In epidemiology, a non-pharmaceutical intervention (NPI) is any method used to reduce the spread of an epidemic disease without requiring pharmaceutical drug treatments. Examples of non-pharmaceutical interventions that reduce the spread of infectious diseases include wearing a face mask and staying away from sick people. [1]
The US Centers for Disease Control and Prevention (CDC) points to personal, community, and environmental interventions. [2] NPIs have been recommended for pandemic influenza at both local [3] and global levels [4] and studied at large scale during the 2009 swine flu pandemic [5] and the COVID-19 pandemic. [6] [7] [8] NPIs are typically used in the period between the emergence of an epidemic disease and the deployment of an effective vaccine. [9]
Choosing to stay home to prevent the spread of symptoms of a potential sickness, covering coughs and sneezes, and washing one's hands regularly, are all examples of non-pharmaceutical interventions. [10] Another example is when administrators of schools, workplaces, community areas, etc., take proper preventive actions and remind people to take precautions when need be in order to avoid the spread of disease. [10] Most NPIs are simple, requiring little effort to put into practice, and, if implemented correctly, have the potential to save lives.
In the past, suggestions have been made that covering the mouth and nose, like with an elbow, tissue, or hand, would be a viable measure towards reducing the transmissions of airborne diseases. This method of source control was suggested, but not empirically tested, in the "Control of Airborne Infection" section of a 1974 publication of Riley's Airborne Infection. [16] NIOSH also noted that the use of a tissue as source control, in their guidelines for TB, had not been tested as of 1992. [17]
In 2013, Gustavo et al. looked into the effectiveness of various methods of source control, including via the arm, via a tissue, via bare hands, and via a surgical mask. They concluded that simply covering a cough was not an effective method of stopping transmission, and a surgical mask was not effective at reducing the amount of displaced droplets detected compared to the other rudimentary forms of source control. [18] Another paper noted that the fit of a face mask matters in its source control performance. [19] (However, note that OSHA 29 CFR 1910.134 does not cover the fit of face masks other than NIOSH-approved respirators. [20] )While source control protects others from transmission arising from the wearer, personal protective equipment protects the wearer themselves. [21] Cloth face masks can be used for source control (as a last resort) but are not considered personal protective equipment [22] [21] as they have low filter efficiency (generally varying between 2–60%), although they are easy to obtain and reusable after washing. [23] There are no standards or regulation for self-made cloth face masks, [24] and source control on a well-fitted cloth mask is worse than a surgical mask. [25]
Surgical masks are designed to protect against splashes and sprays, [26] but do not provide complete respiratory protection from germs and other contaminants because of the loose fit between the surface of the face mask and the face. [27] Surgical masks are regulated by various national standards to have high bacterial filtration efficiency (BFE). [28] [29] [30] N95/N99/N100 masks and other filtering facepiece respirators can provide source control in addition to respiratory protection, but respirators with an unfiltered exhalation valve may not provide source control and require additional measures to filter exhalation air when source control is required. [26] [31]Germs can survive outside the body on hard surfaces for periods ranging from hours to weeks, depending on the virus and environmental conditions. The disinfection of high-touch surfaces with substances such as bleach or alcohol kills germs, preventing indirect contact transmission. Dirty surfaces should be washed before the use of disinfectant. [9] [32]
Ultraviolet (UV) light can be used to destroy micro-organisms that exist in the environment. The installation of UV light fixtures can be costly and time consuming; it is unlikely that they could be used at the outbreak of an epidemic. There are possible health concerns involving UV light, as it may cause cancer and eye problems. The WHO does not recommend its use. [9]
Increased ventilation of a room through opening a window or through mechanized ventilation systems may reduce transmission within the room. Although opening a window may introduce allergens and air pollution, or, in some climates, cold air, it is overall a cheap and effective type of intervention, and its advantages probably outweigh its disadvantages. [9]
Viruses such as influenza and coronavirus thrive in cold, dry environments, and increasing the humidity of a room may reduce their transmission. [33] Higher humidity, however, may cause mold and mildew, which may in turn cause respiratory problems. Humidifiers are also expensive and will probably be in short supply at the start of an epidemic. [9]
Quarantine involves the voluntary or imposed confinement of potentially non-ill persons who have been exposed to an illness, regardless of whether they have contracted it. Quarantine will often happen at home, but it may happen elsewhere, such as aboard ships (maritime quarantine) or airlines (onboard quarantine). Like isolation of sick individuals, forced quarantine of exposed individuals brings with it ethical concerns, although in this case the concerns may be greater; quarantine involves restricting the movement of those who may otherwise be well, and in some cases may even cause them greater risk if they are quarantining with the sick person to whom they were exposed, such as a sick family member or roommate with whom they live. Like isolation, quarantine brings with it financial risk, because of work absenteeism. [9]
Measures taken involving schools range from making changes to operations within schools to complete school closures. Lesser measures may involve reducing the density of students, such as by distancing desks, cancelling activities, reducing class sizes, or staggering class schedules. Sick students may be isolated from the greater student body, such as by having them stay at home or otherwise segregate them from other students.
