Source: accessed 5/17/07 http://www.pandemicflu.gov/plan/healthcare/maskguidancehc.html
Modes of Influenza Transmission
Influenza is transmitted person to person through close contact. Transmission occurs through multiple routes, including large droplets and direct and indirect contact. Fine droplet inhalational transmission may also occur.
Most information on the modes of influenza transmission from person to person is indirect and largely obtained through analysis of outbreaks in health care facilities and other settings (e.g., cruise ships, airplanes, schools, and colleges). Although the knowledge base is limited, the epidemiologic pattern observed is consistent with transmission through close contact (i.e., exposure to large respiratory droplets, direct contact transfer of virus from contaminated hands to the nose or eyes, or exposure to small-particle aerosols in the immediate vicinity of the infectious individual [known as “short-range exposure to aerosols”]). The relative contributions and clinical importance of the different modes of influenza transmission are unknown. While some observational studies and animal studies raise the possibility of short-range airborne transmission through small-particle aerosols, convincing evidence of airborne transmission of influenza viruses from person to person over long distances (e.g., through air-handling systems, or beyond a single room) has not been demonstrated. However, one study in mice performed in a room outfitted with a slowly rotating fan to continuously agitate the air found that influenza virus sprayed into the room remained infective for some mice for extended periods (up to 24 hours) at room atmospheres of low humidity (17 to 24%). Room atmospheres with higher humidities into which virus suspension was sprayed were no longer infective in mice after one hour (3).
Droplet Transmission
Droplet transmission involves contact of the mucous membranes of the nose or mouth or the conjunctivae of a susceptible person with large-particle droplets containing microorganisms generated by an infected person during coughing, sneezing, or talking. Transmission via large-particle droplets requires close contact between source and recipient persons because these larger droplets do not remain suspended in the air and generally travel only short distances. Three feet has often been used by infection control professionals as a guide for “short distance” and is based on studies of respiratory infections;however, for practical purposes, this distance may range from three to six feet. Special air handling and ventilation are not required to prevent droplet transmission.
On the basis of epidemiologic patterns of disease transmission, large droplet transmission—via coughing and sneezing—has traditionally been considered a major route of seasonal influenza transmission
>>Airborne Transmission
Airborne transmission occurs by dissemination of small particles or droplet nuclei[b] through the air (see Appendix A: Aerosol Science and Disease Transmission). Some organisms (e.g., Mycobacterium tuberculosis, measles virus, and varicella [chickenpox] virus) can remain infectious while dispersed over long distances by air currents, causing infection in susceptible individuals who have not had face-to-face contact (or been in the same room) with the infectious individual. Special air handling and ventilation systems (e.g., negative-pressure rooms or airborne isolation rooms) are used in health care settings to assist in preventing spread of agents that may be dispersed over long distances.
In contrast to tuberculosis, measles, and varicella, the pattern of disease spread for seasonal influenza does not suggest transmission across long distances (e.g., through ventilation systems); therefore, negative pressure rooms are not needed for patients with seasonal influenza (6, 8). However, localized airborne transmission may occur over short distances (i.e., three to six feet) via droplet nuclei or particles that are small enough to be inhaled. The relative contribution of short-range airborne transmission to influenza outbreaks is unknown.
Several often-cited papers raise concern about short-range aerosol transmission as a possible route of spread for influenza. These include laboratory studies in animals ( 3, 4, 5, 11), observational studies during the 1957-58 influenza pandemic (1), and an epidemiologic study of transmission on an airplane with an inoperative ventilation system (2). An experimental study in which the infectious dose of influenza virus was found to be as much as 100-fold lower for persons infected with small aerosols than with nasal drops (12) has further raised this concern. Although data are limited, the possibility remains that short-range aerosol transmission is a route of influenza transmission in humans and requires further study (13).
Aerosol-Generating Procedures
It is likely that some aerosol-generating medical procedures (e.g., endotracheal intubation, open suctioning, nebulizer treatment, bronchosocopy) could increase the potential for generation of small aerosols in the immediate vicinity of the patient. Although this mode of transmission has not been evaluated for influenza, given what is known about these procedures, additional precautions for health care personnel who perform aerosol-generating procedures on influenza patients are warranted.
Contact Transmission (Direct and via Fomites)
Contact transmission of influenza may occur through direct contact with contaminated hands, skin, or fomites followed by auto-inoculation of the respiratory mucosa. Influenza transmission via contaminated hands and fomites has been suggested as a contributing factor in some studies (14). There are insufficient data to determine the proportion of influenza transmission that is attributable to direct or indirect contact. However, it is prudent to reinforce recommendations for thorough and frequent handwashing, which is known to reduce the likelihood of contamination of the environment and to reduce transmission of respiratory infections (15, 16, 17). Surgical mask or respirator use may provide an additional benefit by discouraging facial contact and subsequent autoinoculation.
