Influenza A (H1N1)

Influenza is usually a respiratory infection

Transmission Regular person-to-person transmission Primarily through contact with respiratory

droplets Transmission from objects (fomites) possible

National Center for Disease Prevention and Control, DOH

Key CharacteristicsCommunicability

Viral shedding can begin 1 day before symptom onset

Peak shedding first 3 days of illness

Correlates with temperature Subsides usually by 5-7th

day in adults Infants, children and the

immuno-compromised may shed the virus longer


Incubation period Time from exposure to onset of symptoms 1 to 4 days (average = 2 days)

Seasonality In temperate zones, sharp peaks in winter months In tropical zones, circulates year-round with

seasonal increases.


Individuals at Increased Risk for Hospitalizations and Death

Elderly > 65 yearsChildren less than two yearsCertain chronic diseases

Heart or lung disease, including asthma Metabolic disease, including diabetes HIV/AIDs, other immuno-suppression Conditions that can compromise respiratory function or

the handling of respiratory secretionsPregnant women


INTENSIVE-CARE PATIENTS WITH SEVERE NOVEL INFLUENZA A (H1N1)

VIRUS INFECTION --- MICHIGAN, JUNE 2009

10 patients wiith Influenza A(H1N1) and ARDS admitted at ICU. Of the 10 patients 9 were obese (BMI>30) including 7 who are extremely obese (BMI>40). Five had pulmonary emboli; Nine had MODS. 3 patients died. Clinicians should be aware of the potential for severe complications of H1N1 virus infection in extremely obese patients.

Conclusion

Predominance of malesHigh prevalence of obesityFrequency of clinically significant pulmonary

emboli and MODS

Influenza A VirusesInfluenza A viruses categorized by subtype

• Classified according to two surface proteins

Hemagglutinin (H) – 16 known

Neuraminidase (N) – 9 known

N

H


A / Sydney / 05 / 97 (H3N2)

Nomenclature

Virus type

Strain number

Virus subtype

Place virusisolated

Year isolated


Region

Cumulative total

as of 11 October 2009

Cases* Deaths WHO Regional Office for (AFRO) 12456 70 WHO Regional Office for the (AMRO) 153697 3406 WHO Regional Office for the (EMRO) 13855 90

WHO Regional Office for (EURO) Over

61000 At least

207 WHO Regional Office for (SEARO) 39522 530 WHO Regional Office for the Western Pacific (WPRO) 118702 432

Total Over

399232 At least

4735

Influenza A (H1N1) is a novel virus

Unusual combination of genetic material from pigs, birds & humans which have re-assorted

Affects all age groupsVaccines for human seasonal flu can not

protect humans against the novel virus


Swine Influenza Viruses

RNA virusesPigs can be infected by avian influenza and

human influenza viruses as well as swine influenza viruses.

Re-assort and new viruses that are a mix of swine, human and avian influenza viruses can EMERGE


SIV

Genetic Re-assortment


Signs & Symptoms of Influenza A (H1N1)

FeverLethargyLack of appetiteCoughingRunny NoseSore throatNausea / VomitingDiarrhea


Swine H1N1 vs. Human H1N1

swine H1N1 flu virus NOT the same as human H1N1 virus

antigenically very different from human H1N1 viruses

vaccines for human seasonal flu can not protect humans from swine H1N1


Transmission: Food-Borne?

NOInfluenza A (H1N1) viruses are not

transmitted through food Safe to eat properly handled and cooked pork

and pork productsCook pork at an internal temperature of 70°C

(160°F)


Diagnosis and Laboratory Confirmation

Clinically diagnosedRespiratory Specimen

• first 4 to 5 days of illness

• can shed for 10 days or longerSpecimens sent to US CDC

• ONLY laboratory that can isolate and identify swine influenza type A virus


SpecimensUpper respiratory tract specimens as

recommended are the most appropriate. taken from the deep nostrils (nasal swab),

nasopharynx (nasopharyngeal swab), Nasopharyngeal aspirate, throat or bronchial aspirate.

