Understanding COVID-19 Reactivation and Its Neurological Impact
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Overview of COVID-19 Reactivation
Recent reports indicate a worrying trend in COVID-19 reactivations. In South Korea, over 200 individuals who had previously recovered tested positive for SARS-CoV-2 again. According to the Korea Centres for Disease Control and Prevention (KCDC), the reactivated virus seems to exhibit “little or no infectivity.”
In an April correspondence with the American Journal of Infection Control, Chinese doctors revealed that seven patients, previously discharged, tested positive once more for SARS-CoV-2 via quantitative RT-PCR. Symptoms upon reactivation commonly included cough and fever, but were generally less severe than during the initial infection.
A small study published in the Journal of Infection involving 55 discharged patients found that about 9% were readmitted due to symptoms such as fever, fatigue, cough, and sore throat, ultimately testing positive for SARS-CoV-2 again. The authors noted, “Evidence suggests a segment of recovered COVID-19 patients may reactivate.”
Research from Switzerland, after analyzing two re-admitted patients, concluded that reinfection seems unlikely, attributing the reactivation to the stringent recovery criteria enforced in South Korea compared to other nations.
Potential Links to the Nipah Virus
In a letter to Transboundary and Emerging Diseases, Kevin Roe, a semi-retired researcher from San Jose State University, presented insights about COVID-19 reactivation by drawing parallels with the Nipah virus. This bat-derived virus, noted for its outbreaks in Asia, also causes respiratory and neurological symptoms.
Roe highlighted that both SARS-CoV-2 and the Nipah virus are RNA enveloped viruses originating from bats, leading to similar neurological manifestations such as headaches, seizures, and brain inflammation (encephalitis). Notably, the CDC reported that neurological symptoms can re-emerge in approximately 8% of Nipah virus survivors months or years after exposure due to reactivation in neurons.
Concerns About Neuropsychiatric Effects
Psychiatrists are raising questions about the potential neuropsychiatric consequences following COVID-19 infection. They ponder, “Are we facing a surge of neuropsychiatric sequelae due to COVID-19?”
Why Neurons are Targeted
Roe explained that viruses like COVID-19 and Nipah selectively infect neurons because these cells lack MHC proteins necessary for alerting the immune system. This allows viral replication to go unnoticed, creating an ideal environment for the virus to persist.
Similar to HSV-1, which establishes latency in neurons to evade immune detection, SARS-CoV-2 might also hide within the nervous system. Research suggests that human coronaviruses can linger in the central nervous system, potentially leading to pathological consequences in some individuals while remaining subclinical.
Triggers for Virus Reactivation
The reactivation of viruses like HSV-1 is often triggered by external immunosuppressive factors, primarily psychological stress that raises cortisol levels, which can weaken the immune system. Other stressors include fatigue, hormonal fluctuations, and prolonged UV exposure, among others.
“In most cases, reactivation does not lead to serious disease,” remarked Bjørn Grinde, a Norwegian expert in genetics and evolution. Fortunately, the reactivations of COVID-19 observed have generally been milder than the initial infections.
Conclusion
In summary, the emergence of neurological symptoms in COVID-19 patients suggests that SARS-CoV-2 can infect neurons and may remain dormant, potentially reactivating later with reduced symptoms. Comparisons with related viruses like Nipah, HSV-1, and human coronaviruses bolster this theory. Whether COVID-19 infection leads to a life-long condition remains to be seen.
Fortunately, strategies exist to mitigate or prevent such latent virus reactivations. Maintaining physical fitness has proven beneficial, as demonstrated by astronauts dealing with social isolation. Additionally, managing psychological stress and other immunosuppressive factors can be advantageous.
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