INFLUENZA
Identification:
Acute viral disease of respiratory tract characterized by fever, headache, chills, myalgia (muscular pain), exhaustion, coryza (nasal discharge), sore throat, and cough. Cough is often severe and protracted but other symptoms are usually self-limited with recovery in two to seven days. Gastro-intestinal tract manifestations may occur, particularly in children. Epidemics may develop rapidly. Serious complications, especially in the elderly and immunocompromised include viral and bacterial pneumonia. People with chronic cardiac, pulmonary, renal, or metabolic disease are also at risk.
Every year: 5 million Canadians will be infected
(one in six)
50,000 will be hospitalized
(1/100>65 yrs)
4500 will die
7% of 2- 6 yr olds will have acute
otitis media
See “Let’s Beat the Flu” Ministry of Health Fact Sheet!
(being faxed separately)
Infectious Agent:
Three types of influenza virus - A, B, C
Reservoir:
Man.
Geographical Distribution:
In the tropics influenza can occur throughout the year. In temperate regions of the Southern Hemisphere (Parts of Australia and S America) most activity occurs from April through September. In countries in the Northern Hemisphere such as Canada and the States influenza activity occurs from November through April. Note that CDC investigations have concluded that outbreaks can occur throughout the year in tourists travelling in large groups regardless of season.
Mode of Transmission:
Airborne spread among crowded populations in enclosed spaces. Also occurs by direct contact through droplet spread. Can survive on objects such as phones and cutlery for up to two days and on tissue and clothing for 8 to 10 hours.
Incubation Period:
One to five days.
Period of Communicability:
Probably three to five days from clinical onset in adults. Up to seven days in young children. There is no carrier state.
Susceptibility:
When new subtypes appear - all are susceptible.
Prevention:
Refer to the annual CCDR statement for recommendations regarding recipients- recommendations for usage may change as new research becomes available. At this time influenza vaccine may be administered to any healthy child (over 6 months of age- less immunogenic in those under 6 months), adolescent or adult for whom contraindications are not present. In efforts to reduce the morbidity and mortality associated with this disease and the impact of illness in our communities, immunization programs have focused on those at high risk of complications, those capable of transmitting to individuals at high risk of complications and those who provide essential services. However, due to the morbidity and costs associated with seasonal interpandemic influenza illness healthy adults and children are encouraged to receive the vaccine.
Vaccination is considered safe for pregnant women at all stages of pregnancy and for breastfeeding mothers. It is recommended for those who are characterized by any of the conditions listed under recommended recipients. NACI concludes that “there is insufficient evidence at this time to recommend the routine immunization of otherwise healthy Canadian women who are pregnant during influenza season”
For travel, immunization with the most current available vaccine should be considered for all individuals who wish to avoid influenza while traveling to areas where influenza is likely to be circulating. Health Canada concludes “there is insufficient evidence at this time to advise in favour or against the routine re- immunization of travelers who were immunized in the fall and who are subsequently traveling to regions where influenza may be circulating in the late spring and summer months.
Preparations:
See Product Information insert.
(being faxed separately)
The vaccine should be refrigerated at a temperature between 2 and 8 degrees Celsius. The product should not be frozen.
The vaccine may be given at the same time as other vaccines provided different sites and administration sets are used.
For specific questions and concerns re adverse reactions refer to product monograph. The vaccine cannot cause influenza because it is does not contain live virus. Soreness at the injection site lasting up to 2 days is common and rarely interferes with normal activity. Fever, malaise and myalgia may occur within 6 to 12 hours after vaccination and last 1 to 2 days especially in young adults receiving the whole virus vaccine and those receiving vaccine for the first time. Allergic responses are rare and are most likely a result of hypersensitivity to a component of the vaccine most likely residual egg protein. Immunization is contraindicated in those people who have had an anaphylactic reaction to a previous dose or who have a known anaphylactic hypersensitivity to eggs. Those with acute febrile illness should not be immunized until their symptoms have abated.
Reporting Case Definition:
Clinically compatible signs and symptoms with:
a) laboratory confirmation by detection or isolation of influenza virus in pharyngeal or nasal secretions- virus can be isolated from throat and nasopharyngeal swabs obtained within 3 days of onset of illness- a minimum of 48 hours is required to demonstrate virus and another 1 to 2 days for type- this is most helpful in defining the etiology of local epidemics; or
b) demonstration of a four-fold or greater increase in hemagglutination antibody titres to influenza between acute and convalescent titres- acute specimen taken less than 5 days from onset and convalescent 10 to 21 days following onset (21 preferred)- diagnosis requires at least a 4-fold rise in antibody titre; or
c) an epidemiologic link to at least one laboratory confirmed case.
Note - rapid diagnostic testing is now available for Influenza A- done by most hospitals – NP swab done and results possible in an hour depending on individual labs- good sensitivity and specificity to Inf A and RSV- always send on for culture to Public Health Lab- can take up to 7 days to type – a negative screen may culture if there is a scanty amount of virus present.
REFERENCES
WHO – 2002
Control of Communicable Disease Manual – James Chin – 17th edition -2000
Canadian Immunization Guide Health Canada-Sixth edition-2002
Red Book 2000 – AAP – 25th edition
Epidemiology and Preventing of Vaccine – Preventable Diseases – 6th edition -Jan 2000 - CDC
CCDR- March 1, 1998 – “Measles Surveillance”
May 15, 2002 – “Global Measles Mortality Reduction”
Health Canada – Travel Medicine Program – PPHB-2002/07/02
“Influenza in Hospitals” – Dr. Allison McGeer -3/02/12- Power Point Presentation
Statement on Influenza Vaccination for the 2002-2003 season – CCDR
CDC – “Traveller’s Health” – Feb. 1999