Despite years of experience, the Centers for Disease Control and Prevention (CDC) has not yet been able to translate its success in contact tracing cases of tuberculosis (TB), to tracing cases of COVID-19.

While both infectious diseases share some similar modes of transmission, and therefore require the same expertise in tracing contacts, COVID-19 tracers are hampered by three things: (l) the disease’s sheer swiftness in spreading; (2) trust issues between contact tracers and the community; and (3) mixed messages coming out of Washington.

But the effort continues. In January, the CDC diverted all resources from TB control programs to COVID-19 tracing efforts. And the steps being taken to identify contacts of people with COVID-19 are being taken from the TB tracing rulebook.

TB and COVID-19, also called coronavirus disease, have some similarities and some big differences. Both diseases are generally transmitted via the air. But TB has been around for millennia. Egyptian mummies bore the skeletal scars of bone tuberculosis; these deformities even were depicted in Egyptian art. Not so, with COVID-19.

“COVID-19 is a novel disease, and [the] science around this is still emerging," CDC spokesperson Jacqueline Petty told Medical Daily. She attributed her comments to CDC experts.

To Americans, TB may seem like a disease of the past. On the contrary, the CDC estimates that, in 2019, there were 8,920 new TB cases. As for the novel coronavirus, about 6.92 million COVID-19 positive cases and 201,000 deaths have been reported since the pandemic started.

One major difference between the two diseases is the asymptomatic issue. Carriers of the coronavirus can infect others; people with latent tuberculosis cannot, according to the CDC. “I think that the pace of COVID-19 and the fact that asymptomatic transmission can happen make contact tracing particularly difficult,’’ Donna Hope Wegener, executive director of the National TB Controllers Association (NTCA) told Medical Daily.

How the CDC adapted TB contact tracing

In the CDC’s TB program, tracers assess the TB patients’ household contacts, followed by the locations they have visited recently. A lot goes into this assessment. Tracers look at “structure of the exposure setting, proximity, duration, frequency of exposure and infectiousness of the patient,” said Ms. Petty. “This information is then used to prioritize follow-up of contacts and recommendations for testing and treatment.”

This is a lot easier to do with 8,920 cases of TB. Facing millions of potential COVID-19 cases, some health departments have had to revisit the drawing board.

“A number of state and local health departments have created multi-disciplinary response teams to conduct facility assessments and contact tracing activities in congregate, high-density, high-occupancy settings, such as schools, bars, restaurants and group homes,” according to the CDC.

Ms. Wegener said this approach makes sense, since the same human and fiscal resources are needed to conduct both TB and COVID-19 contact tracing. “On the fiscal side, resources are needed to adequately staff a contact investigation team. On the human resource side, it involves highly trained individuals with knowledge to determine the period of potential infectiousness and the environmental conditions leading to prolonged exposure,” that is, the size of shared space and length of time in the space, Ms. Wegener said.

Failures of COVID-19 contact tracing

The trust factor . Despite the experience and training that health care staff possess, finding all contacts of COVID-19 patients remains challenging. Trust needs to be established over time to make communities understand the importance of sharing names and providing information pertaining to people who have been exposed. “Getting people to trust you doesn’t often happen in minutes, and a day or two makes a big difference,” Ms. Wegener said.

Testing confusion . Another factor derailing the investigation of contacts of COVID-19 patients is the rule prohibiting the testing of asymptomatic individuals. Until Sept. 18, the CDC guidelines did not recommend testing asymptomatic people, even if they had been within six feet of a COVID-19 positive person.

Virtual format. The CDC provides resources and information to help state and local health departments with contact investigations in a virtual environment, but shifting to the online medium took a while. Ann Cronin, associate director for policy and issues management in the CDC’s Division of TB Elimination, told Medical Daily: "TB contact investigations are often conducted through in-person visits and interviews, hence adapting these visits and interviews to virtual or phone-based platforms is challenging."

TB cases underreported in 2020

The assumption that TB is no longer an issue in the U.S. is largely due to the success of the U.S. national tuberculosis program, which has actively reported and monitored TB cases since 1953. From 1953 to 1984, cases dropped by almost 6% every year, on average. There was, however, an increase in numbers starting in 1985 and lasting until 1992, due to immigration from countries with a high level of TB cases, multidrug-resistant tuberculosis and the HIV epidemic. After this resurgence, there was a coordinated effort to contain the TB spread once again. One study estimated that approximately 145,000 to 319,000 cases were averted during from 1995 to 2014.

However, all these efforts might be thwarted by the hypervigilant coronavirus response. The CDC’s Morbidity and Mortality Weekly Report from July 24 said that the pandemic has strained public health services across sections, including TB control services. In April, 15% of health care workers reported difficulty in procuring TB medication.

Delays in diagnosis and contact tracing could lead to TB outbreaks in this inopportune time, according to the CDC journal. While exact numbers won’t be released until early 2021, the NTCA said there are enough anecdotal accounts to raise concern.

"CDC generally releases provisional TB data for the previous year in late March, so we do not yet know the full impact of the COVID-19 pandemic on [TB] case reporting," Ms. Cronin said.

Note: Part 3 of this series will include a global survey discussing further how the pandemic has affected TB health care.

Seema Prasad is a freelance health reporter based in Bengaluru, India. She tweets @SeemaPrasad_me