Integration between science and policy crucial to prevent public health pandemic
As of June 16, Covid-19 has infected over 8141805 people worldwide and caused 439748 fatalities across the globe. The pandemic has compelled countries to resort to extreme measures to prevent the spread of the virus and protect their people, yet many measures have failed.
Recent research published by the University of Texas in collaboration with the University of California and Robert A Welch Foundation reveals that using masks in public is the single most effective means to prevent the inter-human transmission of Coronavirus. Social distancing and quarantine certainly reinforce these steps. The study analyzed the trends and mitigation measures in Wuhan, Italy, and New York City, from January 23 to May 9, 2020. The findings reveal that masks alone significantly reduced the number of infections by over 78,000 in Italy from April 6 to May 9 and over 66,000 in New York City from April 17 to May 9, 2020.
The Covid-19 infection continues to spread at an alarming rate across the world. The magnitude of the challenge posed by coronavirus reflects its highly contagious nature. Analyzing the trend of Covid-19 from January 23 to May 9, 2020, the study suggests airborne transmission of the virus via aerosols as the potential route for the spread of disease.
The coronavirus contains a single-stranded RNA genome and a nucleocapsid of helical symmetry of ∼120 nm. The virus is transmitted in a number of ways. The virus-bearing particles occur from coughing/sneezing and even from normal breathing/talking by an infected person. These mechanisms produce large droplets and small aerosols, which are 5 μm in size. Virus transmission occurs in three different ways –
- Direct – Deposited on persons
- Indirect – Deposited on objects or contact and
- Airborne – Droplets and aerosols routes.
Large droplets readily settle out of the air to contaminate a person or object; in contrast, aerosols spread in the air. While transmission via direct or indirect contact occurs in a short-range; airborne communication via aerosols can occur over an extended distance and time. When a person inhales virus-bearing aerosols, it is deposited directly along the human respiratory tract.
Previous studies on interhuman transmission have indicated a significant role of aerosols in the transfer of many respiratory viruses, including influenza virus, SARS-CoV-1, and the Middle East Respiratory Syndrome coronavirus (MERS-CoV).
Airborne coronavirus (MERS-CoV) exhibited strong capability of surviving, with about 64% of microorganisms remaining infectious 60 min after atomization at 25 degrees C and 79% relative humidity. On the other hand, rapid virus decay occurred, with only 5% survival over a 60-min procedure at 38 degrees C and 24% relative humidity, indicative of inactivation.
Recent experimental studies have examined the stability of SARS-CoV-2, showing that the virus remains infectious in aerosols for hours and on surfaces up to days.
Survival of virus depends on several variables like temperature, humidity, resistance to physical and biological stresses, and ultraviolet radiation. During typical nasal breathing, airborne viruses get deposited in the respiratory tract of humans. Fine aerosols even reach vital organs after penetrating deep into the respiratory tracts. The release of the virus is dependent on the stage of infection and varies between asymptomatic and symptomatic carriers. It poses a grave threat to the elderly, children, and people with low immune. The highest viral load in the respiratory tract occurs during the onset of infection and this is the leading cause of mortality and morbidity worldwide. The study highlights the outbreak of the diseases in Wuhan, China which was the epicenter of the epidemic in early 2020. The epicenter shifted to Italy in early March and to New York City in early April. The numbers in the United States continue to increase even today. As the curve flattened in China, it increased in other countries. The decline in cases
can be attributed to aggressive measures like extensive testing, contact tracing, quarantine, the mandatory wearing of masks, including complete lockdown of all cities in the country. Although Italy took similar measures, it did not decrease the rate of infection. In the US, guidelines for social distancing, quarantine, no gatherings in groups were implemented only in Mid-March. The continuous rise in the number of cases in the United States casts doubt in the effectiveness of these measures.
Apart from China, western countries did not make wearing masks mandatory. Advice on covering the face was not made by The World Health Organisation until April 6, claiming that it is essential only to prevent infected persons from transmitting the virus by filtering out droplets but that it is not essential to prevent uninfected persons from breathing virus-bearing aerosols. Lombard, the region that was heavily plagued by COVID-19 ordered face-covering in public starting April 6, and the Italian Government made nationwide mandatory use of face masks on May 4. When mass distancing was not possible in New York, people were asked to cover face starting April 17. The measures in the United States did little to stop the spread of the disease.