Pathogenesis of Influenza and Implications for Infection Control
Human influenza is a disease of the respiratory tract. Influenza virus infects respiratory epithelial cells via receptors found principally in non-ciliated cells of the upper respiratory tract; infection also can occur in the lower respiratory tract (18, 19). There is no natural or experimental evidence that human seasonal influenza virus infection of the gastrointestinal tract can occur. While conjunctivitis may be associated with human infection with some avian influenza viruses (20, 21), ocular infection does not appear to be a primary route for transmission of human influenza viruses, although data are very limited. Nonetheless, it is prudent to prevent exposure of the eyes as well as the mucous membranes of the respiratory tract to possibly infectious material (e.g., as may occur when health care workers perform splash-generating procedures).
Experience from Control of Seasonal Influenza Transmission
Outbreaks of seasonal influenza in hospitals and long-term care facilities have been prevented or controlled through a set of well-established strategies that include the following:
• seasonal influenza vaccination of patients and health care personnel
• early detection of influenza cases in a facility
• antiviral treatment of ill persons and prophylactic treatment of particularly susceptible persons
• implementation of the following administrative measures
- restricting visitors
- educating patients and staff
- cohorting health care personnel assigned to an outbreak unit
• isolation of infectious patients in private rooms or cohorted units
• practicing and emphasizing the importance of good hand hygiene
• use of appropriate barrier precautions (e.g., masks, gloves, and gowns) during patient care, as recommended for Standard and Droplet Precautions (8). Respirators have not been routinely recommended for control of seasonal influenza outbreaks.
Used together, these measures have been successful in controlling outbreaks of seasonal influenza in health care settings; however, the relative contributions of each of the interventions listed above remain unknown, and their specific impact during a pandemic is difficult to predict.
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Source: http://www.cdc.gov/travel/other/avian_influenza_se_asia_2005.htm
Accessed 5/17/07
Most recently updated: February 2, 2007 Initially released: September 23, 2005 |
Current Situation Phase 3 (Pandemic Alert).
CDC Recommendations
CDC has not recommended that the general public avoid travel to any of the countries affected by H5N1 viruses. Persons visiting H5N1-affected areas can reduce their risk of infection by observing the following measures.
Before travel to an area affected by H5N1 virus, follow these routine precautions
Visit CDC's Travelers’ Health Website to educate yourself and others who may be traveling with you about any disease risks and CDC health recommendations for international travel in areas you plan to visit.
Be sure you are up-to-date with all your routine vaccinations, including seasonal influenza vaccine, and see your doctor or health-care provider, ideally 4–6 weeks before travel, to get any additional vaccinations, medications or information you may need.
Assemble a travel health kit containing basic first aid and medical supplies. Be sure to include a thermometer and alcohol-based hand gel (containing at least 60% alcohol) for hand hygiene. See Travelers’ Health Kit in Health Information for International Travel for other suggested items.
Identify in-country health-care resources in advance of your trip.
Check your health insurance plan or get additional insurance that covers medical evacuation in case you become sick. Information about medical evacuation services is provided on the U.S. Department of State web page, Medical Information for Americans Traveling Abroad.
During travel to an H5N1-affected area:
Avoid all direct contact with birds, including domestic poultry (such as chickens and ducks) and wild birds.
Avoid places such as poultry farms and bird markets where live birds are raised or kept.
Avoid touching surfaces contaminated with poultry feces or secretions.
As with other infectious illnesses, one of the most important preventive practices is careful and frequent handwashing. Cleaning your hands often with soap and water removes potentially infectious material from your skin and helps prevent disease transmission. Waterless alcohol-based hand gels (containing at least 60% alcohol) may be used when soap is not available and hands are not visibly soiled.
During travel to an H5N1-affected area (continued):
All foods from poultry, including eggs and poultry blood, should be cooked thoroughly. Egg yolks should not be runny or liquid. Because influenza viruses are destroyed by heat, the cooking temperature for poultry meat should be 74°C (165°F).
If you become sick with symptoms such as a fever plus a cough, sore throat or have trouble breathing, or if you develop any illness that requires prompt medical attention, a U.S. consular officer can assist you in locating medical services and informing your family or friends. Inform the health-care provider of any possible exposures to avian influenza, such as exposures to ill or dead birds. See Seeking Health Care Abroad in Health Information for International Travel for more information about what to do if you become ill while abroad. You should defer further travel until you are free of symptoms, unless traveling locally for medical care.
To help stop the spread of germs,
Cover your mouth and nose with a tissue when you cough or sneeze.
