Influenza (Flu)

Table of Contents

  1. Overview
  2. Virology & Strain Classification
  3. Transmission & Epidemiology
  4. Symptoms & Clinical Course
  5. Diagnosis
  6. Treatment & Antivirals
  7. Home & Supportive Care
  8. Complications & High-Risk Groups
  9. Prevention & Vaccination
  10. Pandemic Influenza
  11. Key Research Papers
  12. Connections
  13. Featured Videos

Overview

Influenza is an acute respiratory illness caused by influenza A, B, or C viruses belonging to the family Orthomyxoviridae. It is one of the most significant infectious diseases globally, responsible for an estimated 290,000–650,000 respiratory deaths per year worldwide according to the World Health Organization. In the United States alone, the CDC estimates 9–45 million illnesses, 140,000–810,000 hospitalizations, and 12,000–52,000 deaths each year depending on the dominant circulating strain and how well the seasonal vaccine matches it. Annual epidemics occur during winter months in temperate climates, peaking December through February in the northern hemisphere.

True influenza is distinct from the colloquial use of "flu" or "stomach flu" applied to any viral illness causing malaise. Clinically, influenza is defined by its abrupt, rapid onset — symptoms can progress from feeling well to severely ill within a matter of hours — combined with high fever, profound myalgias, and respiratory involvement. This distinguishes it from the common cold, which develops gradually and features predominantly nasal symptoms without the systemic collapse that influenza produces. Understanding this distinction is clinically important because influenza has a higher rate of serious complications and is amenable to antiviral treatment if started early.

Three main types of influenza infect humans. Influenza A is the most clinically significant, possessing pandemic potential due to its multiple animal reservoirs (birds, swine, horses, bats) and extensive subtype diversity classified by hemagglutinin (H1–H18) and neuraminidase (N1–N11) surface proteins. Currently circulating human strains are A(H1N1)pdm09 and A(H3N2). Influenza B infects humans and seals only, circulates in two lineages (Victoria and Yamagata), causes illness less severe than A on average, and has no pandemic potential due to its limited host range. Influenza C causes mild, sporadic illness predominantly in children, is not included in seasonal vaccines, and rarely produces significant outbreaks.

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Virology & Strain Classification

Influenza A and B viruses are enveloped, segmented, negative-sense single-stranded RNA viruses. Their genome consists of eight RNA segments encoding eleven proteins. This segmented architecture is the key structural feature enabling antigenic shift — the process by which two different influenza A strains co-infecting a single cell can swap entire RNA segments, potentially creating a novel reassortant virus with a new combination of surface antigens. Influenza C has seven segments instead of eight.

Two surface glycoproteins dominate influenza biology and vaccine design. Hemagglutinin (HA) is the attachment protein: it binds to sialic acid receptors on the surface of respiratory epithelial cells to mediate viral entry via receptor-mediated endocytosis. HA is the primary target of neutralizing antibodies generated by infection and vaccination; antibodies against HA block receptor binding and prevent infection. Human influenza A viruses preferentially bind alpha-2,6-linked sialic acid receptors, which predominate in the upper respiratory tract. Avian strains bind alpha-2,3-linked receptors abundant in the lower respiratory tract and avian intestinal epithelium — this receptor specificity is a key barrier to avian-to-human transmission. Neuraminidase (NA) is the enzyme that cleaves sialic acid bonds to release newly formed virions from infected cells and facilitate spread through mucus. NA is the target of oseltamivir, zanamivir, and peramivir (neuraminidase inhibitors), which trap viral particles on the cell surface and in mucus, preventing their release and further infection of neighboring cells.

Two mechanisms drive influenza's perpetual evolutionary challenge. Antigenic drift refers to the gradual accumulation of point mutations in the genes encoding HA and NA, driven by immune selection pressure. As mutations accumulate, the virus's surface antigens change enough that previously acquired immunity (from infection or vaccination) no longer provides complete protection against the drifted strain. This is the primary reason annual influenza vaccination is required — the vaccine must be updated each year to match the antigenically drifted strains predicted to circulate. The WHO coordinates a global surveillance network to select the strains for each hemisphere's vaccine formulation. Antigenic shift is the sudden, dramatic change in viral surface antigens that occurs through reassortment of RNA segments between two different influenza A subtypes co-infecting the same host cell. When a novel HA or HA/NA combination emerges to which the human population has little or no pre-existing immunity, pandemic conditions can arise.

