Roughly one-quarter of the world's population has been infected with M. tuberculosis,^[6] with new infections occurring in about 1% of the population each year.^[12] However, most infections with M. tuberculosis do not cause disease,^[170] and 90–95% of infections remain asymptomatic.^[88] In 2012, an estimated 8.6 million chronic cases were active.^[171] In 2010, 8.8 million new cases of tuberculosis were diagnosed, and 1.20–1.45 million deaths occurred (most of these occurring in developing countries).^[79][172] Of these, about 0.35 million occur in those also infected with HIV.^[173] In 2018, tuberculosis was the leading cause of death worldwide from a single infectious agent.^[174] The total number of tuberculosis cases has been decreasing since 2005, while new cases have decreased since 2002.^[79]

Tuberculosis^{[clarification needed]} incidence is seasonal, with peaks occurring every spring and summer.^{[175][176][177][178]} The reasons for this are unclear, but may be related to vitamin D deficiency during the winter.^[178][179] There are also studies linking tuberculosis to different weather conditions like low temperature, low humidity and low rainfall. It has been suggested that tuberculosis incidence rates may be connected to climate change.^[180]

Mycobacteria infect many different animals, including birds,^[255] fish, rodents,^[256] and reptiles.^[257] The subspecies Mycobacterium tuberculosis, though, is rarely present in wild animals.^[258] An effort to eradicate bovine tuberculosis caused by Mycobacterium bovis from the cattle and deer herds of New Zealand has been relatively successful.^[259] Efforts in Great Britain have been less successful.^[260][261]

As of 2015, tuberculosis appears to be widespread among captive elephants in the US. It is believed that the animals originally acquired the disease from humans, a process called reverse zoonosis. Because the disease can spread through the air to infect both humans and other animals, it is a public health concern affecting circuses and zoos.^[262][263]

Conclusion

Tuberculosis after recovering from COVID-19 is becoming more common, potentially leading to a TB outbreak in the post-COVID-19 era. The immunosuppressive nature of the disease and its treatment modalities may contribute to post COVID-19 TB. Thus, we recommend a further study with a large sample size. Furthermore, we recommend feasibility studies to assess and treat latent TB in COVID-19 patients residing in TB endemic counties since treatment of latent TB is done only in TB non-endemic countries.