INFLUENZA

https://doi.org/10.1016/S0891-5520(05)70222-1Get rights and content

Influenza is an acute, febrile respiratory illness of global importance caused by serotypes A, B, and C of the influenza virus. In a typical season, the disease affects 5% to 40% of the population. In the United States, it is estimated that an average of approximately 110, 000 hospitalizations per year and 20, 000 deaths are related to complications of the illness. Elderly people, very young children, and patients with chronic cardiopulmonary conditions are at highest risk for developing influenza.74

Because of their ability to mutate and their potential to move from animal reservoirs to humans, influenza viruses are able to emerge or re-emerge as “new viruses” with the potential of spreading rapidly through susceptible populations and causing worldwide epidemics or pandemics of influenza.

The three most important pandemics caused by influenza viruses during the twentieth century were the pandemic of 1918 and 1919, with 2 billion people affected and 20 to 40 million deaths; the 1957 “Asian influenza” pandemic, and the 1968 pandemic of “Hong-Kong influenza.”22

The development of new therapeutic options for individuals with respiratory viral infections and the need to limit unnecessary antimicrobial use have resulted in the generation of new diagnostic tests for influenza. These methods range from classic tissue culture to modern molecular procedures.

Vaccination with the currently available trivalent inactivated influenza vaccine is the most effective preventive measure for reducing the impact of influenza during epidemics and pandemics of the disease. During recent years, some Latin American countries have carried out important programs and vaccination campaigns in the elderly and other high-risk groups. These efforts have allowed us to obtain estimates of vaccine effectiveness and the adverse effects of inactivated influenza vaccine, and they have proved to be useful in improving immunization coverage in these populations. The new live attenuated cold-adapted vaccines, which are delivered intranasally, may help to prevent the spread of the disease if they become available in the near future.11, 89

The current antiviral drugs (amantadine and rimantadine) may be used against influenza A infections. The advantages of the new neuraminidase inhibitors are their ability to stop viral replication in influenza A and B viruses, their usefulness in treating severe infection, and their potential to reduce the risk of complications.40, 41

The purpose of this article is to present summarized, categorized, and updated information on influenza. The authors hope that this knowledge will contribute to the prevention and adequate management of the disease.

Section snippets

EPIDEMIOLOGY OF INFLUENZA

Influenza viruses differ from many other viral respiratory pathogens because they cause both annual epidemics that affect all age groups and more serious pandemics (worldwide epidemics) that spread rapidly and pervasively through populations. During influenza epidemics and pandemics, a sharp rise in acute illness results in increased numbers of visits to physicians' offices, walk-in clinics, and emergency rooms. Increased hospitalizations for management of lower respiratory tract complications

LABORATORY DIAGNOSIS OF INFLUENZA

Laboratory identification is required for a definitive diagnosis of influenza and serves several purposes. If a laboratory confirmation of influenza is available early during the course of infection, the patient may benefit from specific antiviral treatment with amantadine, rimantadine, or one of the neuraminidase inhibitors that recently have become available in some countries.41, 49 Laboratory diagnosis of influenza virus infections is also the foundation of global influenza surveillance.

The

CLINICAL FEATURES

The spectrum of clinical presentations of influenza is extremely broad. During some epidemic seasons, the rate of asymptomatic infection may be as high as that of symptomatic infection. The severity of the illness is variable, ranging from mild rhinitis or pharyngitis to respiratory infections (primary viral or secondary bacterial pneumonia), multisystem complications, or death. Classic symptoms include high-grade fever, myalgia, chills, headaches, sore throat, dry cough, and malaise, with

INFLUENZA VACCINE

The composition of the currently inactivated vaccine includes a determined amount and type of antigen, usually two type A antigens (H1N1 and H3N2) and one type B antigen of influenza virus. Whole-virus, subvirion, and purified surface-antigen preparations are available for intramuscular administration.48 Currently available influenza purified vaccines are much less reactogenic than early formulations and are well tolerated, although systemic and local reactions can be observed.48, 74

There are

ANTIVIRALS

The two available antivirals are amantadine hydrochloride and rimantadine hydrochloride. These chemically related drugs block the replication cycle of influenza A virus. Amantadine and rimantadine proved to be effective in the treatment of healthy young adults with influenza when administered within 48 hours of illness onset. Both drugs can reduce severity and shorten the duration of disease, but their ability to prevent complications of influenza A has not been established.87

Rimantadine is

PLANNING FOR THE NEXT INFLUENZA PANDEMIC

Influenza pandemics are likely to be a relatively modern development, related to increases in global population and the growth of mass transportation systems necessary for the worldwide dissemination of the novel virus. Animals such as horses may have played a role in past influenza epidemics, and pigs and birds have been suggested to play key roles in generating viruses responsible for modern-day pandemics.90, 91 The three pandemics of the past century occurred unpredictably, at irregular

SUMMARY

Influenza is an acute respiratory illness of global importance that causes considerable morbidity and mortality every year. At the beginning of the millennium, influenza will still be an emergent or re-emergent infection because of the viral ability to mutate. Global influenza surveillance indicates that influenza viruses may vary within a country and between countries and continents during an influenza season. Virologic surveillance is of critical importance in monitoring antigenic shift and

References (97)

  • K.F. Shortridge

    The next pandemic influenza virus?

    Lancet

    (1995)
  • R.L. Tominack et al.

    Rimantadine hydrochloride and amantadine hydrochloride use in influenza A virus infections

    Infect Dis Clin North Am

    (1987)
  • R.G. Webster et al.

    Influenza—an emerging and re-emerging disease

    Seminars in Virology

    (1994)
  • K. Anderson et al.