Additional proteins of clinical relevance include the M2 ion channel, targeted by the adamantane class of antivirals (amantadine, rimantadine). However, nearly universal resistance to adamantanes has developed in circulating influenza A strains, rendering this class obsolete for treatment. The polymerase complex (subunits PB2, PB1, PA) is the target of baloxavir marboxil, which inhibits cap-dependent endonuclease activity — a mechanism distinct from neuraminidase inhibitors, making baloxavir active against oseltamivir-resistant strains.

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Transmission & Epidemiology

Influenza spreads primarily through respiratory droplets (particles >5 µm in diameter) expelled during coughing, sneezing, or talking, which can travel approximately 1–2 meters before settling. These droplets deposit on the mucous membranes of susceptible individuals in close proximity. A second transmission route — airborne transmission via fine aerosols (<5 µm) — remains the subject of ongoing scientific debate, but accumulating evidence from hospital outbreaks, choir rehearsals, and aircraft studies supports meaningful aerosol transmission in enclosed, poorly ventilated spaces. This distinction has significant implications for infection control recommendations. Fomite transmission — touching a contaminated surface and then touching the face — plays a secondary role; influenza virus remains viable on hard nonporous surfaces for up to 24 hours and on hands for approximately 5 minutes, supporting the importance of hand hygiene.

The incubation period is 1–4 days, with a mean of approximately 2 days from exposure to symptom onset. The contagious period begins approximately one day before symptom onset and extends 5–7 days after the onset of illness in otherwise healthy adults. Children shed virus for longer periods — often 10 or more days — and immunocompromised individuals may shed viable virus for weeks to months, sometimes harboring strains that accumulate resistance mutations during prolonged oseltamivir prophylaxis. This pre-symptomatic contagiousness is a key driver of community spread, as infected individuals are unknowingly transmitting the virus during the day before they feel ill.

Seasonal patterns are well established in temperate climates: influenza activity peaks December through February in the northern hemisphere, June through August in the southern hemisphere, and occurs year-round in tropical and subtropical regions with less pronounced seasonal peaks. Multiple factors contribute to winter seasonality, including reduced UV radiation (less viral inactivation), lower humidity (aerosol persistence increased, mucociliary clearance impaired), behavioral factors (more indoor crowding), and possible host factors related to vitamin D levels and mucosal immune function. The basic reproduction number (R₀) for seasonal influenza is approximately 1.2–1.4, meaning each case generates on average 1.2–1.4 secondary cases in a fully susceptible population — relatively modest but sufficient for epidemic spread. Pandemic strains have achieved R₀ values of 2–3.

Influenza A(H3N2) seasons are consistently associated with greater severity — more hospitalizations, more deaths, especially in elderly populations — compared with A(H1N1)pdm09 or B-dominant seasons. This reflects both the greater antigen mismatch H3N2 strains produce with egg-adapted vaccine antigens and the greater immune senescence-related vulnerability of older adults to H3N2.

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Symptoms & Clinical Course

The hallmark of influenza that distinguishes it from most other respiratory viruses is its abrupt onset. Whereas rhinovirus (common cold) symptoms develop gradually over 1–2 days, influenza characteristically strikes within hours — patients often describe being well in the morning and severely ill by evening. This rapid deterioration reflects the high viral replication kinetics and robust early innate immune response (interferon and cytokine surge) that influenza provokes.

Classic presentation in otherwise healthy adults:

Age-specific presentations vary significantly. In children, high fevers (which can reach 41°C) are more pronounced and febrile seizures are a recognized complication. Vomiting and diarrhea are more prominent in pediatric influenza than in adults — the "stomach flu" label is more appropriately applied to childhood influenza than to adult presentations. Otitis media is a frequent complication in young children. In elderly adults, the classic febrile presentation may be absent entirely; instead, influenza may present as new-onset confusion, falls, decompensation of underlying heart failure or COPD, anorexia, or generalized decline without prominent systemic symptoms. This atypical presentation frequently causes delay in diagnosis and treatment in the very population at highest risk for fatal outcomes. In pregnant women, dyspnea and hypoxemia can develop rapidly due to physiological changes in respiratory mechanics.

The clinical timeline in uncomplicated influenza: acute systemic symptoms (fever, myalgias, headache) peak days 2–3 and resolve by days 4–7; respiratory symptoms (cough, congestion) persist longer; fatigue often outlasts all other symptoms by 1–2 weeks. A practical rule of thumb: if an illness is severe enough to keep a person in bed, it is more likely influenza than a common cold.

