As India is facing the COVID19 pandemic, one of the technical terms that is increasingly heard is ‘reverse quarantine’, a method of protecting vulnerable people from getting infection. This article discusses the potential merits of this concept, pertinent historical anecdotes and practical ways to implement it from India’s standpoint. Also discussed are herd immunity and the futility of making predictions at this stage of the pandemic.
What is the difference between quarantine and reverse quarantine?
When a person had a contagious illness, keeping him away from other healthy people was a method that was traditionally used in public health over centuries. This is called quarantine, or isolation. The objective is to physically prevent him from infecting the people around him, until he was no longer a threat.
Reverse quarantine is exactly the opposite. When a person is vulnerable and there is imminent danger of his getting infection from other sick people, he is kept away until the danger passes.
Why is reverse quarantine important in the case of COVID19?
Although highly contagious, the SARS-Cov2 virus affects people differently. Children and healthy young adults are less likely to become sick or die from the virus. Older people, particularly those with long-standing illnesses have significantly higher chance of dying from the infection. Limiting their exposure to the virus is the essence of reverse quarantine in this context.
In the absence of a vaccine or approved medication, the fight against this pandemic basically boils down to administrative and engineering strategies according to established principles of public health. We are already familiar with measures such as lockdown, social distancing, screening of overseas visitors and tracking and isolation of contacts.
As the pandemic spreads deeper into the community, reverse quarantine is one of the proposed solutions that is expected to keep vulnerable people safe. Apart from those over age 65, this includes people who have diseases of the lung, kidney, liver, heart or the immune system, diabetes and those with socioeconomic disadvantage.
In the absence of widespread testing, it is impossible to estimate the extent of spread of virus in any community; underreporting is a worldwide problem. India’s testing rates are still low. It must be kept in mind that in the case of this virus, absence of proof cannot be taken as proof of absence. Hence the case for taking every measure possible to protect the weak and the vulnerable.
Why is reverse quarantine not always feasible in the Indian setting?
In India, older people either live alone, or share the home with their children or extended family members. It is practically not possible to relocate older people in India into a secure isolation facility.
Even if that were possible, an outbreak could still occur at such a closed facility causing large number of deaths, as is widely being reported in the United states and in Toronto, Canada.
Homes in India are typically small, with several spaces being shared between family members. In addition, a large number of people live in slums and other tiny makeshift dwellings. It is not uncommon to find five or six people sharing a single room house. Caregivers of the elderly are invariably the other family members. Thus, there is greater chance of physical contact between people.
In other words, it is not always feasible to practice physical distancing in Indian homes. Although frequently heard during discussions, whether reverse quarantine could save lives in crowded settings like India remains to be proven. Some experts feel that spending time as a large group in a small closed space as part of lockdown could be riskier than sitting outside where there is natural ventilation.
The SARS-Cov-2 virus is known to rapidly spread within closed spaces, with aerosols being the most likely method. Aerosols behave like mist, being made of really tiny droplets that stay suspended in air and spread throughout the room. Aerosols can be generated even through normal conversation. Their dynamics are distinct from the heavy droplets generated by coughing, that fall on the ground within a six feet distance.
The tiny size of aerosol particles (median size is only 1 µ, much smaller than the traditional sneeze droplet of 50 µ) makes it easy for them to be inhaled directly into the lungs of other people present in the room. This is the likely mechanism by which COVID-19 superspreading events have occurred all over the world, with attack rates as high as 50-75%.
In other words, if someone in the household contracts the infection, it is not always possible to shield others from the virus—even if hands are washed and physical spacing is practised. Being a new virus, the lack of prior immunity allows the infection to literally rip through entire communities.
Thus, the practice of reverse quarantine in a typical crowded Indian home of low to middle income setting is not quite the same as that in a wealthy person’s mansion. Regardless, the following ten steps may be considered.
What are some of the methods that could work in India if there are vulnerable people at home?
1. Visitors must be minimised in places where older and other vulnerable people are living. This includes limiting visits by relatives, neighbours and socialites who come in contact with large numbers of people every day.
2. Each family member needs to do their bit to minimise the chance of bringing the virus into the household. Work from home option can help limit exposure of younger family members to potential sources of infection.
3. When there are vulnerable family members at home, healthcare professionals working in areas with high risk of infection, might wish to consider a temporary alternative dwelling, and return home after a period of self-quarantine.
4. Children habitually are close to their grandparents. It can be difficult to get children to follow all the norms of social distancing and hygiene. They could easily act as carriers of the virus into the household, without becoming sick themselves. Children may therefore be discouraged from mingling with kids from other homes, till the crisis is over.
5. For the designated caregiver, washing hands before and after providing physical assistance is an effective practical step.
6. Split or staggered meal timings is another way to reduce aerosol spread during conversation over a meal. Social isolation of the elderly should however be actively prevented; the use of mobile phones and other technology could help in that regard.
7. Keeping windows open to the extent possible will reduce the risk of the virus circulating in closed spaces.
8. For those who are wealthy and can afford a second home, the family could split temporarily so that there is geographical separation between the healthy and the vulnerable.
9. Treatment of chronic illnesses should not get neglected as a result of the family’s attention being focussed on COVID-19. Complications of such conditions can be difficult and expensive to treat. Telemedicine could be used instead of routine doctor visits, to minimise unnecessary trips to hospital.
10. Through administrative and engineering modifications, hospitals must try to keep elderly patients with chronic illness far away from the sections that treat fever and respiratory illnesses.
Reverse quarantine through history
As the lethal Spanish flu pandemic of 1918 spread quickly throughout the world, Commander John Martin Poyer who was the Governor of the Pacific island of East Samoa stood guard, preventing the entry of all individuals from outside. His action saved the lives of those on the island.
