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Are COVID-19 Patients Infectious for up to 90 Days After Recovery?

Published on Oct 16, 2020   -  6 min read



There have been reports of recovered COVID-19 patients getting reinfected and testing positive for almost 3 months. Read the article to know more about reinfections and immunity.


An increasing number of recovered COVID-19 patients are allegedly reporting back to hospitals with lingering COVID-19 symptoms, such as difficulties in breathing and chest pain. Some patients, apparently asymptomatic, keep testing positive long after recovering. Such patients are in a dilemma if they should end their quarantine and come out, or if they are still capable of infecting others.

The other most confusing topic is reinfection with the SARS-CoV-2 virus. There have been reports of COVID-19 recovered patients testing positive and showing symptoms again. This has resulted in a lot of questions about immunity and antibodies against this new Coronavirus. But, most health authorities state that reinfection is not possible in the first three months after recovery. Then why do so many patients keep testing positive?

With the scarcity of COVID-19 testing, not everyone who initially tests positive receives follow-up testing. And according to CDC guidelines (U.S. Centers for Disease Control and Prevention), isolation is ended based on how the patient feels after ten days of onset of symptoms and not on retesting. And there is still confusion about what a positive follow-up test means.

What Are the Current Guidelines for Isolation of COVID-19 Patients?

CDC, on 3rd August 2020, updated the guidelines for isolation because of increased reports of people continuing to test positive for up to 3 months and not being infectious to others. The latest results suggest that retesting in the three months after the initial infection is unnecessary unless the patient exhibits symptoms of COVID-19, and all other causes have been ruled out. This does not mean that a person is immune to reinfection with SARS-CoV-2 in the three months following infection.

COVID-19 patients should be isolated:

  1. At least ten days after the onset of symptoms.

  2. 24 hours after the patient no longer has a fever without the use of antipyretic medicines.

Various studies have been performed to determine the length of infection, the period of viral shedding, the possibility of asymptomatic spread, and the risk of spread based on the patient's other health conditions. These studies suggested that the number of live viruses in the nasal cavity and throat significantly drops after the symptoms develop. Also, most COVID-19 patients were no longer infectious ten days after symptoms began. Only severely ill and immunocompromised people continued to be contagious for as long as 20 days.

Should Recovered COVID-19 Patients Get Retested Before Ending Isolation?

According to the CDC, isolation can be ended if you do not have any symptoms, and it has been ten days since the onset or if you did not have a fever in the last 24 hours without using medicines. The point to be noted is that loss of smell and taste might last for several months and will not influence the end of isolation. A negative test is not required to be around others for most people. If your doctor asks you to get tested again to see if you are still infectious, please repeat the test.

These recommendations do not apply to people with severe COVID-19 or extremely weak immune systems.

When Can Immunocompromised or Severely Ill COVID-19 Patients Be Around Others?

Recovered immunocompromised or critically ill COVID-19 patients might have to stay home in isolation for up to 20 days. Such patients might have to get retested before their isolation ends.

What Do We Know So Far About COVID-19 Reinfection?

To date, we do not have enough information available that supports reinfection with the SARS-CoV-2 virus. Data do show that people who have recovered from COVID-19 may harbor low levels of the SARS-CoV-2 virus in their bodies for as long as three months after diagnosis. So, some recovered people will continue to test positive the next three months even if they do not necessarily transmit the infection to others.

As of now, no confirmed reports show reinfection with COVID-19 within three months of primary infection. But more research is needed. This is why the CDC advises recovered patients with new symptoms to get evaluated for reinfection. If you develop influenza-like symptoms after recovering from COVID-19, make sure you isolate yourself and consult your doctor for the possible causes and if retesting is needed.

Current Findings That Do Not Support Reinfection:

  1. The concentrations of the new Coronavirus reduces significantly in the nasal cavity and throat after the onset of symptoms.