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Diagnosis

Influenza diagnosis can be approached clinically or with laboratory confirmation, depending on the clinical context, resource availability, and the consequence of the result for management. During peak influenza season when community activity is high, the clinical diagnosis of a typical presentation (abrupt onset, high fever, myalgias, dry cough) has a positive predictive value of approximately 70–85%, making empiric antiviral treatment reasonable without confirmatory testing in otherwise healthy patients. However, laboratory confirmation is preferred for hospitalized patients, immunocompromised individuals, atypical presentations, and outbreak investigations.

Rapid Influenza Diagnostic Tests (RIDTs) detect influenza antigen by immunoassay from a nasopharyngeal or nasal swab; results are available within 15 minutes, making them highly practical in outpatient and emergency settings. The major limitation of RIDTs is their modest sensitivity of 50–70% — meaning a negative RIDT result does NOT reliably exclude influenza, particularly in adults (who shed lower viral loads than children) and in patients presenting beyond 48–72 hours of illness onset when viral titers are declining. Specificity exceeds 95%, so a positive RIDT in an epidemic period carries high positive predictive value and should prompt antiviral treatment. Sensitivity varies by specific test product and strain — H3N2 strains are detected less reliably than H1N1 by some RIDT platforms. Clinicians should not withhold treatment from high-risk patients with negative RIDTs if the clinical presentation is consistent with influenza.

Reverse transcription PCR (RT-PCR) is the gold standard for influenza detection, with sensitivity exceeding 95% and high specificity. RT-PCR not only detects influenza but identifies the type (A or B), subtype (H1N1 vs H3N2), and lineage (Victoria vs Yamagata for influenza B) — critical for surveillance, antiviral resistance monitoring, and tracking potential novel strains. Standard laboratory turnaround is 2–6 hours, though some platforms offer results in 60–90 minutes. Preferred for all hospitalized patients, immunocompromised individuals, and any case where the result will guide infection control decisions.

Multiplex PCR respiratory panels (e.g., BioFire FilmArray Respiratory Panel, Genmark ePlex) simultaneously detect influenza A, influenza B, RSV, SARS-CoV-2, human metapneumovirus, parainfluenza viruses, and 15+ additional respiratory pathogens from a single nasopharyngeal swab, with results in approximately 45 minutes. These panels are increasingly used in emergency departments and for hospitalized patients to guide isolation precautions and targeted treatment when the clinical picture is unclear. Their comprehensive pathogen coverage is particularly valuable in distinguishing influenza from SARS-CoV-2, which can present identically.

Direct fluorescent antibody (DFA) testing offers sensitivity of 70–80% and requires trained laboratory personnel; it remains in use at some reference laboratories. Viral culture is the historical gold standard but requires days to weeks for results — it is used for surveillance purposes, strain characterization, and antiviral susceptibility testing, not clinical management. Serology (demonstrating a 4-fold rise in hemagglutination-inhibition titer between acute and convalescent specimens) is a retrospective research and epidemiologic tool, not a tool for guiding individual patient treatment.

Specimen collection technique significantly affects test sensitivity. Nasopharyngeal swabs (posterior nasopharynx) provide higher viral yield than anterior nasal swabs in adults. Nasopharyngeal aspirates are preferred in young children. Timing matters: viral load peaks early in illness and declines substantially after day 4–5 in immunocompetent adults.

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Treatment & Antivirals

Antiviral treatment of influenza is most beneficial when initiated within 48 hours of symptom onset, when viral replication is most active. However, in hospitalized patients, severely ill individuals, and immunocompromised patients, antiviral therapy provides meaningful benefit even when started beyond 48 hours — including reduction in ICU admission, mechanical ventilation requirements, and mortality. Clinicians should not withhold antivirals from high-risk patients based on time-since-onset alone.

Neuraminidase Inhibitors — First-Line Agents:

Cap-Dependent Endonuclease Inhibitor — Newer Agent:

Adamantanes — NOT Recommended: Amantadine and rimantadine block the M2 ion channel of influenza A (no activity against influenza B). Adamantane resistance is now essentially universal in currently circulating influenza A strains due to decades of widespread use, particularly in China. These agents should not be used for influenza treatment or prophylaxis.