More drastic measures include class dismissal, in which classes are cancelled but the school stays open to provide childcare to some children, and complete school closure. Both measures may be either reactive or proactive: In a reactive case, the measure takes place after an outbreak has occurred in the school; in a proactive case, the measure takes place in order to prevent spread within the community.
Closures of schools may affect the families of affected children, especially low-income families. Parents may be forced to miss work to care for their children, affecting financial stability; children may also miss out on free school meals, causing nutritional concerns. Long absences from schools because of closures can also have negative effects on students' education. [9]
However, in the months following the onset of the COVID-19 pandemic, instead of closures, remote learning was turned to as an intervention against infection by SARS-CoV-2 in the days before vaccines. [36]
Measures taken in the workplace include: remote work; paid leave; staggering shifts such that arrival, exit, and break times are different for each employee; reduced contact; and extended weekends.
Workplace closure is a more drastic measure. The financial effect of workplace closure on both the individual and the economy can be severe. When remote work is not possible, such as in essential services, businesses may not be able to comply with guidelines. In one simulation study school closure coupled with 50% absenteeism in the workplace would have had the highest financial impact of all the scenarios studied, although some studies have found that the combination would be effective in reducing both the attack rate and the height of an epidemic.
One benefit of workplace closure is that when used in conjunction with school closures they avoid the need for parents to make childcare arrangements for children who are staying away from school.
The WHO recommends workplace closure in the case of extraordinarily severe epidemics and pandemics. [9]
Avoiding crowding may involve: avoiding crowded areas such as shopping centres and transportation hubs; closing public spaces and banning large gatherings, such as sports events or religious activities; or setting a limit on small gatherings, such as limiting them to no more than a few people. There are negative consequences to the banning of gatherings; banning cultural or religious activities, for example, may prevent access to support in a time of crisis. Gatherings also allow sharing of information, which can provide comfort and reduce fear.
The WHO recommends this intervention in moderate and severe epidemics and pandemics. [9]
Travel advice involves notifying potential travelers that they may be entering a zone that is affected by a disease outbreak. It allows informed decisions to be made before travel, and it increases awareness when the traveler is in the destination country. Public awareness campaigns have been used in the past for areas affected by infectious diseases such as dengue, malaria, Middle East respiratory syndrome, and H1N1 influenza. Although such awareness campaigns may reduce exposure among those traveling abroad, they may cause economic impact, owing to reduced travel in countries about which the advice has been issued. Overall, this intervention type is considered both feasible and acceptable. [9]
Entry and exit screening involves screening travelers at ports of entry for symptoms of illness. Measures include: health declarations, in which travelers make a declaration that they have not recently had symptoms of illness; visual inspections of the traveler; and the use of non-contact thermography, in which a device such as a thermographic camera is used to measure the traveler's body temperature, in order to determine if they have a fever. Such a method may be circumvented by the traveler through the use of antipyretics before travel in order to reduce fever. More intensive measures such as molecular diagnostics and point-of-care rapid antigen detection tests may also be used, but they carry a high resource cost and may not be applicable to a large number of travelers. A substantial number of resources may be needed in order to train staff and acquire equipment.
