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The H1N1 Influenza Pandemic: Strategies for Controlling Its Spread


Before considering the infection control strategies recommended during the current H1N1 influenza pandemic, it is useful to review the transmission characteristics of influenza viruses-including H1N1-that form the basis for these strategies:

Before considering the infection control strategies recommended during the current H1N1 influenza pandemic, it is useful to review the transmission characteristics of influenza viruses-including H1N1-that form the basis for these strategies:

•Spread of infection tends to occur via large-droplet transmission.
•Once expelled into the air, large droplets tend to travel less than 6 feet before they fall to the ground.
•Viral particles may persist on nonporous surfaces and may be transferable to hands for variable periods of time.
•Aerosolization of the virus may occur during certain procedures-eg, bronchoscopy, intubation.
•Overall, airborne transmission (by generation of small-droplet nuclei)-such as is seen in tuberculosis, varicella, and measles-is not considered a major route of transmission for influenza viruses; more research is needed to determine the significance of airborne transmission over short distances in the health care setting.
•People tend to sneeze or cough into their hands and may transmit the virus to others if, in the interim, they do not practice effective hand hygiene to reduce the viral burden on their hands.
•Soap and water, as well as alcohol-based hand rubs, are very effective, especially when they are used appropriately (with soap and water, cleaning all surfaces of the hands and for sufficient time-30 seconds minimum; with gels, rubbing until the hands are dry). It is prudent for health care workers to practice hand hygiene as often as possible throughout the day, and certainly before every patient encounter. Several studies support this best practice.1,2
•Infected persons may be contagious from 1 day before the onset of symptoms until the time when symptoms resolve.


Current guidelines seem to recommend an overall more cautious approach with H1N1 than with seasonal influenza, primarily because it is too early to tell definitively whether novel H1N1 influenza viruses possess the same transmission characteristics as seasonal influenza. Measures that are recommended in health care settings include Standard and Contact Precautions (gown, gloves, eye protection, and masks). The specifics of the CDC guidelines for control of H1N1 infection, which are continuously updated, are available at http://www.cdc.gov/h1n1flu/guidelines_infection_ control.htm.

Masks and eye protection. According to the CDC, the preferred mask in the health care setting is a fit-tested, disposable N-95 respirator, which should be donned on entering a room. N95 respirators filter out at least 95% of particles (measuring 0.3 mm or larger), including those slightly smaller than the influenza virus itself. Even though surgical masks are considered the appropriate respiratory device to be worn on the face in the context of seasonal influenza (with H1N1 influenza presumed to have a similar transmission pattern), the N-95 mask is recommended for use in health care settings in the current outbreak largely because the extent of airborne transmission of H1N1 is unknown and more research needs to be done. This approach is supported by the CDC and a recent Institute of Medicine report.3 However, complete consensus regarding which type of respiratory device is recommended (surgical mask or N95 respirator) is still lacking, with the guidelines of other groups (such as the World Health Organization, Society for Healthcare Epidemiology of America, and Infectious Disease Society of America) being somewhat less stringent concerning respirators.4,5

N95 devices are, nonetheless, clearly recommended in settings in which aerosol-generating procedures are being performed. N-95 masks are disposable but can be reused repeatedly over 12 hours-‘however, only if all of the following criteria are met:

•Only 1 health care worker (HCW) uses the mask for only 1 patient (not for several).
•The mask is stored neatly in a clean, dry area if doffed during the period of use.
•The mask is kept free of dirt and humidity.

Patients who are likely to or definitely have H1N1 influenza should be asked to wear a surgical mask when they are coughing or sneezing and around other people. This is especially important in crowded areas, such as waiting rooms, and during clinic or hospital transport. Meticulous attention must be paid to patient flow in waiting rooms, clinic rooms, and procedure rooms or suites. Office staff in ambulatory care settings should also be afforded protection.

Surgical masks should be routinely used to protect patients and health care workers and prevent
droplet transmission in the context of clinical care. If "triage rooms“ or de facto "isolation rooms“ can be set up, the use of N-95 respirators may be integrated into clinical care. Guidance is available to help clinicians with infection control issues that arise in this setting.6 A tabular summary of facemask and respirator use is available on the CDC Web site (http://www.cdc.gov/h1n1flu/ masks.htm); it provides interim recommendations for non-ill persons in the home, community, and occupational settings.

Eye protection devices (goggles or face shields) should be used to protect workers from droplet transmission, especially in the context of splashing, aerosol-generating procedures.

Donning and doffing. Use of a protocol for donning and doffing can encourage consistent and efficient infection control practices (Guidance is available at http://www.cdc.gov/sars/downloads/ppeposter1322.pdf) In general, it is advisable to follow these principles:

•Remember not to touch contaminated surfaces-including gowns, eyewear, and masks-with bare hands.
•Don all personal protective equipment (PPE) before entering a room and doff all PPE before exiting the room.
•Even if you wear gloves, it is important to practice hand hygiene after doffing the gloves. Avoid putting on a mask once your hands (gloved or not) are contaminated.
•Ensure that once the PPE is donned, bare skin surfaces or personal devices (such as pagers) do not touch surfaces that may have been contaminated by respiratory or GI secretions.

Isolation. A clinician who cares for persons at risk for H1N1 influenza may wish to encourage his or her patients to call first rather than just show up at the clinic, office, or health care facility. If such phone triage can be implemented, then medication can either be called in (if warranted) or withheld (if not indicated). This approach would minimize exposure of HCWs and other uninfected patients to H1N1 virus.

