Prevención primaria

In non-healthcare settings, recommendations for the public are similar to those for controlling the spread of seasonal influenza. [26] These recommendations include:

• Frequent hand washing; avoid touching eyes, nose, and mouth [27]

• Remaining at a distance of at least 1.8 metres (6 feet) from those with suspected illness. Studies on influenza transmission suggest that viable virions can travel more than the '1 metre' distance recommended by the WHO

• If infected, staying at home for 24 hours after the fever has gone (without the use of antipyretics) except to seek medical care or obtain necessities

• Covering mouth and nose when sneezing or coughing.

In addition, those at high risk (e.g., patients with chronic medical or immunocompromising conditions, pregnant women, and children <5 years of age) should avoid large social gatherings, particularly where the pandemic H1N1 strain is known to be circulating in the community. Workers with symptoms should be encouraged to stay at home.

Routine use of face masks among the general public is not recommended. The effectiveness of this practice for prevention of influenza in the community is unknown. However, face masks may be considered for high-risk people who cannot avoid being the main caregiver to a patient with an influenza-like illness or who must work or interact with people with influenza-like illnesses. A randomised trial conducted among households in Hong Kong demonstrated that early use of hand hygiene and face masks by household contacts of patients with influenza (i.e., within 36 hours of symptom onset in the index patient) was associated with a significant reduction in secondary transmission. [28] A recent trial of Canadian nurses randomised to either a surgical masks or a N95 respirator when caring for patients with febrile respiratory illness (not necessary influenza) suggested that surgical masks were equivalent to N95 respirators in terms of protection. [29] Also, those with an influenza-like illness or confirmed influenza infection should wear a face mask around others if tolerable, particularly if still coughing or sneezing. Women who are breastfeeding and who have a confirmed or suspected influenza illness should also wear a face mask while breastfeeding if symptomatic. If the mother is too ill to breastfeed, the breast milk should be expressed if possible (e.g., by pump) and fed to the infant by bottle by a healthy caregiver. All respiratory and bodily fluids (e.g., sputum, diarrhoea) should be regarded as infectious.

Among healthcare institutions, resources and facilities vary widely, and each healthcare setting must tailor infection control practices accordingly. [CDC: Infection control in health care facilities] When feasible, patients presenting with an influenza-like illness should be isolated from other patients. Hospitalised patients with fever should be placed in respiratory isolation for 7 days or for 24 hours after the fever has resolved without the use of antipyretics (whichever is longer), since patients with illness severe enough to warrant hospitalisation may shed virus for a longer period of time. If respiratory isolation rooms are in short supply, priority should be given to patients earlier in the course of illness or with more severe illness, as they may be shedding virus at higher rates. However, patients may be discharged from the hospital when clinically appropriate, regardless of whether or not they were still in respiratory isolation while in the hospital.

If ill patients must be transported through public settings, they should wear a surgical mask and observe proper hand hygiene and cough etiquette (e.g., covering mouth with a tissue while coughing). Patients undergoing interventions or procedures likely to generate a significant amount of aerosols (e.g., intubation, bronchoscopy, nebuliser therapy) should ideally be kept in airborne infection isolation rooms with negative-pressure air handling at a minimum of 6 air exchanges per hour. At a minimum, patients should be admitted to the hospital in private rooms with the door closed at all times. Healthcare personnel entering the room should observe contact protection (by wearing disposable gown and gloves), respiratory protection (minimum protection: a N95 respirator that has been fit-tested), and eye protection. One study of healthcare workers, however, reported that surgical masks were not inferior to N95 respirators in terms of protection during the 2008 to 2009 influenza season, [29] suggesting that surgical masks may still be effective in the event of a shortage of N95 respirators. Visitors should also be encouraged to wear gown, gloves, N95 mask, and eye protection. [30] In the outpatient setting, physicians and healthcare workers should at least wear a surgical mask when seeing patients with influenza-like illness, in addition to observing good hand hygiene and wearing gloves if in contact with any potentially infectious body fluids.