Post-Exposure Prophylaxis: Oseltamivir 75 mg once daily for 10 days is recommended for close contacts of confirmed influenza cases in specific high-risk settings: nursing home or long-term care facility outbreaks, household contacts of confirmed influenza who are at high risk for complications, and severely immunocompromised individuals for whom vaccination is inadequate. Pre-exposure antiviral prophylaxis (oseltamivir 75 mg daily throughout the influenza season) may be considered for severely immunocompromised patients who cannot be vaccinated effectively and are at very high risk of fatal influenza.

Treatment Priority — Who Should Receive Antivirals: All hospitalized patients with confirmed or suspected influenza, all patients with severe or progressive illness, and all high-risk outpatients (age ≥65, pregnancy, extreme obesity BMI ≥40, chronic medical conditions, immunocompromised) should receive antivirals promptly — without waiting for confirmatory test results if clinical suspicion is high. Healthy, non-high-risk outpatients with mild-to-moderate uncomplicated influenza may be treated or observed based on symptom severity and timing, in shared decision-making with the patient.

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Home & Supportive Care

The foundation of influenza management — even when antiviral therapy is prescribed — is supportive care. For the vast majority of otherwise healthy individuals, influenza is a self-limited illness that resolves within 7–10 days with proper supportive measures. These measures reduce symptom severity, prevent complications, and speed functional recovery.

Rest: Perhaps the single most important intervention. Physical rest reduces the metabolic and cardiorespiratory demands placed on a body already taxed by fever and viral-mediated inflammation. Patients who attempt to "push through" influenza and maintain normal activity often experience prolonged illness and higher complication rates. The profound fatigue influenza produces is both a symptom and a biological signal — the body's mechanism for enforcing rest during active viral replication. Patients should plan on 5–7 days of significantly reduced activity.

Hydration: Fever (insensible losses), sweating, reduced oral intake, and respiratory losses all increase fluid requirements during influenza. Adults should aim for 8–10 glasses (2–2.5 liters) of fluid daily — water, clear broths, electrolyte solutions, diluted juices. Oral rehydration solutions (ORS) are preferred when vomiting or significant sweating has caused electrolyte depletion. Patients should monitor urine output and color as indicators of hydration status. Dehydration worsens fatigue, headache, and nausea and increases complication risk, particularly renal and cardiovascular.

Fever and Pain Management: Acetaminophen (Tylenol) and ibuprofen are both effective for fever reduction and myalgia relief. Ibuprofen should be used cautiously in dehydrated patients due to the risk of acute kidney injury. Aspirin and aspirin-containing products (e.g., Pepto-Bismol, Alka-Seltzer) are absolutely contraindicated in children and adolescents under age 18 with any viral illness — including influenza — due to the risk of Reye syndrome, a rare but potentially fatal hepatic encephalopathy. Adults without aspirin contraindications may take aspirin, but acetaminophen or ibuprofen are generally preferred. Alternating acetaminophen and ibuprofen can provide more consistent fever and pain control than either agent alone.

Cough Management: Honey (1–2 teaspoons in warm water or tea) has been shown in randomized trials to modestly reduce cough frequency and severity; it is safe and well-tolerated in adults and children over 1 year of age. Honey must never be given to infants under 12 months due to the risk of infant botulism. Over-the-counter cough suppressants containing dextromethorphan have modest evidence for symptom relief in adults but should be used cautiously in children (dosing errors, limited evidence). Cough from post-influenza airway inflammation may persist 2–3 weeks and is not a sign of treatment failure or worsening.

Nasal Symptoms: Saline nasal irrigation (using a neti pot or nasal saline spray) reduces mucosal edema, clears debris and viral particles, and may reduce symptom duration. It is safe and well tolerated. Decongestants (pseudoephedrine, oxymetazoline nasal spray) can reduce nasal congestion but should be used with caution in patients with hypertension or cardiovascular disease. Oxymetazoline nasal spray should not be used for more than 3 consecutive days to avoid rebound congestion.

Isolation and Return to Activities: Infected individuals should remain at home and avoid contact with others — particularly elderly relatives, young children, and immunocompromised individuals — until they have been fever-free for at least 24 hours without the use of fever-reducing medications. This is the standard CDC guidance for return to work, school, and public activities. Wearing a surgical mask when contact with vulnerable individuals cannot be avoided may reduce transmission risk even after the fever-free period.

Emergency Warning Signs Requiring Immediate Medical Attention: Parents and patients should seek emergency care for: difficulty breathing or shortness of breath at rest; persistent chest pain or pressure; new confusion or altered consciousness; severe or persistent vomiting preventing fluid intake; signs of dehydration (no urination for 8 hours, dry mouth, dizziness on standing); bluish discoloration of lips or fingernails; symptoms that appeared to improve but then return with worsening fever or respiratory distress (suggests secondary bacterial pneumonia superimposed on resolving influenza).

