38 Scientific American, October 2020Like all viruses, coronaviruses are expert code crack-
ers. SARS-CoV-2 has certainly cracked ours. Think of this
virus as an intelligent biological machine continuously
running DNA experiments to adapt to the ecological niche
it inhabits. This virus has caused a pandemic in large part
because it acted on three of our most human vulnera-
bilities: our biological defenses, our clustering patterns
of social behavior and our simmering political divides.
How will the confrontation unfold in the next years
and decades? What will be the human toll in deaths,
ongoing disease, injuries and other impairments? How
effective will new vaccines and treatments be in con -
taining or even eradicating the virus?
No one can say. But several lessons from the long
battle with HIV, the human immunodeficiency virus
that causes AIDS, suggest what may lie ahead. HIV/
AIDS is one of the worst scourges humans have encoun-
tered. As a code cracker, HIV is an expert. By the end of
2019 the global death toll from this virus was roughly
33 million people. In all, 76 million people have been
infected, and scientists estimate another 1.7 million
people acquire the virus every year.
Yet we must appreciate what our scientific defenses
have accomplished. Of the nearly 38 million people cur -
rently living with HIV/AIDS, 25 million are receiving full
antiretroviral treatments that prevent disease and sup -
press the virus so well they are unlikely to pass it along.
I would wager that another 25 million or more infections
never happened, primarily in sub-Saharan Africa, because
these treatments became available in most countries.
From fighting this epic war against AIDS, doctors,
virologists, epidemiologists and public health experts
have learned crucial lessons that we can apply to thebattle we are currently waging. For instance, we saw
that vaccines are never a guarantee but that treatments
can be our most important weapon. We discovered that
human behavior plays a vital role in any disease-fight-
ing effort and that we cannot overlook human nature.
We have also seen how critical it is to build on knowl-
edge and tools gained fighting earlier outbreaks—a
strategy only possible if we continue funding research
in between pandemics.VACCINE CHALLENGES
Early obsErvations of how HIV behaves in our bodies
showed the road to a vaccine would be long and challeng-
ing. As the outbreak unfolded, we began tracking anti-
body levels and T cells (the white blood cells that wage
war against invaders) in those infected. The high levels
of both showed that patients were mounting incredibly
active immune responses, more forceful than anything
we had seen for any other disease. But even working at
its highest capacity, the body’s immune system was nev-
er strong enough to clear out the virus completely.
Unlike the hit-and-run polio virus, which evokes
long-term immunity after an infection, HIV is a “catch
it and keep it” virus—if you are infected, the pathogen
stays in your body until it destroys the immune system,
leaving you undefended against even mild infections.
Moreover, HIV continually evolves—a shrewd opponent
seeking ways to elude our immune responses. Although
this does not mean a vaccine is impossible, it certainly
meant developing one, especially when the virus hit in
the 1980s, would not be easy. “Unfortunately, no one
can predict with certainty that an AIDS vaccine can ever
be made,” I testified in 1988 to the Presidential Commis-“
W
E arE now EngagEd in anothEr dEadly EpisodE in thE historic
battle of man versus microbe. These battles have shaped the
course of human evolution and of history. We have seen the
face of our adversary, in this case a tiny virus.” I spoke these
words in testi mony before a U.S. Senate subcommittee on
September 26, 1985. I was talking about HIV, but I could say
the same thing today about the coronavirus we are facing.William A. Haseltine is a former Harvard Medical School professor and
founder of the university’s cancer and HIV/AIDS research departments.
He also serves as chair and president of the global health think tank ACCESS
Health International. He has founded more than a dozen biotechnology
companies and is the author, most recently, of A COVID Back to School Guide:
Questions and Answers for Parents and Students and A Family Guide to
COVID-19: Questions and Answers for Parents, Grandparents and Children.© 2020 Scientific American