In contrast, the nearby island of West Samoa, under a different regime, was less assertive with implementing reverse quarantine. A ship called SS Talune that sailed from Auckland, was allowed to dock at West Samoa only after superficial quarantine measures. Unfortunately, that ship had passengers who had the influenza virus. A few of the ship’s passengers entered West Samoa. Flu spread rapidly through West Samoa.
Meanwhile, SS Talune was denied permission to dock at East Samoa by John Poyer as part of his reverse quarantine protocol.
The end result was that 8500 people died (one-fifth of the population) on the west Samoa island, compared to zero deaths on East Samoa.
This is a fine example of an uncompromising strategy of reverse quarantine saving an entire community. The community support that John Poyer received in implementing that strategy played a role too.
When will the pandemic end? Does reverse quarantine help with manipulating herd immunity?
It is generally believed that all pandemics naturally stop spreading when a certain number of people in the population become immune to the virus. The logic here is that once these thresholds are reached, the virus is no longer able to find a host to infect. As a result, transmission slows down and stops. The percentage of people who need to become immune can vary between viruses. For measles, a higher percentage need to be immune, while for influenza, the required percentage is lower.
This is the concept of herd immunity. It is defined as the proportion of individuals in a community who are immune to a disease. Herd immunity could also result from vaccination—as in the case of Polio. Herd effect refers to the indirect protection enjoyed by the remaining individuals in that community.
As there is no vaccination available for the SARS-Cov-2 virus, the only option to get herd immunity appears to be by getting the infection. Epidemiologists generally agree that large segments of the world’s population will eventually get infected, albeit at a slower rate due to active efforts at flattening the curve.
Dr Jayaprakash Muliyil, noted epidemiologist has put forward a proposal that if we were somehow able to pick the 55% who are required to become immune in a community, to try and exclude the elderly from it. That is because, in the process of getting herd immunity, a large number of people will die in the older age group. In contrast, the same process will cause considerably fewer deaths if an equal number of younger people were infected.
In addition, dependency on the hospital system is higher when older people get admitted with COVID-19. The likelihood of an elderly patient with COVID-19 requiring a hospital and ICU bed is higher, the stay is longer, yet the outcome is worse than in a younger patient.
Younger people move around more and are thus more likely to come into contact with the virus, and also to spread the virus. Therefore, it makes epidemiological sense that they get the first exposure to the virus and develop immunity as a group. The idea here is that the younger people build up the herd immunity, while the older individuals stay indoors and enjoy the herd effect, as discussed above.
While this might not be an exact science yet, the absence of a better alternative makes a strong case for pursuing the concept of reverse quarantine. By adopting a policy that limits social exposure for the vulnerable over an extended period of time, theoretically the herd immunity can be manipulated to include predominantly younger people.
Although this strategy leaves the older people vulnerable to illness, it can be hoped that by that time, a vaccine would become available.
Why is it not possible to make a long-term prediction? What are neutralising antibodies?
There are several things we do not know yet about the SARS-Cov-2 virus, that limit our ability to predict long-term outcomes.
Firstly, we cannot assume that those who were infected once with the virus will never get it again. The body’s response to each virus is different; and we don’t have long-term data on the SARS-Cov-2 virus yet. Besides, all the antibodies produced following an infection are not necessarily protective against future infection by the same virus.
Unless a specific class of antibodies called neutralising antibodies are produced, there will be no protection from future attacks. Simply put, if the body were a fortress and the virus was an invader, neutralising antibody is like the security guard who attacks and defeats the virus while it is still at the gates. Its role is to prevent the virus from gaining entry to the cells of the body.
Unfortunately, not all viral infections generate neutralising antibodies, and among those that do, not all cases get lifelong immunity. It is worth noting here that a vaccine becomes successful only if it is able to generate neutralising antibodies, which will last for a long time.
For instance, infection by some viruses like measles confer lifelong immunity, while others like SARSCov1 provide only two or three years of protection. Antibodies against the HCov OC43 and HCov HKU-1, the other coronaviruses that cause the common cold, provide immunity for less than a year.
Thus, the long-term outlook for immunity against COVID-19 depends on whether it generates neutralising antibodies, and also on how long the antibody levels remain protective. As in the case of influenza, COVID-19 flareups could occur when immunity levels fade, especially when public health measures slacken.
Secondly, we have limited understanding about its spread in crowded communities, and in varying weather conditions. Thirdly, we do not know to what extent the virus spreads within closed air circulation systems. Fourthly, we do not know the exact reasons why some people get only a mild illness, while others have a fulminant course. Specifically, we do not know why children do not get severe disease. Obtaining answers to these questions will boost our ability to prevent and treat disease, and also to predict long-term outcomes.
Vaccine development and trials for the new virus are ongoing, results are at least 18 months away. Not all viruses can be prevented by vaccine. For instance, viruses such as HCV and influenza have the ability to frequently change their antigens, which poses a challenge to vaccine makers.
At this point, we need to accept that we do not know the ending of the story. We have to use our experience and observation to relentlessly chase this moving target. Trying to stay two steps ahead is definitely the way to go.
Further reading
1. Not all antibodies are protective. Neutralizing antibodies are required.
2. The story of epidemics and pandemics
3. Vaccines, 6th edition, Stanley A. Plotkin, Walter Orenstein, Paul A. Offit
4. Long-term projections on COVID-19 based on mathematical models
5. Herd immunity and herd effect
6. Healthcare workers self-isolate to reduce risk to their family
7. Aerosol is the likely mechanism of super-spreading events
8. Interview with Dr Jayaprakash Muliyil, epidemiologist
9. COVID-19 related deaths in nursing homes in the US
10. COVID-19 related deaths in nursing homes in Toronto, Canada
11. List of vulnerable people, CDC
12. Underreporting of cases of COVID-19, world