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Complications & High-Risk Groups

While most cases of influenza resolve without serious sequelae, complications can be severe and life-threatening, particularly in defined high-risk populations. Understanding the spectrum of influenza complications guides clinical triage and preventive strategies.

Pulmonary Complications:

Cardiovascular Complications: Influenza increases the risk of acute myocardial infarction — a population-based study found a 6-fold higher rate of MI in the week following influenza diagnosis compared with control periods. Mechanisms include pro-inflammatory cytokine surge destabilizing coronary plaques, increased cardiac oxygen demand from fever and tachycardia, and direct viral myocardial injury. Myocarditis and pericarditis occur in a small proportion of cases (estimated 1 per 100,000) and likely contribute to some sudden cardiac deaths associated with influenza. Annual influenza vaccination is associated with reduced cardiovascular events in high-risk cardiac patients.

Neurological Complications: Influenza-associated encephalitis/encephalopathy is a rare but severe complication, occurring predominantly in children. It presents as altered consciousness, seizures, and focal neurological deficits, and carries significant mortality and long-term neurological morbidity. Reye syndrome — hepatic encephalopathy with mitochondrial dysfunction — was historically associated with aspirin use during influenza in children and is now rare since this association became widely recognized and aspirin was removed from pediatric viral illness management. Febrile seizures, while frightening, are generally benign and more common in young children with influenza due to the high fevers produced. Guillain-Barré syndrome has been epidemiologically associated with influenza infection (and very rarely with influenza vaccination, particularly the 1976 swine flu vaccine).

Musculoskeletal Complications: Influenza B (less commonly A) can cause acute myositis, presenting with severe bilateral calf pain, weakness, and markedly elevated serum creatine kinase. Myoglobinuria from severe rhabdomyolysis can lead to acute kidney injury. Aggressive hydration is the mainstay of treatment.

High-Risk Groups for Severe Disease and Death:

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Prevention & Vaccination

Annual influenza vaccination is the cornerstone of influenza prevention and the single most effective public health intervention for reducing influenza morbidity and mortality at both individual and population levels. The US Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for everyone aged 6 months and older, with rare exceptions.

Mechanisms of Vaccine-Induced Protection: Influenza vaccines elicit antibodies primarily against the hemagglutinin surface protein. Anti-HA antibodies at sufficient titers block viral attachment to sialic acid receptors on respiratory epithelial cells, preventing infection. Anti-NA antibodies limit viral replication and shedding. Vaccines also prime T-cell responses (CD4+ and CD8+), which contribute to clearance of infected cells and provide cross-reactive protection against antigenically drifted strains — a component of immunity that serum antibody titers alone do not fully capture. Cell-mediated immunity is particularly important in older adults, who generate lower antibody titers from vaccination.

Vaccine Types Currently Available in the US:

Vaccine Timing and Delivery: The optimal timing for annual influenza vaccination is before the end of October in the northern hemisphere, allowing time for the immune response to develop before peak influenza activity. Vaccination after October still provides meaningful protection and should not be withheld for late presenters — influenza activity often continues through March. Immunity develops within approximately 2 weeks of vaccination. Annual re-vaccination is required because of antigenic drift, the short duration of vaccine-induced immunity, and the need to update vaccine strains annually.

Vaccine Effectiveness Challenges: Several factors reduce real-world vaccine effectiveness compared with idealized efficacy estimates. Antigenic mismatch between vaccine strains (selected in February for the following season) and the strains that ultimately circulate is the most important factor. Egg-adaptation mutations — particularly in H3N2 HA — arise during the egg-based manufacturing process and can reduce the immunological match to wild-type circulating strains. Original antigenic sin (immune imprinting) — the tendency of the immune system to respond preferentially to antigens resembling those encountered early in life — may blunt responses to novel strains in older individuals. Despite these limitations, even partially effective vaccination reduces influenza complications, hospitalizations, and deaths at the population level.

Non-Vaccine Prevention Measures:

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Pandemic Influenza

Influenza pandemics occur when a novel influenza A subtype emerges with three concurrent characteristics: the virus is antigenically novel enough that the human population has little or no pre-existing protective immunity; the virus causes disease in humans; and the virus is capable of efficient and sustained human-to-human transmission. When all three conditions are met, the virus can spread globally before vaccine development and deployment can provide meaningful protection — as occurred in all four influenza pandemics of the 20th and 21st centuries.