If you don't have a tissue, cough or sneeze into your upper sleeve, not your hands.
Put your used tissue in the waste basket.
Clean your hands after coughing or sneezing by washing them with soap and water (or by using an alcohol-based hand cleaner with at least 60% alcohol when soap and water are not available).
You may be asked to put on a surgical mask to protect others.
Note: Some countries have instituted health monitoring techniques, such as temperature screenings, at ports of entry for travelers arriving from areas affected by the H5N1 virus. Please consult the embassy of your travel destination country if you have any questions.
After your return from an H5N1-affected area
Closely monitor your health for 10 days.
If you become ill with a fever plus a cough, sore throat or have trouble breathing during this 10-day period, consult a health-care provider. Before you visit a health-care setting, tell the provider the following: 1) your symptoms, 2) where you traveled, and 3) if you have had direct contact with poultry or close contact with a severely ill person. This way, he or she can be aware that you have traveled to an area reporting H5N1.
Do not travel while ill, unless you are seeking local medical care. Limiting contact with others as much as possible can help prevent the spread of an infectious illness.
Date: February 2, 2007 Content Source: National Center for Infectious Diseases, Division of Global Migration and Quarantine
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By Susan Allan, MD, JD, MPH, Health Director, Arlington, Virginia
The experiences of the communities that lived through severe acute respiratory syndrome (SARS) last year are instructive and sobering. The public health and other officials from the countries that were affected by SARS last year have been generous in sharing details of their experience and their lessons learned. I have had the opportunity to participate in several conferences and meetings with officials from Toronto, Singapore, Taiwan, and Hong Kong. From Toronto in particular, I have heard from and spoken with not only their public health officials, but also their legal counsel, chiefs of police for the city and for the province, and private emergency room and infectious disease physicians. A number of more extensive articles have recently been published regarding the range of legal and policy issues raised by the SARS experience; these articles are a valuable reference for anyone wanting to go deeper into these issues. In this brief article, I will attempt to summarize the major legal, policy, and resource issues that seem to have the greatest significance for local public health agencies. Because the social, legal, and health care systems of Toronto are most similar to those of the United States, I will draw most heavily from their experience.
The scale of the response to SARS in these affected countries was astounding, but one of the lessons learned is that they cannot provide firm information on numbers quarantined or isolated. For Taiwan, estimates have ranged from 80,000 to 130,000 people quarantined. Estimates for number quarantined in Toronto have ranged from 23,000 to 29,000 during the three months of the outbreak, with as many as 7,000 under quarantine at any one time. The total number of actual SARS cases in Toronto was 375, so the number of people quarantined was vastly greater than the number of people who ultimately became ill. Because the early experience with SARS in a hospital in Vietnam had suggested a possible fatality rate of 50 percent, these countries felt they needed to
take drastic measures initially, until later experience with the disease provided more information about modes of transmission and showed a lower, but still significant, fatality rate.
An important point to note is that the vast majority of both quarantined and isolated individuals complied voluntarily and were never taken through any kind of legal process or court order. They were given directives from their health department staff, private physician, in some cases from their employer (hospitals, for example), but were not actually issued a formal order of quarantine or isolation unless they were noncompliant.
The vast majority were compliant with instructions they were given—Toronto only issued 27 legal orders. They believe that they were able to achieve this high level of compliance with voluntary quarantine in large part because of the extensive efforts to ensure that the community at large understood what was needed and why, and also because of the very labor intensive monitoring and support systems they developed for those in quarantine. These included placing telephone calls to the individuals twice daily;
maintaining logs of symptoms (especially temperature and respiratory symptoms); ensuring that people had the supplies needed to remain in their homes, such as food and medications; providing someone to talk with about their fears and anxieties, etc. The logistical burden was extensive. They also set up a community hotline staffed by public health nurses, which fielded approximately 300,000 telephone calls in total. Although there are legal and epidemiologic distinctions between quarantine and isolation, for the most part the communities handled the logistics of quarantine and outpatient isolation very similarly. (Inpatient “isolation” was generally a matter of providing infection control while treating severely ill patients in a hospital setting, which presented medical treatment and hospital management challenges that will not be discussed further here.) Most often, they would "isolate" or "quarantine" people to their own homes, with instructions on how to keep separate from the rest of the household and how to maintain specific infection control practices. This made the quarantine or isolation much easier for the government to manage, since no separate facility needed to be maintained and the family could help provide much of the routine support, whether the individual was well or sick. People might be "quarantined," then become
moderately symptomatic and remain in the home, unless they actually needed to be hospitalized due to the severity of illness. In most of the affected communities, they did provide some sort of a facility for people who were "advised" to be quarantined but preferred not to stay at home and potentially put their families at risk.
