Recurrence of COVID-19 infection symptoms in short time; reinfection or reactivation? Three cases of three healthcare workers and a literature review.

Background: Since the beginning of the COVID-19 pandemic, many research papers have been published focusing on some recurrence cases of symptoms after a long period of free symptoms with a negative RT-PCR retest. There is no crucial evidence until now of the possibility of recurrence, immune system reactivation, or reinfection. Methods: Three cases of resident doctors who recovered from COVID-19 but represented symptoms with new positive RT-PCR were discussed. Clinical data, laboratory tests, RT-PCR results, and antibodies titers all were collected. Moreover, many cases from the literature have been reviewed and compared. Results: The long-term exposure has not succeeded in forming an effective immune response, especially, since they do not have any significant history of chronic illnesses or a diagnosed immune disorder. While the antibody response occurred only in the second patient, it did not prevent new infection, but did it control the severity of the infection or its complications? Conclusion: Our three patients are health workers and have been in direct contact with COVID-19 patients. The inflammatory response parameters may not be reliable in predicting the activation of the immune response and the formation of the antibodies. We still need to find answers for reactivation and reinfection issues.

DIMY: Enabling privacy-preserving contact tracing.

The infection rate of COVID-19 and the rapid mutation ability of the virus has forced governments and health authorities to adopt lockdowns, increased testing, and contact tracing to reduce the virus's spread. Digital contact tracing has become a supplement to the traditional manual contact tracing process. However, although several digital contact tracing apps are proposed and deployed, these have not been widely adopted due to apprehensions surrounding privacy and security. In this paper, we present a blockchain-based privacy-preserving contact tracing protocol,"Did I Meet You" (DIMY). The protocol provides full-lifecycle data privacy protection on the devices as well as the back-end servers to address most of the privacy concerns associated with existing protocols. We have employed Bloom filters to provide efficient privacy-preserving storage and have used the Diffie-Hellman key exchange for secret sharing among the participants. We show that DIMY provides resilience against many well-known attacks while introducing negligible overheads. DIMY's footprint on the storage space of clients' devices and back-end servers is also significantly lower than other similar state-of-the-art apps.

A Survey of COVID-19 Contact Tracing Apps

The recent outbreak of COVID-19 has taken the world by surprise, forcing lockdowns and straining public health care systems. COVID-19 is known to be a highly infectious virus, and infected individuals do not initially exhibit symptoms, while some remain asymptomatic. Thus, a non-negligible fraction of the population can, at any given time, be a hidden source of transmissions. In response, many governments have shown great interest in smartphone contact tracing apps that help automate the difficult task of tracing all recent contacts of newly identified infected individuals. However, tracing apps have generated much discussion around their key attributes, including system architecture, data management, privacy, security, proximity estimation, and attack vulnerability. In this article, we provide the first comprehensive review of these much-discussed tracing app attributes. We also present an overview of many proposed tracing app examples, some of which have been deployed countrywide, and discuss the concerns users have reported regarding their usage. We close by outlining potential research directions for next-generation app design, which would facilitate improved tracing and security performance, as well as wide adoption by the population at large.