Laboratory Diagnosis

Rapid Influenza Diagnostic Test

Antigen detection test that detect influenza viral nucleoprotein antigen

Can provide results within 30 minutes

Sensitivity 40-69%

CDC rRT-PCR Swine Flu Assay

Sensitivity : 99.8%Specificity: 92%

Table 1. Comparison of Available Influenza Diagnostic Tests1 Influenza Diagnostic Tests

Method Availability TypicalProcessing Time2

Sensitivity3 for 2009 H1N1 influenza

Distinguishes 2009 H1N1 influenza from other influenza A viruses?

Rapid influenza diagnostic tests (RIDT)4

Antigen detection

Wide 0.5 hour 10 – 70% No

Direct and indirect immunofluorescence assays (DFA and IFA)5

Antigen detection

Wide 2 – 4 hours 47–93% No

Viral isolation in tissue cell culture

Virus isolation

Limited 2 -10 days - Yes 6

Nucleic acid amplification tests (including rRT-PCR) 7

RNA detection

Limited8 48 – 96 hours [6-8 hours to perform test]

86 – 100% Yes

Treatment

Influenza A (H1N1) is sensitive to: Oseltamivir (tamiflu) Zanamivir

Self medication is discouraged, may induce drug resistance

Chemoprophylaxis Oseltamivir


Table 1. Antiviral medication dosing recommendations for treatment or chemoprophylaxis of novel influenza A (H1N1) infection.

(Table extracted from IDSA guidelines for seasonal influenza.)

Agent, group Treatment Chemoprophylaxis

Oseltamivir

Adults75-mg capsule twice per day

for 5 days75-mg capsule once per day

Children ≥ 12 months

15 kg or less60 mg per day divided into 2

doses30 mg once per day

16-23 kg90 mg per day divided into 2


24-40 kg120 mg per day divided into 2


>40 kg150 mg per day divided into 2


Zanamivir

AdultsTwo 5-mg inhalations (10 mg

total) twice per dayTwo 5-mg inhalations (10 mg

total) once per day

ChildrenTwo 5-mg inhalations (10 mg

total) twice per day (age, 7 years or older)

Two 5-mg inhalations (10 mg total) once per day (age, 5 years or older)

CDC Health Advisory Distributed via Health Alert Network July 09, 2009

Three Reports of Oseltamivir Resistant Novel Influenza A (H1N1) Viruses

ANTI VIRAL CHEMOPROPHYLAXIS

Post-exposure prophylaxis for health care workers, first responders and workers who did not have adequate PPE when in contact.

Anti-viral prophylaxis is not recommended to close contacts except when they belongto high risk group.

Vaccine

Process of production is underway, but may take 5 – 6 months

Seasonal influenza vaccine provides protection against the seasonal human influenza strains only


Vaccine

Supplier Vaccine Form Mercury µg/0.5 mL

Age

MedImmune(nasal spray)

Live virus 0.2 mL(nasal spray sprayer)

0 2-49 yrsb

Sanofi (IM)a Inactivated0.25 mL prefilled syringe0.5 mL prefilled syringe5 mL multidose vial

00

25

6-35 mosb > 36 mosb > 6 mosb

Novartis (IM)a 5 mL multidose vial0.5 mL prefilled syringe

25< 1.0

≥ 4 yrsb > 4 yrsb

CSL Biotherapies, Inc (IM)a

0.5 mL prefilled syringe5.0 mL multidose vial

024.5

> 18 yrs> 18 yrs

0.5 mL doses contain 15 µg hemagglutinin of the vaccine strain A/California/7/2009 (H1N1)Two doses separated by 4 weeks for children 2-9 years

(CDC. Update on influenza A (H1N1) monovalent vaccines. MMWR Morb Mortal Wkly Rep. 2009;58:1100-1101.)