  2. The capacity of the virus to replicate decreases after the onset of symptoms. In mild to moderately sick COVID-19 patients, viruses capable of replicating and spreading have not been recovered after ten days following the start of symptoms. Only in some severely ill and immunocompromised individuals, viruses capable of replicating have been documented between 10 and 20 days after onset of the symptoms.

  3. One study demonstrated that people with a positive contact did not get infected if the exposure to the infected person started 6 days or more after the person's illness onset.

  4. A study conducted by CDC in Korea, where 285 patients who persistently tested positive, including 126 patients that again developed COVID-19 symptoms, showed that they did not infect their 790 contacts. And scientists were unable to isolate replication-competent viruses (viruses that can replicate) from 108 of these patients.

Current Findings That Might Indicate Reinfection:

  1. In a study conducted on workers of a nursing facility to see the future of asymptomatic patients, 1 out of the 48 staff members showed a positive result more than 20 days after the primary diagnosis.

  2. In another reported case, a mildly infected patient tested positive for replication-competent virus around the 18th day after symptom onset.

After Recovering, Are COVID-19 Patients Immune?

When a virus attacks the body's cells, the immune system gets activated, which sends cells to fight the virus off. These immune cells also send signals to warn other cells by releasing proteins called interferons. Interferons signal neighboring cells to prepare to fight the virus off. But the SARS-CoV-2 virus blocks these interferons. So, the immune system gets activated, but the cells in the body do not become defensive. So the virus keeps replicating in the cells of the lungs and goes deeper.

As the immune system gets activated, it does produce antibodies against the virus, and survivors of COVID-19 did show high levels of antibodies to the virus. However, some people showed very low levels of antibodies in their blood. So, recovered COVID patients cannot be considered immune, and more studies have to be conducted to determine immunity to reinfection by this virus, even up to 3 months of infection.

How Long Do Antibodies to COVID-19 Last?

A recent UK study found that immunity against COVID-19 could decline within months. Almost 60 % of the patients in the study demonstrated a potent antibody response; only 17 % retained the same levels of antibodies three months later. And in some cases, it became completely undetectable. This means people can still get reinfected during seasonal waves of the SARS-CoV-2 virus, and it is possible that vaccines may not provide long-term protection. This also contradicts the theory of herd immunity.

Why Do Some COVID-19 Patients Continuously Test Positive After Recovery?

In some recovered patients, the detection of viral RNA through reverse transcription-polymerase chain reaction (RT-PCR) in the throat swab can give positive results. Scientists claim that these are just viral particles left behind after the active infection. There is no proof still available that suggests that these viral particles can replicate and infect others.

Is It Conclusive That Recovered COVID-19 Patients Who Test Persistently Positive Are Not Contagious?

Even though the detected viral RNA in recovered patients is low in concentration, and it is unlikely that such people can infect others, there is no hard and fast rule in medicine. Although no evidence supports such a spread, there still might be a chance that a minimal percentage of such recovered patients who keep testing positive might still be contagious.

If a Recovered COVID-19 Patient Is Identified as a Contact of a New Case, Should They Be Tested or Quarantined?

According to the CDC, if the patient recovered from COVID-19 less than three months back and had a positive contact in that period, then retesting and quarantine is not needed. But, if it is more than three months, then the patient should be quarantined and tested.


While there are contradictory findings of the viral genetic material found in patients after the time window to be able to replicate and be contagious, most doctors suggest it is not a possibility for recovered patients to be contagious after the initial 10 to 20 days. But, some doctors are warning their patients about the possibility of extremely rare cases where immunocompromised and severely ill but recovered patients may still be contagious. This makes us wonder if the guidelines for how long the Coronavirus lasts in the body should be changed. Such recovered people might act as reservoirs for the virus and potentially cause local outbreaks later on. Even though there is no proof, there is still a minute chance of that happening.

So, until we have more data or a vaccine, it is essential to continue safety precautions, such as physical distancing, masks, and frequent hand hygiene, to control the spread of the virus.


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16 Oct 2020  -  6 min read


Dr. Shyam Kalyan N

Dr. Shyam Kalyan N

MBBS (Madras Medical College), DLO, DNB

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