On December 2nd, the CDC provided options to reduce the quarantine period for those who have been exposed to SARS-CoV-2, the virus that causes the illness COVID-19. The purpose of the options is to reduce the amount of time that people must stay home from work, and also, the options may lessen the stress on the public health system. This update results from increased knowledge of the SARS-CoV-2 incubation period, infectious period, and effective testing window.
The CDC continues to endorse a quarantine of 14 days after the last known contact with a person infected with the virus, but now offers alternative, shorter options:
A person who is exposed to SARS-CoV-2 but who remains asymptomatic may quarantine for 10 days instead of 14, without testing.
Alternatively, a person may quarantine for only 7 days after exposure to SARS-CoV-2 if that person remains asymptomatic and receives a negative test result. The negative test result must occur on or after the fifth day of quarantine.
Because regional public health departments make the final decisions regarding length of quarantine, the revised CDC quarantine options may or may not be adopted by every region and institution.
The CDC guidelines regarding isolation of patients who are known to be infected with SARS-CoV-2 remain the same:
Isolate at least 10 days from the onset of symptoms, and at least 24 hours with no fever without fever-reducing medication. Isolation can then be discontinued, but only if Covid-19 symptoms are improving. One exception is that loss or distortion of taste and smell may persist for weeks or months, but the patient does not need to remain in isolation or quarantine during recovery of those senses.
Those with severe Covid-19 illness that require hospitalization and those with weakened immune systems may need to isolate for 20 days after the onset of symptoms. This period of time is flexible, depending on the discretion of the patient’s doctor and the local health department.
If a person has tested positive for SARS-CoV-2 and has recovered from Covid-19 symptoms, that person should wait a minimum of three months before testing for the virus again, unless symptoms of Covid-19 develop again. (This does not preclude a person from serology testing during that time, to look for evidence of antibodies to the virus, as opposed to testing for an active viral infection.)
The CDC guidelines align with what scientists and doctors have learned about the incubation period and infectious period of the SARS-CoV-2 virus, the duration of illness that this virus causes, Covid-19, and the effective testing window of time.
Most SARS-CoV-2 infections can be detected by PCR or antigen testing by the fifth day after infection.
Most people infected with SARS-CoV-2 who become symptomatic will develop symptoms before the seventh day of exposure.
Most people infected with SARS-CoV-2 are not infectious beyond 10 days after the onset of Covid-19 symptoms. (Exceptions include immunocompromised individuals and those with severe disease.)
It is not uncommon to continue to test positive for SARS-CoV-2 for an extended time after infection, because non-infectious viral particles may remain at detectable levels in the body for weeks or months after infection. Unless a person has an immune system deficiency, a positive test result within three months after infection does not mean that person is still infectious to others. Most likely, a person with a positive test result within three months of infection is not infectious to others and doesn’t need to quarantine unless symptoms reappear.
Immunity to SARS-CoV-2 is hypothesized to last at least one year in healthy individuals who are not immunocompromised. This estimate is based upon the known length of immunity to SARS-CoV-1.
SARS-CoV-2 is the coronavirus that causes the disease Covid-19.
Covid-19 is the disease that is caused by the SARS-CoV-2 virus.
Quarantine: A person who has been exposed to the SARS-CoV-2 virus must quarantine to stay away from others. Quarantine after exposure to SARS-CoV-2 is most commonly done at home.
Isolation: A person who is infected with the SARS-CoV-2 virus must isolate to stay away from others, even those living with them at home.
The quarantine update can be found at the CDC website here.
The isolation information can be found at the CDC website here.