Business Day

Ven­ti­lat­ing the study of a stub­born epi­demic

- TAMAR KAHN kahnt@bdlive.co.za

AS A school­boy in Birm­ing­ham, Robin Wood was once given the task of open­ing and clos­ing the high win­dows in his class­room us­ing a long pole. Good ven­ti­la­tion was con­sid­ered key to sound health and a sharp mind.

Wood is now a lead­ing sci­en­tist at the Univer­sity of Cape Town, puz­zling over why the city has such a rag­ing tu­ber­cu­lo­sis (TB) epi­demic. He spends much of his time hunt­ing for clues on how the dis­ease is spread, and how it has been in the past.

Un­like Eu­ro­pean cities that ex­ported TB to SA along with their colo­nial-era im­mi­grants in the 19th cen­tury, Cape Town has never man­aged to get the dis­ease un­der con­trol. There were al­most 30,000 newly no­ti­fied cases of TB in 2009 among the city’s 3.4-mil­lion in­hab­i­tants, ac­cord­ing to a study pub­lished in the sci­en­tific journal PLOS ONE. The in­ci­dence of TB in Cape Town was 479 per 100,000 of the pop­u­la­tion in 2014, ac­cord­ing to the Western Cape health depart­ment.

By con­trast, the in­ci­dence in New York was just 7.7 cases per 100,000 in 2015.

“Cape Town alone has more TB each year than the US, Canada, UK and Ger­many put to­gether. The ques­tion is why,” says Wood, co-di­rec­tor of the Des­mond Tutu HIV Cen­tre and a re­searcher at UCT’s In­sti­tute of In­fec­tious Dis­ease and Molec­u­lar Medicine.

Wood and his col­leagues have turned to records col­lected by health au­thor­i­ties over more than a cen­tury in three cities hard hit by TB in the early 1900’s — New York, Lon­don and Cape Town.

They plot­ted TB no­ti­fi­ca­tion rates be­tween 1910 and 2012 and no­ticed some­thing star­tling. Even be­fore the ad­vent of the first an­tibi­otic treat­ment in the late 1940’s, the rate was plum­met­ing in New York and Lon­don and con­tin­ued to fall steadily over the course of the cen­tury.

Yet in Cape Town it re­mained stub­bornly high and to­day re­mains at lev­els last seen in in­dus­tri­al­is­ing Europe in the 19th cen­tury. The TB no­ti­fi­ca­tion rate hov­ered at about 450 cases per 100,000 be­tween 1910 and 1945, fell briefly af­ter the in­tro­duc­tion of an­tibi­otic ther­apy to a low of 250 cases per 100,000 in 1970, but rose again to 450 per 100,000 in 1995 and soared with the HIV/AIDS epi­demic to 850 per 100,000 in 2010.

Many healthy peo­ple get in­fected with TB but never de­velop the dis­ease, but the HIV weak­ens the im­mune sys­tem and makes peo­ple more sus­cep­ti­ble to it. Yet even among HIV-neg­a­tive peo­ple, the TB no­ti­fi­ca­tion rate in Cape Town be­tween 2009 and 2012 was breath­tak­ingly high: 445 per 100,000 pop­u­la­tion. (It was 6,338 per 100,000 among those who were HIV-pos­i­tive). A sim­i­lar pat­tern was ob­served for TB mor­tal­ity rates.

The pe­riod be­tween 1950 and 1960 in Cape Town of­fers a clue as to why the dis­ease re­mains rife, says Wood, as this was the only time when a sig­nif­i­cant fall in TB mor­tal­ity was recorded. Dur­ing this era the city em­barked on a process known as “ac­tive case find­ing” in which it screened masses of peo­ple for TB rather than wait­ing for sick peo­ple to care. TB mor­tal­ity de­clined by 60%.

“It’s a bit of cir­cum­stan­tial ev­i­dence sug­gest­ing that maybe we need to think again,” says Wood.

The scale of Cape Town’s TB prob­lem means there are large num­bers of in­fected peo­ple spread­ing the dis­ease for months be­fore they are di­ag­nosed and start treat­ment. Break­ing the back of the epi­demic will re­quire break­ing this trans­mis­sion cy­cle, says Wood.

“In places like the Cape Flats and the town­ships, peo­ple get in­fected mul­ti­ple times,” he says.

Peo­ple liv­ing in these com­mu­ni­ties in­habit a ver­i­ta­ble soup of TB, be­cause they are ex­posed to hun­dreds of dif­fer­ent strains of the dis­ease.

SA’s TB con­trol poli­cies are aligned with the World Health Or­gan­i­sa­tion’s and fo­cus on di­ag­nos­ing and treat­ing pa­tients who seek med­i­cal at­ten­tion, rather than ac­tively look­ing for cases. Wood says this pol­icy is based on ev­i­dence from the West’s ex­pe­ri­ence with TB and sug­gests the pro­gramme needs to be adapted to dif­fer­ent cir­cum­stances.

“If you are in a Pollsmoor Prison cell for 23 hours a day, with no ven­ti­la­tion and over­crowd­ing at 300%, the TB con­trol pro­gramme can­not be the same as out­side or you won’t touch the epi­demic. We can’t treat our way out of it,” Wood says.

Wood has also been study­ing the risk of TB trans­mis­sion among high school chil­dren from Masi­phumelele town­ship, by kit­ting them out with car­bon diox­ide mon­i­tors and track­ing their move­ments.

Car­bon diox­ide is a proxy mea­sure for shared air, and en­abled the re­searchers to es­ti­mate where the stu­dents were at high­est risk of catch­ing TB. They found the pupils spent 60% of their time in rooms where the car­bon diox­ide level was above a safe thresh­old, the worst of which were poorly ven­ti­lated class­rooms.

This kind of work has made him a keen ad­vo­cate for well ven­ti­lated class­rooms, as bet­ter air flow would re­duce pupils’ risk of catch­ing TB. Like pris­on­ers, they are com­pelled to spend much of their time in a con­fined and crowded space.

The least the ed­u­ca­tion sys­tem can do is make sure their schools don’t make them sick, he says.

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