The physical space of the MSK Library is permanently closed to visitors as of Friday, May 17, 2024. Please visit this guide for more information.
The physical space of the MSK Library is permanently closed to visitors as of Friday, May 17, 2024. Please visit this guide for more information.
COVID-19 (coronavirus disease 2019) is a disease caused by a virus named SARS-CoV-2 and was discovered in December 2019 in Wuhan, China. It is very contagious and has quickly spread around the world.
COVID-19 most often causes respiratory symptoms that can feel much like a cold, a flu, or pneumonia. COVID-19 may attack more than your lungs and respiratory system. Other parts of your body may also be affected by the disease.
People with COVID-19 have had a wide range of symptoms reported – ranging from mild symptoms to severe illness. Symptoms may appear 2-14 days after exposure to the virus. Anyone can have mild to severe symptoms.
Possible symptoms include:
This list does not include all possible symptoms. Symptoms may change with new COVID-19 variants and can vary depending on vaccination status.
Look for emergency warning signs* for COVID 19:
Anyone infected with COVID-19 can spread it, even if they do NOT have symptoms.
COVID-19 commonly spreads when an infected person breathes out respiratory droplets or very small particles that contain the virus. These droplets and particles can be breathed in by other people or land on their eyes, noses, or mouth. In some circumstances, they can land on surfaces and survive for periods of time, depending on the type of surface. The virus can then spread when someone else touches a surface contaminated by the virus.
The smallest of these particles can stay suspended in the air for for significant time -- minutes to even hours depending on the environment -- before falling to the ground. In outdoor environments, or spaces with high levels of ventilation,t he circulation of fresh air disperses these drifting droplets quickly, and so the combination of wearing face coverings and maintaining physical distance (6 feet or more) is very effective at impeding the spread of COVID-19. However, in indoor spaces, especially those with poor ventilation, coronavirus-laden droplets can build up to a level that is risky.
Respiratory transmission occurs when infectious agents are carried from an infected person's nose or mouth via coughing, sneezing, or through saliva and mucous. This type of transmission requires close but not necessarily direct contact with an infected person. If an infected person coughs or sneezes on or near you the respiratory droplets can either enter directly into the nose or mouth or land on unwashed hands and spread.
Airborne transmission occurs when infectious agents (bacteria, viruses, etc) are carried in the air via aerosols (long-lasting particles). This type of transmission leads to extremely contagious diseases, since it requires no close contact with an infected person. Simply being in the same room as in infected individual can lead to infection.
Formite transmission involves inanimate objects that are contaminated with an infectious agent. This can be things like doorknobs, telephones, handrails. Formites are usually nonporous hard surfaces that infectious agents can stay on until they are disinfected.
Reinfection with the virus that causes COVID-19 means a person was infected, recovered, and then later became infected again. After recovering from COVID-19, most individuals will have a short time-period with some protection from repeat infections. However, reinfections commonly do occur after COVID-19. We are still learning more about these reinfections. Ongoing studies of COVID-19 are helping us understand:
SARS-CoV-2 RNA can persist for many weeks in the respiratory tract of individuals that have recovered clinically from COVID-19, though the period with which the virus can be isolated in symptomatic patients is likely considerably shorter. The persistence of viral RNA in compartments has been primarily measured from the different compartments that shed virus or are easily accessible including the respiratory tract, gastrointestinal tract, and the blood.
The course of infection in cases with moderate or severe disease who recover from the acute phase appears to be very heterogeneous. In the majority of patients, recovery is prompt and relatively fast. However, various epidemiological studies indicate that over one third of patients do not recover completely at 14–21 days post‐infection, and some of them remain symptomatic for several months.
A cohort study of 1,832 US adults published in January 2023 in JAMA Network Open, found that "participants had a higher risk of health care encounters related to pulmonary, diabetes, neurological, and mental health diagnoses 6 months after infection compared with their pre–COVID-19 baseline, even after controlling for COVID-19 severity and other risk factors, and participants who reported more severe initial illnesses were more likely to have 28 or more days of symptoms. In addition, unvaccinated participants were at higher risk of 28 or more days of symptoms and of medical encounters associated with pulmonary and neurological diagnoses."
There is also a third category of infection course, where patients with COVID‐19 infections initially appeared to have recovered from the acute viral infection but nevertheless progressed in their disease and eventually died. These patient continued to express negative on molecular tests for SARS‐CoV‐2 RNA, so while it appears that they cleared the virus in the nasal tract (where PCR tests are administered), the virus was clearly sill persisting in other organs, including deep in the lung tissue, brain, and other organs, leading to disease progression and subsequent death.
A November 2022 study in Nature carried out complete autopsies of 44 patients who died of COVID-19, including extensive tissue sampling throughout the central nervous system. The team concluded that "we show that SARS-CoV-2 is widely distributed, predominantly among patients who died with severe COVID-19, and that virus replication is present in multiple respiratory and non-respiratory tissues, including the brain, early in infection. Further, we detected persistent SARS-CoV-2 RNA in multiple anatomic sites, including throughout the brain, as late as 230 days following symptom onset in one case. Despite extensive distribution of SARS-CoV-2 RNA throughout the body, we observed little evidence of inflammation or direct viral cytopathology outside the respiratory tract. Our data indicate that in some patients SARS-CoV-2 can cause systemic infection and persist in the body for months."
A March 2023 study published in the Journal of Pathology conducted post‐mortem (autopsy) analyses of "27 consecutive patients who had apparently recovered from COVID‐19 but had progressively worsened in their clinical conditions despite repeated viral negativity in nasopharyngeal swabs or bronchioalveolar lavage for 11–300 consecutive days. These patients revealed frequent, long‐term presence of virus‐infected cells in specific lung structures, including bronchial glands and cartilage. Thus, the progressive worsening of clinical conditions in apparently PCR‐negative patients after COVID‐19 is often associated with the persistent infection of specific cell types in the lung."