and the continual presence of other coronaviruses like OC43, which can cause big problems in aged care.
Factors driving virus spread
Climate change is a huge factor in the evolving spread of disease, with long-term climate changes, meteorological factors like rising temperatures, and extreme weather events affecting ecological and socioeconomic mechanisms that in turn affect biological mechanisms which flow on to virus emergence, human infection and disease transmission and can lead to a pandemic.
Respiratory viruses are not all seasonal. Most respiratory viral infections can be influenced by climate drivers, and there are wide regional differences that we don’t fully understand, Professor Clothier explained.
For example, outbreaks of enterovirus D68, a mild-to-severe respiratory disease, were rare until 2008, probably because warmer temperatures extended seasonal activity. In 2014, Finland and the US had severe infections in children.
The virus was interrupted by covid but has been reappearing since 2022, particularly across Europe, with new lineages emerging. “It’s definitely going to be one to watch in 2025, although we haven’t had much in Australia as yet.”
Zoonotic spillover
Around three-quarters of emerging diseases are zoonotic in origin.
“We really need to start thinking about the animal-human interface that we’re developing and the strategies that we can have for managing that,” said Professor Clothier.
Bird flu is the current one of concern. Climate change has affected bird migration and increased spread, but there are also theories about the impact on mixing of bird flocks, the impact on the bird host and the viral ecology.
“These things are not simple. They are multicomplex,” said Professor Clothier.
H5N1 is now in mammals and it is evolving, which will affect our behaviours around interaction with animals, including pets, she said. Data on spread between cats and people, which was posted briefly on the CDC website on Wednesday last week, has since disappeared.
Australia is the only continent right now that doesn’t have H5N1 cases (apart from the single traveller case in Victoria last year).
Urbanisation and travel
Travelling is popular across all age groups, which increases contact between reservoir species. Our population keeps growing and the majority live in cities, which are high-risk environments, said Professor Clothier.
As we urbanise, we come into more contact with more reservoir species. “It’s not just the people that like to come together, it’s also the viruses,” said Professor Clothier.
We’re more likely to see viruses like human adenovirus 55 (HAdV-55), which often occurs as a co-infection, is very virulent and can cause severe pneumonia. It is endemic in China and South Korea, but there’s not much data elsewhere yet. It’s currently “one to watch”, she said.
Another example is bocavirus, first noted in 2005, which may have a role in superinfections.
The last mile
The effects of climate change, like temperature change and extreme weather events, also affect pandemic control by making storage, transportation and stability of vaccines harder. It affects the “last mile”, said Professor Clothier.
Urbanisation has its upside when it comes to vaccination, she said: “The capacity for surveillance and control programs, our prevention and public health knowledge programs are far better in cities where we can come together and work together.”
This is along with access to treatment and vaccination.
“And the global response that we can have – maybe, if everybody is participating in it – and the support that we could give, although it is a changing world, would be easier to deliver,” she said.
