contact tracing contact tracing in public health, contact tracing is the process of identifying persons who may have been exposed to an infected person ("contacts") and subsequent collection of further data to assess transmission. by tracing the contacts of infected individuals, testing them for infection, and isolating or treating the infected, this public health tool aims to reduce infections in the population. in addition to infection control, contact tracing serves as a means to identify high-risk and medically vulnerable populations who might be exposed to infection and facilitate appropriate medical care. in doing so, public health officials utilize contact tracing to conduct disease surveillance and prevent outbreaks. in cases of diseases of uncertain infectious potential, contact tracing is also sometimes performed to learn about disease characteristics, including infectiousness. contact tracing is not always the most efficient method of addressing infectious disease. in areas of high disease prevalence, screening or focused testing may be more cost-effective. contact tracing attempts to find all contacts of a confirmed case, in order to test or monitor them for infection. the goal is to stop the spread of a disease by finding and isolating cases. the goals of contact tracing include: interrupting ongoing transmission and reduce the spread of an infection alerting contacts to the possibility of infection and offer preventive services or prophylactic care offering diagnosis, counseling and treatment to already infected individuals if the infection is treatable, helping prevent reinfection of the originally infected patient learning about the epidemiology of a disease in a particular population being a tool in multifaceted prevention strategy to effectively curb the spread of an infectious disease. visual depiction of disease spread with and without contact tracing. history contact tracing programs were first implemented to track syphilis cases in the 1930s. initial efforts proved to be difficult given the stigmatization associated with sexually transmitted infections (stis). individuals were reluctant to report infections because they were concerned for their privacy. revealing partner history and details about sexual activity was challenging as it affected relationships among individuals and community members. in addition, public health officials targeted certain populations such as sex workers, minorities, and at-risk populations further eliciting feeling of fear, shame, and guilt in society. with these negative implications of contact tracing, particularly in the space of sexually transmitted infections, public health officials found it difficult to elicit information from exposed individuals. during the hiv epidemic, many affected person were hesitant to report information, which hindered the efforts to understand hiv and curb the spread. to combat some of the negative stigma associated with contact tracing and stis, health departments sometimes referred to contact tracing as partner notification in the 1980s. partner notification, also called partner care, is a subset of contact tracing aimed specifically at informing sexual partners of an infected person and addressing their health needs. this definition evolved from identifying infected individuals to including a comprehensive program that encompasses counseling and medical care to treat the infection. the official title, contract tracers, was first implemented in the united kingdom during the smallpox outbreaks. dedicated individuals served on a surveillance-based team to curb the spread of disease. this process served as a blueprint for other public health agencies to have a formalized program. the united states soon followed and enacted a contact tracing program for the prevention of infectious diseases which included tb, hiv, sars, and now sars-cov-2. steps a visualization of contact tracing transmission chains contact tracing generally involves the following steps as provided by cdc: notification of exposure: an individual is identified as having a communicable disease (often called the index case). this case may be reported to public health or managed by the primary health care provider. ideally, all notification should be done within 24 hours of exposure. if contacts are not individually identifiable (e.g. members of the public who attended the same location), broader communications may be issued, like media advisories. communication with the contacts will be initially done through digital methods including texts and email. efforts to inform the contacts remotely should be exhausted before considering an in-person communication. during this process, it is imperative that the identity of the source of exposure must not be revealed to the contact. contact interview: the index case is interviewed to learn about their movements, whom they have been in close contact with or who their sexual partners have been. depending on the disease and the context of the infection, family members, health care providers, and anyone else who may have knowledge of the case's contacts may also be interviewed. interviews typically follow a template which include demographics, symptomology, pre-existing conditions, and timing of exposures to ensure consistency across all contact tracing efforts. interpreters and source materials in different languages are utilized to accommodate persons with different cultural backgrounds. recommendations for close contacts: once contacts are identified, public health workers contact them to offer counseling, screening, prophylaxis, and/or treatment. contacts are provided education on concepts of quarantine, isolation, signs and symptoms of disease, and timely testing. if applicable, contacts should wear appropriate personal protective equipment to reduce to transmission of disease. assessing feasibility of self-quarantine and support: contacts may be isolated (e.g. required to remain at home) or excluded (e.g. prohibited from attending a particular location, like a school) if deemed necessary for disease control. challenges for this process include access to resources during quarantine such as food, water, and safe living environment. people with special roles lack the convenience practicing quarantine given their daily responsibilities. examples include, single parents, caregivers, and individuals with toddlers. social services and ancillary support from the government become crucial to maintaining measures of quarantine and isolation. contacts should be made aware whether or not the quarantine or isolation is voluntary or mandatory. depending on the nature of the disease of interest, governments can issue legal orders to maintain integrity of contact tracing. medical monitoring: although contact tracing can be enhanced by letting patients provide information, medication, and referrals to their contacts, evidence