Recently, the “zombie deer” virus has attracted attention. What is the “zombie deer” virus? What impact does it have on human health? The Beijing CDC WeChat public account publishes relevant popular science knowledge.
Beijing Disease Control and Prevention pointed out that “zombie deer” are manifestations of prion-infected animals. Although they are called viruses, prions are essentially proteins that can infect a variety of animals (sheep, cattle, deer, camels, etc.) and humans.
Prion disease is a type of degenerative disease caused by prions (abnormally shaped proteins) that invades the central nervous system of humans and various mammals. It has a long incubation period and a 100% fatality rate. In terms of types, prion diseases suffered by humans are mainly divided into Creutzfeldt-Jakob disease (sporadic, hereditary, iatrogenic, variant, CJD), kuru, Gerstmann syndrome (GSS), Fatal familial insomnia (FFI). The incidence of human prion diseases in most developed countries is 1-1.5 cases per million people per year.
Among human prion diseases, 80%-95% are sporadic Creutzfeldt-Jakob disease. The average survival period of sporadic Creutzfeldt-Jakob disease is about 6 months, 85%-90% of patients die within 1 year, and the peak age of onset is 55-75 years old.
Taking Creutzfeldt-Jakob disease as an example, Beijing Disease Control and Prevention pointed out that human infection with prion diseases is mainly divided into three mechanisms: spontaneous (sporadic CJD), hereditary (hereditary CJD) and acquired (iatrogenic). Type Creutzfeldt-Jakob disease, variant Creutzfeldt-Jakob disease). 85-90% of cases of Creutzfeldt-Jakob disease are sporadic.
Specifically, in sporadic CJD, the conversion of normal prion protein (PrPC) into pathological prion (PrPSc) is thought to occur spontaneously (or possibly through somatic mutation of PRNP); in hereditary CJD Creutzfeldt-Jakob disease is more likely to come from genes carried by families that are more susceptible to mutations in the prion protein gene PRNP; iatrogenic Creutzfeldt-Jakob disease occurs due to iatrogenic methods such as infected corneal transplants and electroencephalogram depth electrodes; mutated Creutzfeldt-Jakob disease Creutzfeldt-Jakob disease, the only human prion disease known to be transmitted directly from animals to humans, is caused by the consumption of beef products infected with mad cow disease.
Because the lesions mainly occur in nerve cells, most cases of Creutzfeldt-Jakob disease will manifest as progressive dementia, pyramidal/extrapyramidal dysfunction, visual or cerebellar disorders, etc.
The gold standard for diagnosis of Creutzfeldt-Jakob disease is the detection of PrPSc protein in the brain tissue of patients. Because brain tissue samples are difficult to obtain, they can generally only be collected after the patient dies. Clinically, it is mainly based on the patient’s clinical manifestations, electroencephalogram changes, magnetic resonance changes, and pathological changes to jointly determine whether the patient is a clinically diagnosed case of Creutzfeldt-Jakob disease.
While some symptoms of human prion diseases can be temporarily treated, unfortunately, three randomized, double-blind, placebo-controlled trials failed to change disease outcomes, and there is currently no cure. According to domestic patient follow-up data, most patients died within 6 months of onset.