Some current and proposed state laws in the U.S. describe different procedures for issuing quarantine orders and isolation orders. For small numbers of affected individuals, it may not be unduly burdensome to shift from a quarantine order to an isolation order for those who become ill while in quarantine. Quarantine laws are being drafted that more explicitly could apply quarantine to large groups of people, while isolation laws generally are crafted to apply only to specifically identified individuals. In a situation with thousands who need to be quarantined, it may be more practical to create a process to extend the quarantine order once someone becomes symptomatic without necessarily going through a second process to obtain an isolation order. On the other hand, requiring an individual hearing for isolation orders may be a practicable approach if the isolation order would be necessary only for those not voluntarily complying, which is likely to be a much smaller number. Because the period of isolation for someone who is ill could end up much longer than the quarantine period, it may be appropriate from a civil rights perspective to have a more individualized procedure for isolation orders.
When people have the right of appeal, or to have a hearing pertaining to a quarantine or isolation order, there may be a practical question of how to provide counsel to large numbers of people within the short timeframes that would be involved. Existing systems for appointing counsel may quickly be overwhelmed, or the laws may be written so that there is no right to have counsel provided in these circumstances.
Most existing laws do not address the issue of what to modify in terms of a quarantine or isolation order for a whole facility or group of people, e.g., when initially the whole hospital was quarantined, and later it is determined that the quarantine or isolation can be limited to the emergency room or the intensive care unit. Toronto developed the concept of “work quarantine”, which was applied to healthcare and EMS workers, in order to permit those systems to continue to operate while large numbers of their workers were in quarantine. At one point, Toronto had about 400 of the 875 paramedics operating under “work quarantine”—they were permitted to go to work, using appropriate PPE and other infection control precautions; and could drive straight home,
where they maintained appropriate distance and other separation measures from others in the household. But they were restricted from engaging in any other activities or going any place else. It is not clear whether a work quarantine option exists under the laws of most of the U.S. states.
During the SARS outbreak, Toronto passed several laws relating to employment rights and compensation. They passed legislation to protect employees who were home on voluntary quarantine or isolation from intimidation or dismissal by their employers. However, in some cases employers lost so much business during that period that they needed to lay off employees. Toronto also made provisions to compensate people for
lost wages or income due to quarantine or isolation. Because formal quarantine and isolation orders were issued so rarely, question arouse how to prove that an employee had been directed to stay away from work or that a business had been directed to close, rather than having made a personal decision to stay away from work due to fear of being infected by others. Toronto also passed laws prohibiting inappropriate discrimination by an employer or business based on a false belief that a person presented a risk to others.
Law enforcement agencies in Toronto and other affected communities faced a number of challenges. Typically, state and local laws require that someone from a branch of law enforcement serve notice of an individual order of quarantine or isolation. This can present a significant workload for a law enforcement department that is likely already to be stretched by responding to the public crisis. Law enforcement also assisted with monitoring those in quarantine who appeared to be noncompliant, and helped send a
message to the community that these orders were to taken seriously. In Toronto, there was one criminal investigation of an individual who infected a coworker with SARS when he failed to comply with a quarantine order. The prosecution was dropped because the index case subsequently died.
Legal and security issues arose regarding restricting visitors to patients who were in isolation or who were in the two quarantined hospitals. Some cases were quite tragic, when family members were not allowed to visit their sick or dying relatives. On some occasions, public health and law enforcement authorities prohibited certain kinds of public gatherings. For example, a public funeral was prohibited when some family members had been a source of infection to others while attending an earlier funeral of a family member and many members of the family were still in quarantine or isolation.
Certain church services were cancelled for a period of time when the church had previously been a site of disease transmission and members were being monitored for symptoms. Although the number of deaths did not turn out to be overwhelming, officials sought the authority to require cremation of bodies if needed, even if against the family’s wishes or religious beliefs.
To effectively use quarantine and isolation as tools to control a disease outbreak, it is essential that cases of diseases be reported promptly to public health authorities.Toronto officials are concerned that the existing requirements for physicians to report diseases and consequences for failure to report may not be strong enough for situations such as SARS, where identifying and managing every single case is critical. They do not
believe they have found a good answer to this problem. Poor reporting of diseases is already a concern of many local health departments in this country.
From this brief overview of some of the legal and policy issues related to quarantine, isolation and response to a disease outbreak, it is clear that such situations could present challenges for which many of our current laws, plans and resources are not adequate. The legal and public health authorities from Toronto have spoken out clearly and emphatically that the middle of an epidemic is not the best time to be rewriting laws and developing plans. We would do well to heed their message.
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