Lock down not the correct method: 9.6% trapped on the ship acquire COVID-19

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17th Feb: 70 new cases on board the cruise ship in Japan. Nearly 1 out of 10 passengers and crew (9.6%) have tested positive for the virus so far (355 cases out of 3,711 passengers and crew). The 952-foot cruise ship carries the highest infection rate of the coronavirus anywhere in the world.

China has imposed quarantines across Hubei province, locking down over 56 million people, in order to stop COVID-19 from spreading.

Villages in Vietnam with 10,000 people, close to the nations capital, have also been placed under quarantine after six cases of the new coronavirus were identified there. The locking down of the commune of Son Loi, about 40 kilometres from Hanoi, is the first mass quarantine outside of China since the virus emerged from central China late last year.

If you lock down COVID-19 infected people with non-infected people, the transmission will be around 10%. This will still be insufficient to start the herd immunity chain. The idea of lock down probably was to develop herd immunity in the locked down population but with R0 value of 3, it looks impossible.

Over the last four days, the number of new cases in China has been declining.

Limitations of quarantine

  1. The people on lockdown are kept under a 14-day quarantine. If they are placed together and if anyone is diagnosed with the infection during that period, the quarantine will add another 14 days.
  2. In China, the lock down has not been lifted so far.
  3. The longer several thousand people are cohoused, it goes on to propagate waves of infection.
  4. A better way is to divide the people into smaller groups and quarantine them separately.
  5. Why quarantine children <15 years of age when the virus is not risky for them.
  6. Why not separate elderly people with comorbid conditions at high risk of death and quarantine them separately in one-to-one or small groups.
  7. Ventilation system can connect one room to the other. There has been concern that the coronavirus can spread through pipes.
  8. Stress and anxiety suppress the immune system, thus rendering people more vulnerable to contracting the virus.
  9. Why not quarantine them in open sunlight.

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA

Basic reproduction number, or R0 or contagiousness

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R0 represents the average number of susceptible individuals an infected person will transmit the disease to.

R0 = Attack rate x Contacts

Attack rate (the percent chance that a contact will get the disease).

If the R0 is < 1, a disease outbreak should wane over time, and if its >1, cases would continue to increase.

Seasonal flu has an R0 of around 1.5. The Spanish influenza of 1918-1919 had an R0 of 2. Chickenpox, a fairly infectious condition, has an R0 of around 5.

To predict the severity of a new disease, we need to look at both the basic reproduction number and the case fatality rate.

The case fatality rate of Spanish flu was reported to be as high as 10%.

Before treatment was available, HIV, with an R0 of around 6 globally, had a near 100% mortality rate. Smallpox, with an R0 of 5, had a mortality rate of 30% in the unvaccinated. Bubonic plague: R0 of 3, untreated mortality rate of 60%.

COVID-19

COVID-19 has R0 of 2.5 and a reported case fatality rate of around 2%.

Case fatality rate is defined as the number of fatal cases divided by the number of total cases.

In COVID-19, fatal cases have probably been assessed accurately; people who are that sick generally end up in hospitals. However, the number of total cases are probably being missed by huge margins, perhaps even an order of magnitude, as asymptomatic and mildly symptomatic people may not be getting tested. If this is the case, the case fatality rate would decrease as screening improves.

How to change the R0 number

One can do that by addressing the two elements inside it: the number of contacts an infected person has and the attack rate of the disease.

Limiting potential contacts can be achieved by means of isolation and quarantine.

Attack rate can reduce with the use of masks, handwashing, and vaccination, as and when a vaccine becomes available.

This depends on identifying cases, and it is still unclear as to whether transmission can occur in the asymptomatic period. The latent period is 5 days.

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA

National Respiratory Infection Control Program

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Droplet precautions

Droplets are particles of respiratory secretions ≥5 microns that remain suspended in the air for limited periods. Exposure within three to six feet (one to two meters) of the source can transmit the infection.

Droplet precautions are essential while caring for patients with suspected or confirmed infections with Neisseria meningitidisBordetella pertussis, influenza, parainfluenza, adenovirus, Haemophilus influenzae type b, Mycoplasma pneumoniae, rubella, COVID-19.

  1. Respiratory viruses (such as parainfluenza virus and COVID-19) can be transmitted by contact and/or via droplets; both contact and droplet precautions should be implemented.
  2. Respiratory syncytial virus (RSV) may be transmitted through droplets but is primarily spread by direct contact with infectious respiratory secretions. Therefore, the most important intervention for prevention of RSV transmission in healthcare settings is adherence to contact precautions (plus standard precautions).
  3. The CDC does not recommend droplet precautions for RSV. However, droplet precautions are warranted if the infecting agent is not known, if the patient may be coinfected with other pathogens that require droplet precautions, and if exposure to aerosols of infectious respiratory secretions is probable.
  4. Healthcare workers caring for patients on droplet precautions should wear a surgical mask when they are within six feet of patients.
  5. No special air handling systems or higher-level respirator masks are required for the care of patients with known or suspected infection due to organisms capable of droplet transmission.
  6. The doors of rooms used to house these patients may remain open (in contrast with airborne precautions).

Contact precautions

Contact precautions are needed for patients with select multidrug-resistant bacteria and several enteric and viral pathogens.

Patients requiring contact precautions should be kept in a private room or in a cohort with other patients having the same indication for contact precautions.

Certain respiratory viruses (such as parainfluenza virus) can be transmitted by contact and/or through droplets. Both contact and droplet precautions are thus required for patients with known or suspected infection due to such organisms.

Healthcare workers must perform hand hygiene and wear gloves on entering the room, even if no direct patient contact is anticipated. Gowns are a must even if direct contact with the patient or infective material is not likely.

Upon room exit, gowns and gloves should be removed and hand hygiene should be performed immediately as hands become contaminated during glove removal.

Medical equipment should be used for a single patient only when possible in order to avoid transfer of pathogens by means of fomites. Equipment not dedicated to a single patient ought to be cleaned and disinfected prior to reuse.

Airborne precautions

Airborne droplet nuclei are particles of respiratory secretions <5 microns. Droplet nuclei can remain suspended in the air for extended period of time and thus can be a source of inhalational exposure for susceptible individuals.

Airborne precautions are warranted for the care of patients with suspected or confirmed tuberculosis, measles, varicella, smallpox, and severe acute respiratory syndrome (SARS).

Patients on airborne isolation precautions should be kept in a private room with negative air pressure with minimum  6 to 12 air changes per hour.

Doors to the isolation room must remain closed, and all individuals entering the room must wear a respirator with a filtering capacity of 95 percent that allows a tight seal over the nose and mouth.

In the setting of herpes zoster, airborne and contact precautions are warranted for all patients with disseminated zoster and for immunocompromised patients with localized zoster. Dtandard precautions may work for immunocompetent patients with localized zoster that can be contained/covered. Susceptible healthcare workers should refrain from providing direct care to these patients if immune caregivers are available.

COVID19 is transmitted predominantly by droplet spread and direct contact, although airborne transmission may also occur, especially during aerosol-generating procedures like endotracheal intubation; therefore, both airborne and contact precautions are warranted.

Patients in respiratory isolation who require transport outside their isolation rooms for medical procedures should wear surgical masks that cover the mouth and nose during transport. Procedures for these patients should be scheduled when they can be performed quickly and when occupation of waiting areas is minimal. [uptodate.com]

Dr KK Aggarwal

President CMAAO, HCFI and Past National President IMA

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