    Improving Influenza Vaccination Coverage in the Medicare Population

  • F.Y. Aoki

    Amantadine and rimantadine

  • Arduino RC, Martin T, Bonvehí P, et al: Safety of inactivated subunit influenza virus vaccines (ISIVVs) combined with...
  • J. Aschan et al.

    Influenza B in transplant patients

    Scand J Infect Dis

    (1989)
  • M. Aymard et al.

    Recommendations of the 7th European Meeting of Influenza and Its Prevention

    Eur J Epidemiol

    (1994)
  • D. Bainton et al.

    Influenza and ischemic heart disease: A possible trigger for acute myocardial infarction?

    Int J Epidemiol

    (1978)
  • W.H. Baker et al.

    Pneumonia and influenza deaths during epidemics

    Arch Intern Med

    (1989)
  • W.H. Barker

    Excess pneumonia and influenza associated hospitalization during influenza epidemics in the United States, 1970–78

    Am J Public Health

    (1996)
  • E.D. Belay et al.

    Reye's syndrome in the United States from 1981 through 1997

    N Engl J Med

    (1999)
  • R.B. Belshe

    The efficacy of live attenuated, cold-adapted, trivalent, intranasal influenza virus vaccine in children

    N Engl J Med

    (1998)
  • R.F. Betts

    Influenza virus

  • P. Bisel et al.

    New approaches to vaccination

  • S.S. Bondarenko et al.

    The effect of influenza and parainfluenza on the course of ischemic heart disease

    Ter Arkh

    (1992)
  • Bonvehí PE, Nacinovich FM, Rüttimann RW, et al: Effectiveness of influenza vaccine in elderly people living in the...
  • D.P. Calfee et al.

    New approaches to influenza chemotherapy. Neuraminidase inhibitors

    Drugs

    (1998)
  • D.P. Calfee et al.

    Safety and efficacy of intravenous zanamivir in preventing experimental human influenza A virus infection

    Antimicrob Agents Chemother

    (1999)
  • F. Carrat et al.

    Evaluation of clinical case definitions of influenza: Detailed investigation of patients during the 1995–1996 epidemic in France

    Clin Infect Dis

    (1999)
  • S.D. Collins

    Age and sex incidence of influenza and pneumococcal morbidity and mortality in the epidemic of 1928–29 with comparative data for the epidemic of 1918–19

    Public Health Rep

    (1931)
  • F.M. Davenport et al.

    Epidemiologic and immunologic significance of age distribution of antibody to antigenic variants of influenza virus

    J Exp Med

    (1953)
  • R.C. Dykes et al.

    A clinical, epidemiologic, serologic, and virologic study of influenza C virus infection

    Arch Intern Med

    (1980)
  • F.A. Ennis et al.

    Antibody and cytotoxic T lymphocyte responses of humans to live and inactivated influenza vaccines

    J Gen Virol

    (1982)
  • D.A. Foster et al.

    Influenza vaccine effectiveness in preventing hospitalization for pneumonia in the elderly

    Am J Epidemiol

    (1992)
  • J.P. Fox et al.

    Influenza virus infections in Seattle families, 1975–79. I. Study design, methods and the occurrence of infections by time and age

    Am J Epidemiol

    (1982)
  • W.H. Frost

    The epidemiology of influenza

    JAMA

    (1919)
  • J.D. Fuller et al.

    Influenza vaccination of human immunodeficiency virus (HIV)-infected adults: Impact on plasma levels of HIV type 1 RNA and determinants of antibody response

    Clin Infect Dis

    (1999)
  • P. Gardner et al.

    Immunization in Adults in the 1990s

  • W.P. Glezen et al.

    Interpandemic influenza in the Houston area, 1974–76

    N Engl J Med

    (1978)
  • W.P. Glezen

    Emerging infections: Pandemic influenza

    Epidemiol Rev

    (1996)
  • W.P. Glezen

    Serious morbidity and mortality associated with influenza epidemics

    Epidemiol Rev

    (1982)
  • T.M. Govaert et al.

    Adverse reactions to influenza vaccine in elderly people: Randomized double blind placebo controlled trial

    BMJ

    (1993)
  • P.A. Gross

    The efficacy of influenza vaccine in elderly persons

    Ann Intern Med

    (1995)
  • A. Hampson et al.

    Global Surveillance for Pandemic Influenza: Are We Prepared?

  • Hayden FG, Lobo M, Treanor JJ, et al: Efficacy and tolerability of oral GS4104 for early treatment of experimental...
  • F.G. Hayden et al.

    Efficacy and safety of the neuraminidase inhibitor Zanamivir in the treatment of influenza virus infections

    N Engl J Med

    (1997)
  • N.L. Hordvik et al.

    Effects of acute viral respiratory tract infections in patients with cystic fibrosis

    Pediatr Pulmonol

    (1989)
  • Cited by (66)

    • Ultrasensitive detection of avian influenza A (H7N9) virus using surface-enhanced Raman scattering-based lateral flow immunoassay strips

      2019, Analytica Chimica Acta
      Citation Excerpt :

      The ability for prompt detection of these viruses is of the utmost importance in protecting both public health and the poultry economy. Virus isolation in embryonated chicken eggs (ECEs) is considered the gold standard for AIV detection, but complex procedures are time consuming [34]. Real-time polymerase chain reaction (RT-PCR) is a highly sensitive and fast method in virological monitoring, but high levels of amplification usually results in possible false positives [35].

    View all citing articles on Scopus

    Address reprint requests to Daniel Stamboulian, MD, Fundación del Centro de Estudios Infectológicos (FUNCEI), French 3085, 1425, Buenos Aires, Argentina, [email protected]

    View full text