If patients do enter a health care facility with symptoms of respiratory illness, it is advisable that some formal mechanism be in place to ensure reasonable sequestration of potentially contagious persons while they wait to be clinically evaluated. Also, encourage infected patients to cough or sneeze into the sleeve and not the hands, and remind them to immediately dispose of any contaminated tissue in an appropriate container.

If a patient with suspected/confirmed H1N1 influenza is isolated in a hospital setting, then a negative air pressure room is most appropriate. Ensure that there are the standard 6 to 12 air exchanges per hour and that negative air pressure is maintained.

An HCW who is experiencing an influenza-like illness (ILI) should ideally stay home. If an HCW who is critical to workforce needs is exposed to H1N1 but is asymptomatic, then it is recommended that the worker take all preventive measures to avoid transmission and scrupulously monitor temperature and symptoms. As soon as an ILI clinical picture develops, the HCW should go home and stay home for at least 7 days or until 24 hours after the resolution of symptoms.

Encourage commonsense measures as much as possible. For example, even though there is no prescribed restriction, limit visitors to the room of a patient infected with H1N1 virus to those closest to the patient, rather than permitting everyone in his family and circle of friends to visit. Also, it is most important to encourage everyone to practice good hand hygiene.

Inform patients and parents of specific danger signs to watch for in their loved ones, especially if these persons have suspected or confirmed H1N1 infection and have been advised to stay at home. These signs are listed in full on the CDC Web site (http://www.cdc.gov/h1n1flu/ guidance_homecare_directions.htm).7 Some ominous signs warranting emergent care include (for children) tachypnea, dyspnea, cyanosis, poor intake of fluids and dehydration, severe or persistent vomiting, somnolence and blunted interactivity, irritability, and flu-like symptoms that improve but then return with fever and worse cough. Emergency warnings signs in adults include dyspnea, chest or abdominal pain, dizziness, syncope, delirium, vomiting, and relapse of
worsened fever and cough after initial recovery.


Clinicians have unique roles in the public health and community responses to the current and future epidemics of influenza (H1N1, seasonal influenza, or illnesses caused by other pathogens). First, they can protect and preserve the health of their patients. Second, by remaining vigilant to unusual clusters of illness and adhering to guidelines for testing and reporting any notifiable disease to local public health authorities, they can enhance public health surveillance efforts.8

Health care providers, as well as the general public, should remain aware that despite what may be said in the general media, continued vigilance is required to assess important trends during the course of the current pandemic. Generally, the course of influenza illness and specifically H1N1 influenza in populations is unpredictable. Although unlikely, there is an ominous possibility that H1N1 influenza may mirror the epidemic of 1918, in which the first wave of illness in the spring of 1918 was followed by devastating second and third waves in the fall and winter of 1918-1919.

Third, because they are on the front line in dealing with infected and at-risk patients in their communities, clinicians can facilitate the effective communication of risk and public health messages to the media. Fourth, they can serve as information and education resources for businesses and other organizations.

Finally, it is critical that clinicians and other members of the health care team help public health officials reinforce preventive measures as often as possible. Remind patients, family members, and members of the public about the need to practice home isolation (ie, to stay home when ill); to cover their mouth and nose with a mask or handkerchief if they are ill and must be out in public; to cough or sneeze into their sleeve or elbow; to wash their hands frequently (and even carry alcohol-based hand gel on their person for ready use); to avoid touching their eyes, nose, and mouth; and to remain alert to their immediate environment-to avoid people who may be ill and symptomatic.


REFERENCES:1. Boyce JM, Pittet D; Healthcare Infection Control Practices Advisory Committee; HICPAC/SHEA/ APIC/IDSA Hand Hygiene Task Force. Guideline for Hand Hygiene in Health-Care Settings. Recommendations of the Healthcare Infection Control Practices Advisory Committee and the HICPAC/ SHEA/APIC/IDSA Hand Hygiene Task Force. Society for Healthcare Epidemiology of America/Association for Professionals in Infection Control/Infectious Diseases Society of America. MMWR Recomm Rep. 2002;51(RR-16):1-45.
2. World Health Organization. WHO guidelines on hand hygiene in health care. First global patient safety challenge: clean care is safer care. 2009. http://whqlibdoc.who.int/publications/2009/9789241597906_eng.pdf. Accessed August 25, 2009.
3. Institute of Medicine. Respiratory Protection for Healthcare Workers in the Workplace Against Novel H1N1 Influenza A. http://www.iom.edu/CMS/3740/71769/72967.aspx. Accessed September 8, 2009.
4. Infectious Disease Society of America. SHEA, IDSA stress basic infection control in protecting HCWs from novel H1N1. IDSA News. 2009;19(8). http://news.idsociety.org/idsa/issues/2009-08-01/8.html. Accessed September 24, 2009.
5. World Health Organization. Infection prevention and control in health care for confirmed or suspected cases of pandemic (H1N1) 2009 and influenza-like illnesses. Interim Guidance. June 25, 2009. http://www.who.int/csr/resources/publications/SwineInfluenza_infectioncontrol.pdf. Accessed September 24, 2009.
6. Public Health Agency of Canada. Interim guidance for clinicians in ambulatory care settings: human cases of swine influenza A (H1N1). http://www.phac-aspc.gc.ca/alert-alerte/swine-porcine/pdf/interim_guidance_for_clinicians_amb-eng.pdf. Accessed August 25, 2009.
7. Centers for Disease Control and Prevention. Home care guidance: physician directions to patient/parent. http://www.cdc.gov/h1n1flu/guidance_homecare_directions.htm. Accessed September 8, 2009.
8. National Notifiable Diseases Surveillance System. http://cdc.gov/ncphi/disss/nndss/nndsshis.htm. Accessed August 25, 2009.


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