INTERIM GUIDELINES NO.2: INFECTION CONTROL AND USE OF PERSONAL PROTECTIVE EQUIPMENT IN

INFLUENZA A

HEALTH CARE PERSONNEL

Standard and droplet precautions when working in direct contact

If there is risk of splashes: particulate respirator; eye protection;clean, non-sterile, long sleeved gown; sterile gloves

Frequent and proper handwashing

Isolate patient in a single room.Reinforce standard precautions with droplet

and contact precautionUse appropriate Personal Protective

Equipment for all those entering patients rooms.

Restrict number of visitors.Healthcare workers on direct contact

should monitor their own temperature 2X a day and report any febrile event.

INTERIM GUIDELINES NO.17: REVISEDCLINICAL CASE MANAGEMENT OF

INFLUENZA A(H1N1) VIRUS INFECTION

VaccinationInfluenza vaccine is the best prevention for

seasonal influenza.Inactivated viruses in the vaccine

developed from three circulating strains (generally 2 Type A and 1 Type B strain) Therefore, seasonal “flu shot” only works for 3

influenza subtypes and will not work on pandemic strains.

Live, intranasal spray vaccine for healthy non-pregnant persons 5-49 years

Inactivated, injectable vaccine for persons 6 months and olderNational Center for Disease Prevention and Control, DOH

Influenza Viruses

Classified into types A, B, and C

• Only Types A and B cause significant disease

• Types B and C limited to humans

• Type A viruses More virulent Affect many species

C Goldsmith, CDC


The FDA has approved 4 vaccine preparations. The following data highlight relevant issues:All influenza vaccine preparations in the United States for the 2009-2010 season contain residual egg protein and none contain adjuvant;Children 6 months to 9 years of age who are given influenza A (H1N1) monovalent vaccine should receive 2 doses separated by about 4 weeks; persons ≥ 10 years of age should receive 1 dose;The influenza A (H1N1) monovalent vaccines were made according to standards used for seasonal and influenza vaccines and have the same age group indications, precautions, and contraindications as vaccines that are FDA-approved for seasonal flu; preliminary data indicate that the safety and efficacy of the 2009 Influenza A (H1N1) monoclonal vaccine is the same as winter;There is minimal evidence of significant antigenic change since the first characterization of the virus in April 2009, indicating that the virus continues to be well matched with the vaccine strain; andThe vaccines of the 4 suppliers have some differences that are important to recognize:for seasonal flu vaccines;Side effects, including local pain at the injection site, were reported in 46% of recipients, and systemic reactions (headache, malaise or myalgias) were reported in 45%; the safety profile is consistent with the experience with seasonal flu vaccine;Influenza activity due to influenza A (H1N1) increased in September 2009 and is expected to continue through fall and

Children 6 months to 9 years of age should receive 2 doses separated by 3 weeks. Children 10 years and older and adults should receive 1 dose.

The following groups should receive the vaccine as soon as it becomes available:•Pregnant women;•People who live with or care for infants younger than 6 months of age;•Healthcare workers (HCWs) and emergency medical personnel;•Persons 6 months to 24 years of age;•Persons 25-64 years of age who have chronic diseases (including immunodeficiency states) that pose risk for influenza.

When more vaccine becomes available, the following persons should be vaccinated:•Healthy persons ages 25-64 years; and•Adults 65 years of age and older.

S-top spreading panic acts / thoughts.

T-amiflu panic buying (Avoid).

O-ver-reacting with vaccines.

P-rotective Equipments

S-ocial Distancing.W-ASH YOUR HANDSI-solate voluntarily.N-o Unnecessary travel. E-arly Consult.

F-lu symptom declared.L-imit Crowded areas.U-pdate yourself.

H1N1 - Dos & DON’Ts !

N. Macalintal Jr. MD, FPCP, FPCCP

Influenza A (H1N1)

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