CAPE TOWN, SOUTH AFRICA—Living with HIV or active tuberculosis (TB) increases a person’s likelihood of dying from COVID-19, preliminary data from South Africa show. However, the effect is small compared with other known risk factors such as old age and diabetes.
South Africa has the world’s highest rates of HIV and TB infection. To gauge their impact on COVID-19, scientists in South Africa’s Western Cape province analyzed outcomes for 12,987 patients with the disease. After adjusting for other risk factors, they found HIV increased a COVID-19 patient’s death risk by a factor of 2.75, and active TB by a factor of 2.58. (The study did not yield data for people who have both HIV and TB.)
Those numbers pale in comparison with other known COVID-19 risk factors. In the same analysis, for example, people in their 50s were nearly 10 times more likely to die than those below age 40. And diabetics were between four and 13 times more likely to die than nondiabetics, depending on how well their blood sugar was controlled.
The findings suggest neither HIV nor TB should be considered “major” risk factors for COVID-19, says Mary-Ann Davies, a public health expert working for the Western Cape government, who presented the data in a public webinar on 9 June. “We don’t need to worry as much that we will see this overwhelming COVID-19 mortality for people living with HIV or TB,” Davies tells ScienceInsider. That’s a relief given that 7 million South Africans—about 12% of the population—are thought to live with HIV, and in 2018 more than 170 South Africans died from TB every day.
The study controlled for some known COVID-19 risk factors—including age and comorbidities such as high blood pressure—but not all. For example, the researchers could not rule out that HIV-infected people in the study were also more obese than the general population, which would put them at an increased risk as well. But Robert Wilkinson, an HIV and TB researcher who splits his time between here and London, believes that’s unlikely. “It could be that the vast majority of HIV infected people who are dying are also obese, but I’m skeptical about that,” he says.
How HIV and TB might interact with COVID-19 is poorly understood. HIV compromises the immune system, making carriers more susceptible to TB and, possibly, COVID-19. And TB can damage the lungs, perhaps leaving people more susceptible to severe COVID-19. But most studies to date have been too small to be conclusive. In March, Chinese scientists published a preprint suggesting TB increases susceptibility for severe COVID-19. However, critics said the sample size was too small to be reliable. A paper published in Clinical Infectious Diseases on 14 May that looked at 47 HIV-positive patients hospitalized with COVID-19 in Italy found HIV was not a risk factor for severe disease or death.
Cristina Gervasoni, the infectious disease specialist from Luigi Sacco University Hospital who led that study, says she can’t explain the discrepancy between her findings and the new data. (The Italian cohort has now grown to 85 people with HIV, Gervasoni says, and the researchers still don’t see an elevated risk.) The South African population may differ in several ways from the Italian patients, including underlying medical problems, socioeconomic status, and access to health care, she says.
Salim Abdool Karim, director of the Centre for the AIDS Programme of Research in South Africa, says the data are reassuring. He worried the high TB and HIV rates meant the country’s population might be “decimated.” It’s not surprising that other countries weren’t able to detect such small increases in death risk, Karim says, given their lower rates of HIV infection. “When you get something that small, you generally don’t see it in populations where the disease is not common,” he says.
The study “gives an excellent idea as to who is at risk, and who we should invest resources in protecting,” adds Francois Venter, an HIV researcher at the University of the Witwatersrand, Johannesburg. “It really seems—similar to elsewhere—that if you have diabetes or hypertension, or you are older, you should be far more careful, and we should funnel resources to protect people like that.”
One puzzle is why people whose HIV was controlled with antiretroviral drugs were as likely to die as people living with uncontrolled HIV. That’s unexpected, Davies says, because people with uncontrolled HIV have compromised immune systems, and might be expected to fare worse with COVID-19. The finding could be down to “a glitch in the data,” Wilkinson says. But it could also support suspicions that impaired T cells, immune cells that are compromised in HIV-positive people regardless of whether they are on treatment, might worsen COVID-19. “That could be an explanation,” he says.