On average, 3027 ± 71 cases of TB are reported each quarter in Guinea, with a success rate of 83% ± 0.7 cases, for all periods of our series. Reported TB cases varied considerably during the period of EVD for all forms of TB including those clinically diagnosed (441 ± 139 cases) and confirmed bacteriologically (1849 ± 209 cases) on average (table1). The NTP TB case notification rate decreased from 120 cases per 100,000 population in 2011 to 100 cases per 100,000 population in 2014, resuming an upward trend from 2015 to 2018 (Figure 1). From 2012 to 2013, the trends were down slightly, but higher than in 2014. After this year, notifications of new cases and relapses for all forms of TB started to increase. The same is true for new clinically diagnosed cases, pulmonary relapses, and clinically confirmed cases and pulmonary relapses. The recovery of the upward trend just after the historic decline recorded in 2014 is very evident and continues to increase each year (Figure 1).
From 2011 to 2014, notification rates for all forms of TB cases ( F-value = 5.7 [95% CI: 0.2–21.3] and p-value = 0.024), bacteriologically confirmed and clinically diagnosed pulmonary cases showed negative variations, i.e., a decrease in the number of cases detected each year with a peak of –26 for bacteriologically confirmed TB cases in 2014. As of 2015, annual changes ranging from 7% for new TB cases clinically diagnosed to 17% for TB cases bacteriologically confirmed (Figure 1).
The analysis of the time series of NTP notifications shows essentially a gap with a much larger trough between 2014 and 2015 (F-value = 5.7 [95% CI: 0.2- 21.3] and p-value = 0.03 for EVD periods). From 2011 to 2018, cascades are observed over the years concerning the reported cases of TB in all forms in the range of 2000 to 4000 cases per quarter and vary from year to year. The periods between 2014 and 2015 reported the fewest cases (2000) compared to other years where at least 2500 cases were recorded (Figure 2).
For Ebola cases, the number of cases is less than 2,200, except for the last two quarters of 2014, which recorded up to 2949 cases (6 cases per 10,000 inhabitants) in total, only 4000 cases of TB were reported during this period. The low reporting period of TB was between 2014 and 2015 (EVD period). Between July 2014 and January 2015, fewer TB cases (2,200 or 94 per 100,000 population) were reported in January and July 2014, increasing to more than 3,000 cases (117 cases per 1,000 cases) in the first quarter of 2015 as the EVD began its decline. Examining all forms of TB, cases exceed 2,500 (96 cases per 1,000 inhabitants) per quarter, but these trends were decreasing in 2014.
The TB treatment success rate has gradually increased over the years, despite the seriousness of the EVD outbreak. The outcome indicators did not significantly change during the EVD period despite their slight decrease (F-value = 10.9 [95% CI: 0.3 –36.8] and p-value = 0.015); success rates were lowest (76%) in the first quarter of 2014 (Table 3).
The incidence of EVD rapidly changed—increasing and then decreasing, with the most significant proportion occurring before 2014 (more than 500 cases). The incidence of TB decreased by 1,500 cases between 2014 and 2015 before fluctuating the following year positively and then remaining until 2016.
The cross-correlation test between the time series of TB and EVD (table 2; figure 2) shows a significant delay of –0.4 (40%) for all forms of TB, corresponding to the sharp decline in the incidence of TB observed at the height of the EVD outbreak in 2014 (Figure 2). The ANCOVA model (table 3) confirms this shift with a p-value of the adjusted value of the F-value <0.01. However, although the offsets are observed for the other forms of TB by looking at them separately, these offsets are not significant according to the regression model of the interrupted time series (adjusted p-value of F-value> 0.05) despite the seasonal adjustment of the time series (table 3). The number of reported cases of TB, all forms combined, increased (figure 2) from an average of 2909 cases per 100,000 before the EVD outbreak to 3,500 cases per quarter after the EVD outbreak (table 4), representing a 21% increase (F-values = 11.43 95% CI [0.30–44.07 and p-Value = 0.002]). This increase is quite remarkable considering the therapeutic success rate, which averaged 82% before the EVD outbreak and 89% the EVD outbreak (F-value = 21.9 95% CI [8.9–47.5]) and p-value <0.001).
Regarding the TB surveillance system, of the 13 standards and criteria developed by WHO, five were achieved by the NTP in 2019, compared to only three in 2015 (Table 5). This means that the surveillance system deserves targeted, long-term action to meet the challenge of screening and monitoring patients on treatment.