Corona Virus-Airborne transmission and How Long immunity lasts

The Science indicates that even 2 meters may not be enough unless you wear

a face mask.

Covid19 transmission and immunity

International Journal of Environmental Research and Public Health — Open Access Journal

Airborne Transmission Route of COVID-19: Why 2 Meters/6 Feet of Inter-Personal Distance Could Not Be Enough

The COVID-19 pandemic caused the shutdown of entire nations all over the world. In addition to mobility restrictions of people, the World Health Organization and the Governments have prescribed maintaining an inter-personal distance of 1.5 or 2 m (about 6 feet) from each other in order to minimize the risk of contagion through the droplets that we usually disseminate around us from nose and mouth. However, recently published studies support the hypothesis of virus transmission over a distance of 2 m from an infected person. Researchers have proved the higher aerosol and surface stability of SARS-COV-2 as compared with SARS-COV-1 (with the virus remaining viable and infectious in aerosol for hours) and that airborne transmission of SARS-CoV can occur besides close-distance contacts. Indeed, there is reasonable evidence about the possibility of SARS-COV-2 airborne transmission due to its persistence into aerosol droplets in a viable and infectious form. Based on the available knowledge and epidemiological observations, it is plausible that small particles containing the virus may diffuse in indoor environments covering distances up to 10 m from the emission sources, thus representing a kind of aerosol transmission. On-field studies carried out inside Wuhan Hospitals showed the presence of SARS-COV-2 RNA in air samples collected in the hospitals and also in the surroundings, leading to the conclusion that the airborne route has to be considered an important pathway for viral diffusion. Similar findings are reported in analyses concerning air samples collected at the Nebraska University Hospital. On March 16th, we have released a Position Paper emphasizing the airborne route as a possible additional factor for interpreting the anomalous COVID-19 outbreaks in northern Italy, ranked as one of the most polluted areas in Europe and characterized by high particulate matter (PM) concentrations. The available information on the SARS-COV-2 spreading supports the hypothesis of airborne diffusion of infected droplets from person to person at a distance greater than two meters (6 feet). The inter-personal distance of 2 m can be reasonably considered as an effective protection only if everybody wears face masks in daily life activities.

It is not known how long immunity will last. But booster shots and yearly flu shots are examples

of dealing with this issue.

Can You Catch Covid-19 Twice?

Most scientists say patients gain some immunity to the virus after the first infection

A sample drawn from a patient at a Covid-19 testing site in Houston on June 28.

PHOTO: DAVID J. PHILLIP/ASSOCIATED PRESS

By 

Updated July 8, 2020 10:02 am ET

o                                          PRINT

o      Months into the pandemic, the scientific community’s understanding of Covid-19, the illness caused by the new coronavirus, is rapidly evolving. New reports of patients testing positive, or appearing to suffer symptoms after initial diagnosis, continues to generate concern that people who have had Covid-19 are getting infected anew.

Here is the latest on what we know, and don’t know, about the possibility of becoming sick with the virus more than once.

I recently recovered from Covid-19. Does that mean I can’t get it again?

Most scientists say that people who have had Covid-19 gain some immunity to the virus that causes it. What they don’t know is whether that protection lasts a few months, a few years or a lifetime.

What factors affect immunity?

The immune system wards off infections by producing antibodies that fight invaders. A range of hereditary and environmental factors, including diet and sleep patterns, typically affect the strength and longevity of those defenses.

Immunity also depends on the pathogen. For example, infection by the virus that causes measles confers lifelong immunity. Others, like the influenza virus, can mutate so rapidly that protective antibodies might not recognize them during a reinfection.

The novel coronavirus mutates more slowly than the influenza virus. That gives researchers hope that any natural immunity, or vaccine, would offer more lasting protection. Even if someone gets sick again, researchers believe a second infection might be milder than the first.

How soon would my body produce antibodies to fight the novel coronavirus after an initial infection?

The U.S. Centers for Disease Control and Prevention says antibodies develop within one to three weeks after infection.

A study involving 34 hospitalized cases in China found that two patients, both in their 80s, produced antibodies within three days of symptom onset. The rest produced them two weeks after symptoms first surfaced. The findings were vetted by other experts and published in an academic journal in March.

Is there any good news?

A group of Chinese researchers reported this month that they had infected six rhesus macaques, allowed them to recover and then reinfected four of them 28 days after the first infection. None became sick again, showing their immune system shielded them from a second infection.

The research, published in Science, says, however, that more studies are needed to understand whether the immune system can shield individuals from reinfection over longer periods of time.

Then why are some people testing positive again?

Roughly 450 South Koreans tested positive for the virus again after meeting the criteria for recovery and being discharged from isolation. The Korea Centers for Disease Control and Prevention re-tested more than half of those people and found no evidence of the live virus circulating.

Peer-reviewed research studies have shown that viral fragments can circulate even after an individual is symptom-free. That doesn’t mean that people are still sick or infectious.

How do I know I’ve fully recovered?

Clinicians have mixed views on what constitutes recovery because long-term data aren’t yet available. Guidelines vary across the globe.

For example, the CDC says that infected individuals are considered recovered if they test negative for the novel coronavirus twice, with tests approved by the U.S. Food and Drug Administration taken at least 24 hours apart.

Or, individuals must be fever-free for three consecutive days and show an improvement in their other symptoms, including reduced coughing and shortness of breath. At least 10 days should have passed since their symptoms first surfaced.

Some survivors testing negative for the virus say that certain symptoms, such as a loss of taste and smell, can linger for months after other symptoms are gone.