The study further adds that physical separation for social distancing is beneficial to prevent direct contact transmission but is insufficient (without face masks) to protect the inhalation of virus bearing aerosols. The study especially quantified the effects of face-covering by projecting the number of infections based on the data before implementing the use of face masks in Italy on April 6 and New York City on April 17. The study found that face-covering reduced the number of infections by over 78,000 in Italy from April 6 to May 9 and by over 66,000 in New York City from April 17 to May 9. It also shows the inability of other measures like social distancing, quarantine, and isolation alone in curbing the spread of COVID-19. Face covering significantly shaped trends worldwide.
The research also compared the spread between New York City and the United States from March 1 to May 9. The numbers showed a sharp increase in late March and early April. After April 3, the only difference in the regulatory measures between New York and the United States lies in face-covering that was mandatory in NYC on April 17. The decreasing rate in the daily new infections in New York with mandated face-covering is in sharp contrast to that in the United States with only social-distancing and stay-at-home measures. This further confirms the importance of face-covering in preventing virus transmission.
Face covering prevents both airborne transmission and contact transmission. On the other hand, social distancing, quarantine, and isolation, in conjunction with hand sanitizing, minimize contact (direct and indirect) transmission but do not protect against airborne transmission. With social distancing, quarantine, and isolation in place worldwide and in the United States since the beginning of April, airborne transmission represents the only possible route for spreading the disease, when mandated face covering is not implemented. Face covering blocks atomization and inhalation of virus-bearing aerosols which significantly reduced infections in China, Italy, and New York, indicating that airborne transmission of COVID-19 represents the dominant route for infection.
The research also examined the weather condition during outbreaks in China, Italy and the US. The initial outbreak of COVID-19 in Wuhan coincided with the winter mist season in China during which period the PM2 levels were high. However, in Italy and the US, the PM2 levels were lower during the disease outbreak. Virus-bearing aerosols produced from human atomization transform in air, including thickening with pre-existing ambient PM within few hours in typical urban air.
Even with normal nasal breathing, inhalation of the virus bearing aerosols results in deep and continuous deposition into the human respiratory tract. Residents situated in densely populated environments are highly vulnerable. Besides, aerosols produced from coughing/sneezing have the potential of containing many viruses, particularly for asymptomatic carriers.
The Governments response to Covid-19 has differed across the world. China took prompt action and implemented various mitigating measures timely. However, the response was delayed and slow in many western countries. The response and the mitigation measures governed the magnitude of the pandemic globally.
In the US, during the early stages of the pandemic, social distancing, stay-at-home measures, and hand sanitizing minimized the short-range contact transmission but did not prevent long-range airborne transmission. Mandated face-covering in China, Italy, and the US effectively prevented airborne transmission.
While social distancing and face-covering offer double protection, the timing of implementation of these measures also result in different outcomes. For example, in Italy and New York City, social distancing and stay at home orders were implemented before the face-covering directive was put in place, and this resulted in uninterrupted airborne transmission. The simultaneous implementation of social distancing and face covering in China was most effective and resulted in reducing the number of cases. Not recognizing the consequence of airborne transmission of the virus was the biggest failure in containing the spread of the infection.
To conclude, the research adds that governments have not considered the importance of airborne transmission as an established mitigation measure. Both the World Health Organization and the Centre for Diseases Control and Prevention have ignored the importance of airborne transmission routes. Social distancing, isolation, and quarantine are ineffective in protecting the public. Face covering is the most effective means to prevent inter-human transmission. Implementing policies without a scientific basis could lead to catastrophic consequences, particularly in the light of attempts to reopen the economy in many countries.
Integration between science and policy is crucial to the formulation of effective emergency responses by policymakers and preparedness by the public for the current and future public health pandemics. The single most effective measure of face covering, if implemented timely across the world could have saved millions of lives.