demonstrates that direct public health involvement in notification is most effective. ideally, contacts are checked upon daily for signs and symptoms of disease by contact racers. an alternative would be having the contacts report daily to their assigned official. this is usually done through digital platforms such as email and text. if a contact is symptomatic, a case investigator is assignment to direct the individual to the appropriate testing and treatment. this stage of contact tracing is highly dependent on resource availability. contact close out: this stage is dependent on the duration of quarantine for people with and without symptoms. the ideal number of days for quarantine and isolation are determined by the health agencies. once the contact adequately completes the quarantine/isolation for the defined number of days, they can be closed out. next steps such as returning to work and participating in social activities are discussed. application contact tracing during a cholera outbreak in bangladesh (2014): fetp investigators interview the mother of an index case patient. backward versus forward contact tracing. contact types the types of contacts that are relevant for public health management vary because of differing modes of transmission. for sexually transmitted infections, sexual contacts of the index case are relevant, as well as any babies born to the index case. this information is crucial for investigating congenital syphilis cases for example. for blood-borne infections, blood transfusion recipients, contacts who shared a needle, and anyone else who could have been exposed to the blood of the index case are relevant. this information becomes relevant for health systems to keep track of high risk populations and medical errors, unavoidable and preventable. for pulmonary tuberculosis, people living in the same household or spending a significant amount of time in the same room as the index case are relevant. understanding the pathology and transmissibility of the disease guides the approach to contact tracing strategy. outbreaks although contact tracing is most commonly used for control of diseases, it is also a critical tool for investigating new diseases or unusual outbreaks. for example, as was the case with sars, contact tracing can be used to determine if probable cases are linked to known cases of the disease, and to determine if secondary transmission is taking place in a particular community. contact tracing has also been initiated among flight passengers during the containment phase of larger pandemics, such as the 2009 pandemic h1ni influenza. contact tracing played a major role in investigating ebola virus in the uk in 2014 and monkeypox in the uk in 2018. the eradication of smallpox, for example, was achieved by exhaustive contact tracing to find all infected persons. this was followed by isolation of infected individuals and immunization of the surrounding community and contacts at-risk of contracting smallpox. contact tracing can help identify the etiology of a disease outbreak. in 1984, contact tracing provided the first direct evidence that aids may be spread by an infectious agent during sexual contacts. the infective agent has since been identified as hiv. diseases for which contact tracing is commonly performed include tuberculosis, vaccine-preventable infections like measles, sexually transmitted infections (including hiv), blood-borne infections, ebola, bacterial infections, and novel virus infections (e.g., sars-cov, h1n1, and sars-cov-2). contact tracing has been a pillar of communicable disease control in public health for decades. with each outbreak and disease presenting with its own challenges, contact tracing is an adaptable tool used by authorities to identify, notify, and curb transmission of infections. a 1984 paper traced the sexual contacts of 40 early aids patients by sexual contact. the paper concluded that the spread of aids may be facilitated by the transfer of an infective agent during sexual contacts. backward and forward tracing backward (or reverse) tracing seeks to establish the source of an infection, by looking for contacts before infection. it can be used when a source of the infection is unknown and in situations of minimally monitored settings. the goal is identify the exposures associated with the index case and secondary exposures of those contact to halt the cycle of transmission. during the covid-19 pandemic, the adoption by japan in early spring 2020 of an approach focusing on backward contact tracing was hailed as successful, and other countries which managed to keep the epidemic under control, such as south korea and uruguay, are said to have also used the approach. forward tracing is the process of looking for contacts after infection, so as to prevent further disease spread. it is the more conventional way to investigate cases and inform close contacts to either quarantine or isolate. for epidemics with high heterogeneity in infectiousness, adopting a hybrid strategy of forward contact tracing combined with contact tracing backwards is often used. backward contact tracing is beneficial for identifying clusters of spreader events, while forward tracing can be used mitigate future transmission. the effectiveness of both approaches is limited by the resources dedicated to contact tracing. journalist and author laurie garrett pointed out in late october 2020, however, that the amount of the virus in the u.s. is now so large that no health departments has the resources to contact and trace. additionally, officials overlooked the effect of mistrust in the government and conspiracy theories regarding the virus on thwarting contact tracing efforts in the u.s. covid-19 contact tracing requires tremendous resources and work hours to effectively contain an infection. the covid-19 pandemic is an unprecedented period where contact tracing and public health efforts were put to the test. creative strategies were used to sustain public health efforts. non-health personnel and volunteers were used to meet the shortage of contact tracers. existing infrastructure such as call centers and national helpline services were used for operations. individuals who were the most sick and medically vulnerable were prioritized as contacts over healthier people. the advent of technology and digital tracing tools were implemented at a global scale without much vetting and testing. various countries had different adaptations and outcomes with contact tracing. china used pre-existing wechat and alipay platforms to track person health status and travel patterns. singapore, south korea, and vietnam had success limiting the initial spread of the virus. with contact tracing, once a person was identified to be exposed, they were immediately isolated. in some instances the government provided housing for isolation to limit movements. in turkey, the government launched a public