The most transmissible variant yet of the coronavirus is threatening a fresh wave of infections in New Zealand. The sub-variant of Omicron known as BA.5 is reported as now dominant in the United States, and is likely to make up the majority of community cases here within a couple of weeks.
BA.5 is considered to be probably 40 to 50 percent more transmissible than the BA.2 variant, responsible for the majority of our cases to date. The WHO says global reported Covid-19 cases are up 30 percent in the last two weeks driven by BA.4 and BA.5 waves.
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United States National Institute of Allergy and Infectious Diseases director Dr Anthony Fauci has been the chief medical adviser to both presidents Biden and Trump.
He told Saturday Morning it was difficult to predict the end of the increasingly infectious variants of Omicron.
"One thing that this virus has consistently shown us is that it continues to evolve and mutate, and with some mutations not all, it leads to a different variant. And when the variant has a transmission advantage over the prior variant that's when you get increase in infections like we're seeing here in the United States and others throughout the world.
"As long as there's a lot of activity of virus throughout the world, and we don't get reasonably good control over the replication dynamics of the virus, that will always give the virus the opportunity to replicate. And the more you replicate, the greater chance there is of mutating and the more you mutate, the greater chance there is of getting a new variant."
He said it came down to controlling the virus to reduce the possibility of new variants.
Fauci said vaccinations and boosters protected against "severe disease" and hospitalisations, but not so much against infection itself.
Drugs like Paxlovid suppressed the virus, but it did not kill it.
"Almost invariably people who get reinfected, get reinfected with a strain a little bit different than the original strain that infected them. And the new strain tends to evade, partially, the immune protection that the original infection conferred upon you."
Covid-19 could be treated as equivalent to the flu when community infection was low enough and did not disrupt social order, he said. "Namely, it doesn't cause the fear, the disruption of the economy, the disruption of our social interactions, the way it has done over the last two and a half years. We're not there yet.
"I'm sure that coronavirus will be with us for quite a while, maybe indefinitely, so we're going to have to deal with the fact that this virus does change and create new variants."
As for Long Covid, he said there were no answers yet as to why some people suffered from it while others do not.