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Two Phases of Infection Discovered in Patients with Severe COVID-19 Pneumonia

In This Article

  • By analyzing autopsied material from 24 COVID-19 patients, researchers at Massachusetts General Hospital have identified two phases of infection in severe COVID-19 pneumonia
  • The early phase is defined by high levels of virus in the lungs, while in the later phase, the virus is no longer present, but damage to lungs is too severe for recovery
  • David T. Ting, MD, said the findings indicate that patients' immune systems are able to attack SARS-CoV-2, but variable responses make it difficult to develop a "one-drug-fits-all" therapy approach

New research led by investigators at Massachusetts General Hospital has revealed two phases of infection in patients with severe COVID-19 pneumonia. Their findings could help improve treatment strategies for infected patients.

The group examined autopsied material from 24 patients who succumbed to COVID-19 and used a method called RNA in situ hybridization to visualize the SARS-CoV-2 virus in lung specimens.

They report that in the early phase of infection in patients with severe COVID-19 pneumonia, there are high levels of virus in the lungs that trigger patients' cells to express genes involved with the interferon pathway, a critical part of the immune response. In the later phase, the virus is no longer present, but the damage to the lungs is too severe for recovery.

David T. Ting, MD, associate clinical director for Innovation at the Massachusetts General Hospital Cancer Center and co-author of the study, said the interferon response to SARS-CoV-2 indicates that people's immune systems can attack the virus. However, the response is highly variable between patients, making it difficult to develop a single therapeutic approach, and treatments like remdesivir, which target viral replication, may only be effective in the early phase.

The team also found that there is surprisingly very little viral replication in the lungs, which suggests that the virus is mostly replicating in the nasal passages and then dropping into the lungs, where it can cause pneumonia and other complications.

Further research is necessary to better understand the extent and timing of SARS-CoV-2 infection in the lungs and other tissues, which could lead to improved treatment strategies for patients with COVID-19.

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