Polio: the evolution of the virus vs eradification

one of the problems of using an attenuated virus is that by giving a mild case of the disease, there is a danger that the virus will evolve back into the severe disease. This is rare but a problem with the oral polio vaccine.

the danger ironically is not to the kid who got the vaccine, but to those around them who didn't get one of the polio vaccines: Usually in the US among religious groups that won't vaccinate or in the third world, where the religious leaders read the conspiracy theories and told their people not to get it.

IN other words, the problem with the anti vax movement is not that these essentially healthy people can't get away with their delusions and exaggerations of risk, but that others misinterpret their misinterpretation and so kids die.

so the CDC has a report about the world wide eradification of polio:

Global efforts have led to the eradication of two of the three wild poliovirus (WPV) serotypes (types 2 and 3), with only WPV type 1 (WPV1) remaining endemic, and only in Afghanistan and Pakistan...

I always wondered how they decided this, since many cases in these countries never see a doctor. Well, the public health people monitor sewage.

but the bad news: The polio virus that evolved from the weakened vaccine is spreading: Maybe because more kids didn't get their vaccinations during covid, or because they were told it was dangerous, so the number of people who don't have any immunity to polio has increased:

The number of polio cases caused by circulating vaccine-derived polioviruses (cVDPVs; circulating vaccine virus strains that have reverted to neurovirulence) decreased from 881 in 2022 to 524 in 2023; cVDPV outbreaks (defined as either a cVDPV case with evidence of circulation or at least two positive environmental surveillance isolates) occurred in 32 countries in 2023

sigh.