Although there is probably no harm to the traveler by the use of this type of intervention, a limitation of it is that travelers may be asymptomatic on arrival and symptoms may not show until several days after entry, at which point they may have already exposed others to their illness. There are also ethical concerns involving invading the privacy of the traveler. Screening is considered by the WHO to be both acceptable and feasible, though they did not recommend its use in the case of influenza outbreak due to its inefficacy in identifying asymptomatic individuals. [9]
Travel within a country may be restricted in order to delay the spread of disease. Restriction of travel within a country is likely to slow the spread of disease, but not prevent it entirely. Its use would be most effective at the start of a localized and extraordinarily severe pandemic for only a short period of time. It would only be effective if the measures were strict: while a 90% restriction was projected to delay spread by one or two weeks, a 75% restriction saw no effect. An analysis of the spread of influenza in America following complete airline closures due to the September 11 attacks saw reduced spread by 13 days compared with previous years.
Restricting travel brings both ethical, and in many countries, legal challenges. Freedom of movement is considered in many places to be a human right, and its restriction may have an adverse effect, particularly among vulnerable populations, such as migrant workers and those traveling to seek medical attention. Although 37% of the Member States of the WHO included internal travel restrictions as part of their pandemic preparedness plan as of 2019, some of those countries may face legal challenges in implementing them, because of their own laws. Such restrictions may also bring economic effects because of disruption in the supply chain. [9]
Border closure is a measure that involves complete or severe restriction of travel across borders. This had a beneficial effect in delaying the spread of cases of influenza during the 1918 influenza pandemic, and was predicted to delay epidemic spread between Hong Kong and mainland China by 3.5 weeks. While border closure is expected to slow the spread of infection, it is not expected to reduce the duration of an epidemic. Strict border closure in island nations could be effective, although supply chain problems may cause adverse disruptions.
Supply chain problems due to border closure are likely to cause disruption of essential goods, such as food and medications, as well as serious economic effects. They may have adverse effects on the daily lives of individuals. Border closure also has serious ethical implications, because, like internal travel restrictions, it involves restricting the movements of individuals. It should only be used as a voluntary measure to the maximum extent possible. There may also be stigmatization of individuals from affected areas.
Border closure would be most feasible at the very start of a pandemic. The WHO recommended it only in extraordinary circumstances, and asked that they be notified by any nation implementing it. [9]
Non-pharmaceutical interventions were widely adopted during the 1918 flu outbreak – most famously, the radical quarantine of Gunnison, Colorado resulted in sparing the town the worst of the earlier waves of the pandemic. [1] Interventions used included the wearing of face masks, isolation, quarantine, personal hygiene, use of disinfectants, and limits on public gatherings. At the time, the science behind NPIs was new, and was not applied consistently in every area. Retroactive studies on the outbreak have shown that the measures were effective in mitigating the spread of the infection. [37] [38]
The use of non-pharmaceutical interventions during the 1918 flu pandemic also gave rise to new societal concerns. There was a growing awareness of "overreacting" and "under-reacting" among U.S. public health authorities, and these opposing perspectives often added to the uncertainties inherent in the epidemic. Likewise, public perceptions varied with respect to adherence to public health guidelines, giving rise to terms such as "mask slackers" and "careless consumptives." [39]
COVID-19 is a disease caused by the SARS-CoV-2 virus, which spread from China, creating a pandemic. [40] Several COVID-19 vaccines are now being used, 6.54 billion doses having been administered worldwide as of 12 October 2021. [41]
In the early stages of the COVID-19 pandemic, before vaccines had been developed, NPIs were key in mitigating infections and reducing COVID-19-related mortality. Some NPIs remained in place or were reinstituted for a time after vaccine rollout. [42] One report identified over 500 specific NPIs for controlling transmission and spread of the SARS-CoV-2 virus; most of these have been tried in practice. [8] Evidence suggests that highly effective strategies include closing schools and universities, [43] banning large gatherings, [43] and wearing face masks. [44]
NPIs are still key to mitigating infections. NPIs, which include engineering controls under the Hierarchy of hazard controls, do not require compliance with PPE mandates, or require administrative changes, like lockdowns, to prevent the spread of disease among the general public.
