Invasive, alien, most fearsome 

#GS3 #Pandemic #Health 

With so little known about its origin and pathogen emission rate, SARS-CoV-2 is the greatest challenge to mankind 

Invasive alien species are species of plants, animals and microbes which move out of their native location into alien locations and cause economic, ecological and health damage. 

Features of an alien invasive species 

  • All invasive alien species remain unproblematic in their land of origin where natural enemies limit their population increase.  
  • But when a species arrives at a new location, it escapes from the control of its natural enemies and its population explodes. 
  • In the case of SARS-CoV-2, the individual body of each and every host is a landscape in itself. Unlike in the case of SARS, where the virus jumped from bats to civet cats to humans, the intermediate host for SARS-CoV-2 remains unknown. 
  • The host is devoid of immunity against the pathogen. With no prior exposure to it and no antibodies, the body initiates a violent response against the new intruder, which could prove fatal. 
  • The idea of imposing lockdowns originated from this logic of slowing the spread. Unlike plants and animals which can be visually encountered, we need to contact-trace and test people to find out the extent of spread of this pathogen. 
  • This spread is a function of the reproductive rate of the virus (R0), which is defined as the number of cases, on average, an infected person will cause during the infectious period. 
  • R0 is a critical value in the case of all invasive alien species. If it is less than 1, the disease will vanish without causing an epidemic.  
  • As it goes above 1, the probability of an epidemic increases. In the absence of precise data for computing the R0 of SARS-CoV-2, the estimated value is somewhere between 1.5 and 3.5 and is zeroing in on 2.2. 
  • The SARS-CoV-2 outbreak has brought the global economy to its knees. The virus has infected 1.9 million, killed more than a lakh and put a huge strain on health systems.  
  • But its impact on the ecology is positive. Carbon emissions have decreased, and nitrogen dioxide emissions in northern Italy, Spain and the U.K. have faded. The sustainability of improved air quality will be seen soon. 

The question of herd immunity 

  • Since we don’t have a vaccine yet, the only other way to build immunity is to do so naturally, which is happening in the recovered cases. 
  • We will know only when the lockdown is lifted whether keeping the R0 value well below 1 for a reasonable period of time will really help us.  
  • The length of the period during which infected ones, with and without symptoms, spread the disease will decide how best we move out of the pandemic and how much time nature will get to repair itself. 
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