Historical Pandemics:

Current Pandemic Concerns:

Global pandemic preparedness infrastructure — including WHO's Global Influenza Surveillance and Response System (GISRS), national strategic stockpiles of antivirals, pre-pandemic vaccine candidates against H5 and H7 subtypes, and international rapid-response frameworks developed after 2009 — aims to reduce the time from pandemic emergence to vaccine deployment and mitigate impact. The 2009 pandemic demonstrated that modern science can develop a matched vaccine within 6 months, though distribution and uptake remain logistical challenges.

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Key Research Papers

Foundational & Epidemiology

  1. Iuliano AD, Roguski KM, Chang HH, et al. Estimates of global seasonal influenza-associated respiratory mortality: a modelling study. Lancet. 2018;391(10127):1285-1300. PMID 29248255. DOI: 10.1016/S0140-6736(17)33293-2
  2. Thompson WW, Shay DK, Weintraub E, et al. Mortality associated with influenza and respiratory syncytial virus in the United States. JAMA. 2003;289(2):179-186. PMID 12517228. DOI: 10.1001/jama.289.2.179
  3. Johnson NP, Mueller J. Updating the accounts: global mortality of the 1918-1920 "Spanish" influenza pandemic. Bull Hist Med. 2002;76(1):105-115. PMID 11875246. DOI: 10.1353/bhm.2002.0022

Clinical Diagnosis & Presentation

  1. Monto AS, Gravenstein S, Elliott M, et al. Clinical signs and symptoms predicting influenza infection. Arch Intern Med. 2000;160(21):3243-3247. PMID 11088084. DOI: 10.1001/archinte.160.21.3243
  2. Carrat F, Vergu E, Ferguson NM, et al. Time lines of infection and disease in human influenza: a review of volunteer challenge studies. Am J Epidemiol. 2008;167(7):775-785. PMID 18230677. DOI: 10.1093/aje/kwm375

Antiviral Treatment

  1. Jefferson T, Jones MA, Doshi P, et al. Oseltamivir for influenza in adults and children: systematic review of clinical study reports and summary of regulatory comments. Cochrane Database Syst Rev. 2014;(4):CD001137. PMID 24718923. DOI: 10.1002/14651858.CD001137.pub4
  2. Hayden FG, Sugaya N, Hirotsu N, et al. Baloxavir Marboxil for Uncomplicated Influenza in Adults and Adolescents. N Engl J Med. 2018;379(10):913-923. PMID 30184455. DOI: 10.1056/NEJMoa1716197

Vaccination

  1. DiazGranados CA, Dunning AJ, Kimmel M, et al. Efficacy of High-Dose versus Standard-Dose Influenza Vaccine in Older Adults. N Engl J Med. 2014;371(7):635-645. PMID 25119609. DOI: 10.1056/NEJMoa1315727
  2. Grohskopf LA, Alyanak E, Ferdinands JM, et al. Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2021-22 Influenza Season. MMWR Recomm Rep. 2021;70(5):1-28. PMID 34448800. DOI: 10.15585/mmwr.rr7005a1
  3. Skowronski DM, De Serres G. Is routine influenza immunization warranted in early pregnancy? Vaccine. 2009;27(35):4754-4770. PMID 19576955. DOI: 10.1016/j.vaccine.2009.03.079
  4. Klein SL, Jedlicka A, Pekosz A. The Xs and Y of immune responses to viral vaccines. Lancet Infect Dis. 2010;10(5):338-349. PMID 20417129. DOI: 10.1016/S1473-3099(10)70049-9

Pandemic & Severe Disease

  1. Domínguez-Cherit G, Lapinsky SE, Macias AE, et al. Critically Ill Patients With 2009 Influenza A(H1N1) in Mexico. JAMA. 2009;302(17):1880-1887. PMID 19822628. DOI: 10.1001/jama.2009.1536

PubMed Live Searches

  1. Influenza antiviral treatment oseltamivir
  2. Influenza vaccine effectiveness
  3. Influenza complications pneumonia
  4. Influenza pregnancy outcomes
  5. Pandemic influenza H5N1 H1N1
  6. Influenza elderly high-dose vaccine
  7. Influenza myocardial infarction cardiovascular risk
  8. Influenza rapid diagnostic test sensitivity

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Connections

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