eMedicine Specialties > Infectious Diseases > Viral Infections
Influenza: Follow-up
Updated: Aug 12, 2009
Follow-up
Further Inpatient Care
- Hospitalization
- Most frequently, hospitalization is necessary when influenza exacerbates underlying chronic diseases. Some patients, especially elderly individuals, may be too weak to care for themselves alone at home.
- On occasion, the direct pathologic effects of influenza may require hospitalization. Most commonly, this is influenza pneumonia.
Further Outpatient Care
- Patients with influenza who do not improve should return for further evaluation. Patients diagnosed with influenza should be educated about potential complications and encouraged to return for evaluation if concerned. This is especially true of patients with underlying chronic disease or those who are immunocompromised.
Deterrence/Prevention
- Influenza vaccine provides good protection against immunized strains. The vaccination becomes effective 10-14 days after administration.
- Each year in the United States, a vaccine that contains antigens from the strains most likely to cause infection during the winter flu season is produced.
- As an historic example, during 2001-2003, 2 strains of influenza A virus (A/Panama/2007/99 [H3N2] and A/New Caledonia/20/99 [H1N1]) and 1 strain of influenza B (B/Hong Kong 330/01) comprised the vaccine.
- For the 2009-2010 season, the trivalent vaccine contains the following antigenic strains: A/Brisbane/59/2007 (H1N1)–like virus, A/Brisbane/10/2007 (H3N2)–like virus, and B/Brisbane/60/2008–like antigens (changed from B/Florida/4/2006–like virus in the 2008-2009 Northern Hemisphere influenza vaccine).9
- Influenza vaccine is also available as a nasal spray (FluMist) for healthy children aged 5 years or older, adolescents, and adults aged younger than 50 years. Clinical trials are limited in scope regarding the protective effects of live vaccine. The live virus is attenuated by cold; therefore, only very limited viral replication occurs at temperatures of more than 95°F.
- Specific recommendations for individuals who should be immunized can be obtained from the CDC (see Prevention and Control of Influenza). People recommended for immunization include elderly individuals, those with certain chronic diseases, and health care workers.
- In order to improve the immunogenicity of influenza virus vaccine in elderly adults, a high-dose trivalent inactivated influenza vaccine has been developed. In a multicenter, randomized, double-blind controlled trial, seroconversion of the high-dose vaccine was compared with seroconversion of the standard-dose vaccine in elderly adults (≥65 y). A statistically significant increase in seroconversion rate was found in those who received the high-dose vaccine (n=2575) compared with the standard-dose vaccine (n=1262). The high-dose vaccine met superiority criteria for both strains of influenza A, and noninferiority criteria were met for influenza B strains. Seroprotection rates were higher for the high-dose vaccine compared with the standard-dose vaccine. The authors suggest that the high-dose vaccine may provide improved immunity for elderly adults.10
- A vaccine designed to be effective against H5N1 is approved.
Complications
- Primary influenza pneumonia is characterized by progressive cough, dyspnea, and cyanosis following the initial presentation on the infection. Chest radiographs show diffuse infiltrative patterns bilaterally, without consolidation, which can progress to a presentation similar to acute respiratory distress syndrome. Risks for viral pneumonia involve numerous complex host immune responses and viral virulence. Although elderly individuals, especially nursing home patients, and those with cardiovascular disease constitute the highest risk groups, do not forget that, in the 1918-1919 epidemic, many young adults died of a pneumonia that some experts believe was caused directly by the virus.
- Secondary bacterial pneumonia can occur from numerous bacteria (eg, Staphylococcus aureus, Streptococcus pneumoniae, Haemophilus influenzae ).
- The most dreaded complication is staphylococcal pneumonia, which develops 2-3 days following the initial presentation of viral pneumonia. Patients appear severely ill, with hypoxemia, an elevated WBC count, productive bloody cough, and a chest radiograph showing multiple cavitary infiltrates. Methicillin-susceptible S aureus ( MSSA) and methicillin-resistant S aureus (MRSA) pneumonias have occurred following influenza pneumonia. MRSA pneumonia may be severe and difficult to treat, and deaths have occurred within 24 hours of presentation of pneumonia symptoms.
- S pneumoniae or H influenzae pneumonia, if occurring as a complication, usually develops 2-3 weeks after the initial symptoms of influenza and can be managed as a community-acquired pneumonia, following standard antibiotic and admission/discharge guidelines. Myositis is a rare complication. This group of patients may develop frank rhabdomyolysis, with elevated creatine kinase levels and myoglobinuria.
- Myocarditis and pericarditis have been associated with influenza infections.
Prognosis
- In patients without comorbid disease, the prognosis is very good, although some patients have a prolonged recovery time and remain weak and fatigued for weeks.
Patient Education
- For excellent patient education resources, visit eMedicine's Cold and Flu Center. Also, see eMedicine's patient education article Flu in Adults.
Miscellaneous
Medicolegal Pitfalls
- Early presentations of more serious infections may initially be misdiagnosed as influenza.
- Physicians who diagnose influenza in residents of nursing homes should notify the nursing home medical director so that preventive measures can be taken to protect other residents.
- Postinfluenza pneumonia is a serious complication and needs to be treated aggressively.
More on Influenza |
| Overview: Influenza |
| Differential Diagnoses & Workup: Influenza |
| Treatment & Medication: Influenza |
 Follow-up: Influenza |
| References |
| Further Reading |
| « Previous Page |
References
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Further Reading
Additional resources on influenza are available at Medscape's Influenza Resource Center.
Keywords
influenza, flu, influenza virus, flu virus, influenzavirus, influenza A, influenza B, influenza C, influenza A subtype H3N2, H1N1, H5N1, H9N2, avian influenza, avian flu, bird flu, upper respiratory tract infection, URTI, severe acute respiratory syndrome, SARS, flu pandemic, Orthomyxoviridae, respiratory syncytial virus, RSV, West Nile virus
