Lessons learned

Fighting Blind

Professor David Heymann, advisor to the WHO on Covid-19, says there are many unknowns about the disease, but valuable lessons too.

Soeren Kunz/Wildfoxrunning

The one con­stant that has char­ac­ter­ized Covid-19 is uncer­tain­ty. With some big epi­demi­o­log­i­cal ques­tions unan­swered, we are strug­gling to pre­dict the des­tiny of the virus. Will Covid-19 dis­ap­pear as fast as it arrived, or will it become endem­ic, like sea­son­al influen­za? Will catch­ing it pro­vide immu­ni­ty or will it, like the dengue fever virus­es, be more severe the sec­ond time around? With­out a sen­si­tive anti­body test, we can­not be cer­tain about com­mu­ni­ty spread. We also do not ful­ly under­stand the clin­i­cal spec­trum. With 80 per­cent of symp­toms being mild and around 9 per­cent of cas­es show­ing no symp­toms, we do not know why some oth­er­wise healthy peo­ple suc­cumb, and some with under­ly­ing health con­di­tions get away with mild symp­toms.


Professor David Heymann

is Professor of Infectious Disease Epidemiology at London School of Hygiene and Tropical Medicine. Previously he was WHO Executive Director of the Communicable Diseases Cluster, a position from which he headed the global response to SARS.

For Pro­fes­sor David Hey­mann, a vet­er­an of dis­ease out­breaks, the gaps in our knowl­edge are trou­bling. He is cur­rent­ly chair of the inde­pen­dent advi­so­ry group to the WHO on Covid-19 and led the glob­al response to SARS in 2003. Some of the deci­sions tak­en by gov­ern­ments to pro­tect their cit­i­zens wor­ry him. His biggest sur­prise is the speed and sever­i­ty with which soci­etal lock­downs came into force “With no cer­tain­ty about a vac­cine it is wrong for coun­tries that have locked down to say that they will now keep the repro­duc­tive lev­el low until there is a vac­cine, it is the wrong hypoth­e­sis. The way for­ward is to do every­thing you can to keep the virus at a lev­el you feel your coun­try can sus­tain.” The big unknown is whether we will come up with an effec­tive vac­cine. Hey­mann believes there is no guar­an­tee we will.

“My fear is that many coun­tries have entered these lock­downs with­out a clear exit strat­e­gy,” he says. He points to Swe­den, much maligned ini­tial­ly but now attract­ing grow­ing inter­est as an exam­ple of allow­ing the virus to enter in a con­trolled man­ner. Swe­den has imple­ment­ed rules around gath­er­ings and restau­rant seat­ing dis­tances, but has adopt­ed a bot­tom-up approach to con­tain­ment by trust­ing the pop­u­la­tion to act respon­si­bly. Asian coun­tries such as South Korea and Viet­nam have also suc­cess­ful­ly avoid­ed total soci­etal lock­downs while still man­ag­ing to stem trans­mis­sion. Hey­mann feels polit­i­cal deci­sions were dri­ven by an unfor­tu­nate sequence of events over the first three months of the out­break.

My fear is that many countries have entered these lockdowns without a clear exit strategy

Professor David Heymann
Professor of Infectious Disease Epidemiology at London School of Hygiene and Tropical Medicine

The Chi­nese lock­down of Wuhan appeared to be work­ing at the time that Italy’s health­care sys­tem became rav­aged by the virus. Oth­er gov­ern­ments did not want to take the risk of let­ting that hap­pen to their coun­tries and want­ed to be seen to take firm action. What remained unclear as the lock­downs were intro­duced was the impact on social inequal­i­ty. “Espe­cial­ly those who live hand to mouth and then lose their day-to-day employ­ment. In many instances they are also the ones with comor­bidi­ties which I find extreme­ly con­cern­ing as an epi­demi­ol­o­gist,” he says.

100 % of those infected

with Covid-19 have shown no symptoms at all, with 80% of symptoms being mild (as of May 19, 2020).


Anoth­er unknown about Covid-19 is why it ini­tial­ly appears to be dis­pro­por­tion­ate­ly affect­ing the devel­oped world. There are a num­ber of the­o­ries in play around trav­el inter­con­nec­tiv­i­ty, the low aver­age age of those in devel­op­ing coun­tries, and that it may be too ear­ly to tell what the full impact will be. “It is pos­si­ble all these are work­ing togeth­er, and we will see dif­fer­ent epi­demi­ol­o­gy in dif­fer­ent parts of the world,” says Hey­mann. While there is a lot to be con­cerned about with Covid-19, one of the most encour­ag­ing respons­es has been the lev­el of glob­al tech­ni­cal coop­er­a­tion, which belies some of the geopo­lit­i­cal ten­sions at the top lev­els of gov­ern­ment. Hey­mann points to coop­er­a­tion between the Chi­nese and Amer­i­can cen­ters of com­mu­ni­ca­ble dis­ease. “As chair of the inde­pen­dent advi­so­ry group to the WHO pro­gram, I have access to all this infor­ma­tion and it real­ly is quite amaz­ing how freely data is being shared,” he says. He also rec­og­nizes the way sci­en­tif­ic jour­nals are allow­ing open source access and the speed at which research is being peer reviewed as a crit­i­cal tool in try­ing to con­tain the virus.

In my role for the WHO, I have access to all of this information, and it really is quite amazing how freely data is being shared.

Professor David Heymann
Professor of Infectious Disease Epidemiology at London School of Hygiene and Tropical Medicine

In mid-May, as many coun­tries in the West were try­ing dif­fer­ent meth­ods to release cit­i­zens from lock­down, Asia start­ed to go in the oppo­site direc­tion. “They are intro­duc­ing what you could call cir­cuit break­ers, where they intro­duce a lock­down for a few weeks or months and then remove it. An exam­ple is Hong Kong, which shut down its nightlife for a cou­ple of weeks,” says Hey­mann. As the pan­dem­ic devel­ops, unan­swered ques­tions will be resolved and, with the com­fort of time, we will be bet­ter able to assess which epi­demi­o­log­i­cal approach is best suit­ed to which cir­cum­stances. One of the bit­ter­sweet ben­e­fits of a glob­al pan­dem­ic is that, ulti­mate­ly, it will pro­vide many dif­fer­ent mod­els from which to learn how to com­bat future dis­eases.

1 Immediately develop a full strategy to include societal lockdown measures through to relaxing restrictions. 2 Trust the epidemiological evidence to ensure you protect all citizens, including the most vulnerable. 3 Global cooperation and shared knowledge are inevitable in the face of disease threat. A global crisis can only be solved together.
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