The CDC suggests that, in non-healthcare settings, building ventilation should be brought up to 5 air changes per hour, along with the use of MERV-13 filters, the use of air purifiers (air cleaners), and upper-room Ultraviolet germicidal irradiation (UVGI) to reduce the odds of infection and people coming down with COVID-19. [45] [46] The UVGI systems are said to be similar to the UVGI systems used against tuberculosis in the past in healthcare facilities. [47] [46] As for ventilation, a survey conducted under 1989 ASHRAE standards showed that, of the buildings constructed in prior years and surveyed, all but one did not meet the recommended 5 ACH. [48]
Corsi–Rosenthal Boxes have been suggested as a viable temporary air cleaner. When tested by NIOSH, the boxes were found to reduce aerosols up to 73%, but most did not operate below noise standards. [49]These fixtures have been suggested as forms of "engineering controls" in the Hierarchy of hazard controls:
A pandemic is an epidemic of an infectious disease that has a sudden increase in cases and spreads across a large region, for instance multiple continents or worldwide, affecting a substantial number of individuals. Widespread endemic diseases with a stable number of infected individuals such as recurrences of seasonal influenza are generally excluded as they occur simultaneously in large regions of the globe rather than being spread worldwide.
An epidemic is the rapid spread of disease to a large number of hosts in a given population within a short period of time. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.
Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the virus SARS-CoV-1, the first identified strain of the SARS-related coronavirus. The first known cases occurred in November 2002, and the syndrome caused the 2002–2004 SARS outbreak. In the 2010s, Chinese scientists traced the virus through the intermediary of Asian palm civets to cave-dwelling horseshoe bats in Xiyang Yi Ethnic Township, Yunnan.
A surgical mask, also known by other names such as a medical face mask or procedure mask, is a personal protective equipment used by healthcare professionals that serves as a mechanical barrier that interferes with direct airflow in and out of respiratory orifices. This helps reduce airborne transmission of pathogens and other aerosolized contaminants between the wearer and nearby people via respiratory droplets ejected when sneezing, coughing, forceful expiration or unintentionally spitting when talking, etc. Surgical masks may be labeled as surgical, isolation, dental or medical procedure masks.
In epidemiology, the basic reproduction number, or basic reproductive number, denoted , of an infection is the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection. The definition assumes that no other individuals are infected or immunized. Some definitions, such as that of the Australian Department of Health, add the absence of "any deliberate intervention in disease transmission". The basic reproduction number is not necessarily the same as the effective reproduction number , which is the number of cases generated in the current state of a population, which does not have to be the uninfected state. is a dimensionless number and not a time rate, which would have units of time−1, or units of time like doubling time.
An influenza pandemic is an epidemic of an influenza virus that spreads across a large region and infects a large proportion of the population. There have been five major influenza pandemics in the last 140 years, with the 1918 flu pandemic being the most severe; this is estimated to have been responsible for the deaths of 50–100 million people. The 2009 swine flu pandemic resulted in under 300,000 deaths and is considered relatively mild. These pandemics occur irregularly.
In health care facilities, isolation represents one of several measures that can be taken to implement in infection control: the prevention of communicable diseases from being transmitted from a patient to other patients, health care workers, and visitors, or from outsiders to a particular patient. Various forms of isolation exist, in some of which contact procedures are modified, and others in which the patient is kept away from all other people. In a system devised, and periodically revised, by the U.S. Centers for Disease Control and Prevention (CDC), various levels of patient isolation comprise application of one or more formally described "precaution".
Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
The 2009 swine flu pandemic, caused by the H1N1/swine flu/influenza virus and declared by the World Health Organization (WHO) from June 2009 to August 2010, was the third recent flu pandemic involving the H1N1 virus. The first identified human case was in La Gloria, Mexico, a rural town in Veracruz. The virus appeared to be a new strain of H1N1 that resulted from a previous triple reassortment of bird, swine, and human flu viruses which further combined with a Eurasian pig flu virus, leading to the term "swine flu".
