· 5 മിനിറ്റ് വായന

Covid and airborne transmission: the truth

Current Affairsകോവിഡ്-19പകര്‍ച്ചവ്യാധികള്‍പൊതുജനാരോഗ്യം

❓️Question: Is Coronavirus airborne, and can the disease be transmitted over air?

☑️Short Answer: No.

❓️Question: Didn’t the World Health Organization (WHO) issue such a public warning?

☑️Short Answer: NO, They did not.

❓️Question: If so, Why are many people, including doctors, claiming otherwise? Even big media portals such as CNBC carry news articles of such a possibility.

☑️Long Answer: This is an excellent example of how inaccurate scientific reporting can spread rumors and panic. It is also disheartening to see that many people, including medical professionals, are circulating these half-baked stories without reading beyond the headlines or dwelling into the source study.
Let us look at this manipulated claim of airborne transmission in detail.

The CNBC article was based on a “guideline of precaution” issued by WHO specifically to medical staff, but not to the general public. Medical professional have a high risk to be exposed to “aerosols” generated from various medical procedures that they perform on Covid-19 patients. WHO insisted that in order to protect themselves from a possible infection via these aerosols medical professionals should take “airborne precautions” while treating Covid-19 cases.

These precautions include wearing N95 masks and special biosafety suits. The WHO spokesperson also clarified beyond any reasonable doubt that this is not a common transmission method of the virus and such extreme precautions are not meant for the general public. (Please find the video in the comments).

For all those curious minds out there, let’s dwell deep.

Even Longer Answer: There is a common misconception that all illnesses of the lungs and respiratory system are airborne, (and why think otherwise, isn’t it air what fills our lungs?)
This is not true. Most of the respiratory communicable diseases are not airborne but are transmitted through droplet infection. The difference between airborne and droplet infections is simple. In the former, the pathogenic organism (virus or bacteria) can transmit from one person to another through air, and in the latter, the pathogen is carried by droplets generated by the respiratory secretions of the patients.

The airborne pathogens not only suspend in the air but most often can travel long distances. A good example is Varicella Zoster, the causative agent of chickenpox. This virus can transmit the disease by traveling up to 9 kilometers away from the source .Additionally, these viruses stay floating in the air even after the patient has left.
On the other hand, droplet infections are more forgiving. These pathogens neither stay suspended in air, nor can they travel long distances. They are buried inside respiratory droplets (very small water drops generated while we speak, exhale, cough, sneeze etc). These droplets are heavy compared to individual viruses and will settle on surrounding surfaces soon as they are formed.
Covid-19 and all other coronaviruses are transmitted this way, and that is why covering your face, washing your hands after touching objects and maintaining a social distance of 1 meter helps to prevent the spread of this disease.

However, certain medical procedures such as nebulization, intubation post-mortem examination and aspirating respiratory fluids can generate absolutely fine droplets which can stay afloat in the air for a longer duration than normal. These droplets are called “aerosols”. When such procedures are performed on Covid-19 patients, the resulting aerosols can potentially infect anyone in the vicinity. Even then, these aerosols will not travel for long duration and distance through the air as an airborne pathogen. Not just Covid-19, but other coronaviruses including SARS also exhibit such an “opportunistic” behaviour.

This is why WHO is insisting on airborne precautions to all medical staff treating Covid-19 infected persons, and such the general public need not observe such precautions because aerosols are not a common occurrence outside hospital settings.

Covid-19, though its called “novel”, shares similar morphology and characteristics as other coronaviruses, and have a slightly modified genetic composition. Hence without substantial changes in its morphology and physical composition from other coronaviruses, it cannot transform into an airborne pathogen. Unlike genetic modifications, this kind of transformations are hard to come by.

Nevertheless, there is one published report of a probable aerosol formation in non-hospital conditions. It was suspected that the pressure variation caused by an exhaust fan in an unused vent pipe of a multistory building lead to the generation of SARS containing aerosols and subsequent infections. As you might have guessed these circumstances are highly unlikely to happen. Normal activities, such as speaking, coughing etc will not result in the generation of corona virus containing aerosols.

Does it mean that the study reported by CNBC was substandard?

The study reported in CNBC also concludes that Covid -19 is not airborne in normal circumstances. It is the substandard reporting and click-bait title which caused all the havoc.

Authors of the aforementioned study found out that the aerosols of Covid-19 can be found up to 3 hours after its generation. But they could not estimate the virus load in aerosols required for infection.

The study was uploaded on to a pre-database – medRxiv on March 10th and was later updated on March 13, 2020. But these reports are preliminary since they are not subjected to a wide peer review yet, and therefore, the results are not exactly solid.

According to the co-author Dylan Morris, a graduate student in the Department of Ecology and Evolutionary Biology at Princeton University, they still don’t know the minimal concentration of viable SARS-CoV-2 needed to practically infect a human being, though this is something they are looking to model in the future. Also, the aerosol infection, though theoretically possible, won’t be a driving force behind this pandemic; Morris added.

Twisting these inconclusive and mostly boring scientific reports to a ‘shocking’ heading could get them more views, but spreading half-truths and panic-inducing click baits should be considered an offence.

According to WHO, “infodemic” or the abundance of unverified information is as dangerous as the pandemic itself.

ലേഖകർ
Dr. Deepu Sadasivan. Obtained a medical degree from Kottayam Medical College. Currently working in Kerala State health services department. Articles related to Medical science have been published in periodicals and newspapers.
ചിത്രകാരൻ
Design Co-ordinator, Infoclinic.

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