Getting Technical
CHARLES NICOLSON
Charles Nicolson has a physics and chemistry degree from Natal University which he subsequently put to good use by applying speciality chemicals in mining and industrial processes where water is a major factor . This created an enduring interest in water technology , a passion that expanded to the HVAC industry in 1984 when he joined BHT Water Treatment . Since then , water technology in HVAC water circuits has continued to be an abiding interest .
HERD IMMUNITY
By Charles Nicolson
A collective defence against the Covid-19 virus .
Now that effective vaccines are available to counter the current variants of the Covid-19 virus , the war against the dangerous disease caused by this virus is going to be won , although it will probably need additional time if viral mutations continue to produce new variants .
The actual time since the outbreak became apparent is surprisingly short . It has taken ( at the time of writing ) only 14 months to go into history as one of the worst – perhaps the worst pandemic ever – to occur .
When this highly infectious coronavirus first started to spread , virtually nobody was immune . Consequently , the virus spread rapidly across communities . In May 2020 , ten months ago ( at the time of writing again ), the city of Manaus in Brazil experienced a sudden , large outbreak of Covid-19 .
However , after three months the situation had changed . By August 2020 , despite having reduced social-distancing which had been introduced at the beginning of June 2020 , the number of deaths per day in this city of some 2-million people had reduced from over a hundred to less than ten .
Researchers suggested that one of the main reasons was because a large proportion of the community ’ s population had probably
experienced early individual exposure to the virus which enabled them to develop immunity .
Immunologist Ester Sabino at the University of São Paulo , Brazil , reported test results for antibodies to SARS-COV-2 ( the virus that causes Covid-19 ) on 6 000 samples from blood banks in Manaus showing that the number of infections resulting from the first wave reached nearly 70 %. Sabino proposed that this high infection rate meant that the number of people who remained vulnerable to the virus reduced rapidly to a level too small to sustain any new outbreaks ; a situation known as ‘ herd immunity ’, a term used in previous viral outbreaks for example of measles , mumps , or going back to the massive flu pandemic in 1918 .
Clearly , achieving herd immunity against any hostile virus is a desirable objective and many methods of achieving this have been proposed . Initially , a basic theme to simply leave the coronavirus to run its course was suggested allowing people to return to their
Michael Dantas / AFP via Getty
normal daily living while precautions were implemented to protect those at higher risk levels .
However , specialist epidemiologists were vigorously opposed to this approach insisting that it would undoubtedly result in needless loss of life . Kristian Andersen , an immunologist at the Scripps Research Institute in La Jolla , California , has stated that . “ Surrendering to the virus is not a defensible plan , we have never managed to do this successfully before for maladies such as mumps and polio and it will lead to unacceptable and unnecessary deaths and suffering without speeding up the return of society to normal ”.
Once a sufficient proportion of the population is no longer susceptible to the virus , any new outbreak diminishes and then peters out . “ You don ’ t need everyone in the population to be immune – you just need enough people to be immune ,” says Caroline Buckee , an epidemiologist at Harvard T . H . Chan School of Public Health in Boston , Massachusetts .
Many medical professionals do not like the term ‘ herd immunity ’ and prefer to call it ‘ herd protection ’. Buckee goes on to say that " The phenomenon doesn ’ t actually
Continued on page 45
A section of the cemetery in Manaus , Brazil , in June 2020 .
www . hvacronline . co . za RACA Journal I June 2021 43