In public health, social distancing, also called physical distancing, is a set of non-pharmaceutical interventions or measures intended to prevent the spread of a contagious disease by maintaining a physical distance between people and reducing the number of times people come into close contact with each other. It usually involves keeping a certain distance from others and avoiding gathering together in large groups.
Airborne transmission or aerosol transmission is transmission of an infectious disease through small particles suspended in the air. Infectious diseases capable of airborne transmission include many of considerable importance both in human and veterinary medicine. The relevant infectious agent may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, raising of dust, spraying of liquids, flushing toilets, or any activities which generate aerosol particles or droplets.
Influenza prevention involves taking steps that one can use to decrease their chances of contracting flu viruses, such as the Pandemic H1N1/09 virus, responsible for the 2009 flu pandemic.
Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the coronavirus SARS-CoV-2. The disease spread worldwide, resulting in the COVID-19 pandemic.
Neil Morris Ferguson is a British epidemiologist and professor of mathematical biology, who specialises in the patterns of spread of infectious disease in humans and animals. He is the director of the Jameel Institute, and of the MRC Centre for Global Infectious Disease Analysis, and head of the Department of Infectious Disease Epidemiology in the School of Public Health and Vice-Dean for Academic Development in the Faculty of Medicine, all at Imperial College London.
Hazard controls for COVID-19 in workplaces are the application of occupational safety and health methodologies for hazard controls to the prevention of COVID-19. Multiple layers of controls are recommended, including measures such as remote work and flextime, personal protective equipment (PPE) and face coverings, social distancing, and enhanced cleaning programs. Recently, engineering controls have been emphasized, particularly stressing the importance of HVAC systems meeting a minimum of 5 air changes per hour with ventilation or MERV-13 filters, as well as the installation of UVGI systems in public areas.
Outbreak response or outbreak control measures are acts which attempt to minimize the spread of or effects of a disease outbreak. Outbreak response includes aspects of general disease control such as maintaining adequate hygiene, but may also include responses that extend beyond traditional healthcare settings and are unique to an outbreak, such as physical distancing, contact tracing, mapping of disease clusters, or quarantine. Some measures such as isolation are also useful in preventing an outbreak from occurring in the first place.
During the COVID-19 pandemic, face masks or coverings, including N95, FFP2, surgical, and cloth masks, have been employed as public and personal health control measures against the spread of SARS-CoV-2, the virus that causes COVID-19.
The COVID-19 pandemic has had many impacts on global health beyond those caused by the COVID-19 disease itself. It has led to a reduction in hospital visits for other reasons. There have been 38 per cent fewer hospital visits for heart attack symptoms in the United States and 40 per cent fewer in Spain. The head of cardiology at the University of Arizona said, "My worry is some of these people are dying at home because they're too scared to go to the hospital." There is also concern that people with strokes and appendicitis are not seeking timely treatment. Shortages of medical supplies have impacted people with various conditions.
Source control is a strategy for reducing disease transmission by blocking respiratory secretions produced through breathing, speaking, coughing, sneezing or singing. Multiple source control techniques can be used in hospitals, but for the general public wearing personal protective equipment during epidemics or pandemics, respirators provide the greatest source control, followed by surgical masks, with cloth face masks recommended for use by the public only when there are shortages of both respirators and surgical masks.
Part of managing an infectious disease outbreak is trying to delay and decrease the epidemic peak, known as flattening the epidemic curve. This decreases the risk of health services being overwhelmed and provides more time for vaccines and treatments to be developed. Non-pharmaceutical interventions that may manage the outbreak include personal preventive measures such as hand hygiene, wearing face masks, and self-quarantine; community measures aimed at physical distancing such as closing schools and cancelling mass gathering events; community engagement to encourage acceptance and participation in such interventions; as well as environmental measures such surface cleaning. It has also been suggested that improving ventilation and managing exposure duration can reduce transmission.
The results showed that cloth masks and other fabric materials tested in the study had 40–90% instantaneous penetration levels against polydisperse NaCl aerosols employed in the National Institute for Occupational Safety and Health particulate respirator test protocol at 5.5 cm s−1.