Healthcare workers who develop fever and respiratory symptoms should stay home for 24 hours after resolution of fever, without the use of antipyretics. If caring for an immunocompromised patient population, healthcare workers with respiratory symptoms and fever should consider staying at home or temporary reassignment for 7 days after onset or 24 hours after resolution of fever (whichever is longer), unless influenza infection of respiratory secretions can be definitely ruled out (e.g., by real-time reverse transcriptase-PCR). [CDC: Prevention strategies for seasonal and influenza A(H3N2)v in health care settings] It is highly recommended that all healthcare personnel be immunised against both seasonal and H1N1 variant influenza viruses. [31]

Vaccines against the pandemic strain of swine influenza were made available during the pandemic, including both an inactivated influenza injectable vaccine ('flu shot') and a live attenuated nasal spray vaccine. [32] Numerous studies indicate that vaccination is both safe and efficacious. [33] [34] [35] Coverage of the pandemic strain of swine influenza is now being included in the seasonal influenza vaccination in the forms of a trivalent inactivated vaccine and a trivalent live attenuated influenza vaccine. [30] The US Centers for Disease Control and Prevention (CDC) recently expanded its recommendation for vaccination to include all persons over the age of 6 months. This recommendation is based on data from epidemiological studies conducted during the 2009 influenza A (H1N1) pandemic, which showed that the risk for influenza complications in persons aged younger than 50 years was greater than is typically seen for seasonal influenza. [36] In addition, pandemic influenza is expected to continue to circulate during the coming seasons and a substantial proportion of young adults do not yet have immunity as a result of natural infection with the virus. However, in case of limited vaccine supply, efforts should continue to focus on delivering vaccination to at-risk individuals. This includes but is not limited to: [36]

• Children >6 to 59 months

• People 50 years and older

• People with chronic pulmonary, cardiovascular (except hypertension), renal, hepatic, neurological, haematological, or metabolic disorders (including diabetes mellitus)

• People who are immunosuppressed

• Pregnant women

• People who are morbidly obese with BMI of ≥40

• Healthcare personnel

• American Indians/Alaska Natives

• Residents of nursing homes and other chronic-care facilities.

Of note, pregnancy is not a contraindication to vaccination and the American College of Obstetricians and Gynecologists also recommend routine vaccination of pregnant women. [37]

Because of the concern of secondary bacterial pneumonia among patients with influenza infection, it is recommended that health professionals ensure that all people >64 years of age and all high-risk patients (including those with diabetes and chronic lung disease) are current with the 23-valent pneumococcal polysaccharide immunisation. In addition, people who smoke are considered to be at risk and should also be immunised. The pneumococcal polysaccharide vaccine has not been clearly demonstrated to reduce the risk of pneumonia, but its use is based upon expert consensus. [38] The effect of pneumococcal immunisation on preventing post-influenza pneumococcal pneumonia is unclear. Children under the age of 5 years should be immunised with the 7-valent pneumococcal conjugate vaccine. [39]

Prophylaxis with antiviral agents is not generally recommended for otherwise healthy adults in low-risk categories. [32] If preventive treatment is necessary, oseltamivir or zanamivir can be given for 10 days after the last known exposure. Infants (<1 year of age) are at increased risk for complications, and clinical judgement must weigh the potential unknown risks of oseltamivir in infants against the possibility of their developing severe illness. If chemoprophylaxis therapy is given, oseltamivir should be used. It is not recommended in infants <3 months old unless the situation is judged to be critical, because of the lack of data in this age group.

HIV-positive patients who have been exposed to a person with an influenza-like illness or with probable or confirmed influenza should receive antiviral prophylaxis.

Post-exposure antiviral prophylaxis can also be considered for pregnant women who are close contacts of people with suspected or confirmed H1N1 swine influenza. The drug of choice is usually zanamivir because of its limited systemic absorption, but for women with respiratory disease or at risk of respiratory complications, oseltamivir can be used. Recommended duration of chemoprophylaxis is 10 days after the last known exposure. [40]