H10N3 bird flu human case: Top expert says world will find more 'unusual examples' of viruses in humans in wake of COVID-19

A leading Kiwi epidemiologist says the world can expect to find more "unusual examples" of viruses jumping between animals and humans due to "intense scrutiny" of people with respiratory illnesses in the wake of COVID-19.

It comes after China recorded what is believed to be the first-ever human case of infection from the rare bird flu strain H10N3. The 41-year-old infected man was hospitalised in April and then diagnosed with H10N3 on May 28. He's in a stable condition and ready to be discharged.

The Chinese National Health Commission hasn't found any other cases of the virus in the man's close contacts and says the risk of large-scale transmission is low. No other cases have been found worldwide. 

Professor Michael Baker, an epidemiologist at the University of Otago, says the human case of H10N3 is "interesting", but from the report he's read, it appears to be of little risk. 

"The report was fairly reassuring about the level of risk here but we know viruses do evolve rapidly and no one is going to say there is zero risk of ongoing transmission, but it is probably very low," he told Newshub.

Dr Baker said the report emphasises that the strain has "relatively low pathogenicity", meaning its "ability to cause harm". 

"It's one of the strains of virus that is isolated in poultry but the risk of spreading on a large-scale is considered low. It is not a common virus."

He believes the world will likely see more "unusual" cases of viruses jumping to humans as populations more intensely scrutinise respiratory illnesses. 

"One of the things that we are seeing more often is that there is such intense scrutiny on human respiratory illness and very vigorous testing that we are seeing more of these unusual examples of viruses that have jumped the species barrier, so we say they are spillover cases from animal reservoirs to humans.

"The big test is do they go anywhere. Usually, the answer is no. Humans are known as dead-end hosts because it crosses over, it may cause a mild illness in humans, or even a serious illness or even kill people sometimes, but we don't transmit it. It is not really very well adapted to humans or transmission between humans.

"The more we look, the more we will find examples like this."

There's heightened awareness of different illnesses in the wake of the COVID-19 pandemic, which was first recorded in China in late 2019. 

"I think it is also interesting that this was detected in China. China has been a success story with eliminating COVID-19. There is now, of course, a huge scrutiny in China of people with respiratory illness to do what New Zealand is doing, which is to pick up outbreaks of COVID-19 early," Dr Baker said. 

"They will be looking very vigorously with a population of 1.4 billion people. So this is obviously one of the places we would find one of these unusual examples of transmission from an animal or bird reservoir to humans."

While there are various strains of avian influenza found in China, which sometimes infect people, Reuters reports there has been no significant number of human infections since 2016/17, when the strain H7N9 killed 300 people.