Non-pharmaceutical interventions, sometimes abbreviated as NPIs, are actions, apart from getting vaccinated and taking medicine, that people and communities can take to help slow the spread of infectious diseases and control epidemics. In this third part, I'm going to talk about isolation, quarantine, and contact tracing. The objectives of this session are: to define and distinguish isolation and quarantine; to describe considerations for implementation and duration of isolation, contact tracing, and quarantine; and to discuss the difference between quarantine and public health observation. Isolation and quarantine are some of the earliest recorded interventions to control infections, going back to biblical times, more than two and a half thousand years ago. The basic idea of isolation is to reduce the chance of transmission from an infected person to other patients, health care staff, or visitors. Isolation is typically used for serious infections, and takes place in special hospital facilities such as negative pressure rooms, where access to the patient can be tightly controlled. For less serious diseases, such as measles and chickenpox, cases can be isolated at home. For isolation to be most effective, it should be done while the case is infectious, i.e. during the infectious period. Therefore isolation is most effective as a public health measure when cases can be rapidly identified and diagnosed. Control of the SARS epidemic in 2003 coincided with shortening in the median time to admission and isolation of cases, along with effective infection control procedures in hospitals. Quarantine refers to the detention of exposed and potentially infected persons for close observation until it is apparent that they have not been infected. Persons who show signs of infection during quarantine will typically be moved to isolation. In Europe in the 14th century, an epidemic of Black Death wiped out 30% of the population, and many cities took measures to prevent introduction of the disease. The word "quarantine" is derived from the Italian word for 40, since some cities required visitors to stay for 40 days in an enclosed location, such as an island, before being allowed into the city. In order for quarantine to be effective, potentially exposed persons must be observed for the duration of the potential incubation period. In the case of SARS, the mean incubation period was around five days, and a quarantine period of 14 days would capture more than 95% of incubations. In the case of Ebola virus, the mean incubation period is 11 days, and 95% of infections lead to symptoms within 21 days. It is important to be clear on the difference between isolation and quarantine. Isolation is used for infectious individuals who are typically symptomatic, while quarantine is used for persons who have been exposed and might be infected, but are not thought to be infectious. Both isolation and quarantine aim to prevent infectious individuals from spreading infection to others. Now, in order to identify persons who have been exposed to infection, and therefore should be quarantined, it is often necessary to do contact tracing. The number and type of contacts to be traced depends on the mode in which infection occurs. For respiratory viruses such as SARS, the most important people to identify are those who have had prolonged close contact, such as family members, classmates, or work colleagues, and health care workers that came into contact with the case. In some cases it can be difficult to identify contacts, and instead much broader criteria are used. For example, in Hong Kong, an outbreak of SARS in a residential apartment block in 2003 led to quarantine of all residents for two weeks. While in 2009, identification of an imported case of H1N1 in a tourist led to a seven-day quarantine of the entire hotel he was staying at. Contact tracing is usually done by public health officials but in some emergencies it may be necessary to involve others. For example, in the SARS epidemic in 2003, contact tracing in Hong Kong was done by police force, while in Singapore it was done by the military. In some diseases which are less serious or which have longer incubation periods, quarantine can be impractical, and instead those people who are exposed and potentially infected are kept under public health observation but allowed to stay at home or even to go about their daily activities rather than being placed in a quarantine facility. Public health observation would typically involve regular visits or telephone calls to check whether the person had developed any symptoms. Thinking about the current epidemic of Ebola virus disease in West Africa, the most effective tools to control the epidemic are isolation of the ill, and quarantine or observation of exposed persons. And one of the factors contributing to the scale of the epidemic has been the lack of resources to trace and observe contacts, and to rapidly isolate cases in some areas. Public health monitoring of exposed persons and isolation of cases has been able to halt Ebola virus disease outbreaks in Nigeria and Senegal during the current outbreak, and prior Ebola outbreaks in Congo and Uganda. Another contributing factor to the scale of the current outbreak is the limited capacity for infection control in health care settings, leading to infection and in many cases the death of health care workers. One additional factor which may be controversial is the idea that quarantine policies earlier in the epidemic contributed to the speed of geographic spread of Ebola virus disease in Liberia. The argument goes like this-- faced with the prospect of being confined for three weeks with other potentially infected persons, some exposed people fled affected areas rather than complying with quarantine. In this case, medical observation rather than strict quarantine may be more acceptable, and consequently more effective.
