An influenza pandemic, or world-wide outbreak, advances through 3 periods—interpandemic, pandemic alert, and pandemic—and their respective phases defined by the World Health Organization (TABLE 1). Your responsibilities would be different in each of these periods (TABLE 2), requiring you to stay current on the progression of the disease and changing recommendations coming from the Centers for Disease Control and Prevention (CDC) and state and local public health departments.
A pandemic would be caused by the emergence of a new strain of influenza A. This strain could be the avian strain described in the May 2005 Practice Alert,1 “The growing threat of avian influenza,”or another novel strain.
This column describes the family physician’s role in a pandemic and includes advice on diagnosis, treatment, and prevention of disease transmission. It is based on recent recommendations from the CDC.2
Major differences between pandemic flu and a regular flu season
Vaccine shortage. Unless faster vaccine production methods are developed, there will probably be little to no vaccine initially, and once vaccine production commences the amount produced will not keep up with the need. This will necessitate prioritizing vaccine administration, forcing us to weigh societal infrastructure needs (fire-fighters, health care workers, police, etc) against those of individuals at high risk of complications.
In addition, 2 doses of vaccine 1 month apart will be needed for full protection. (Note: There is an approved provisional plan through the Advisory Committee on Immunization Practices [ACIP] and the National Vaccine Advisory Committee [NVAC] for vaccine prioritization.)
Antiviral shortage. There will also likely be a shortage of antiviral medication. Amantadine (Symmetrel) and rimantadine (Flumadine)—antivirals recommended for use against influenza A—have reduced efficacy against avian influenza, and the same may be true with any other novel strain.
Other antivirals if they are effective and available, will be used to treat acute infections and to prevent infection in those exposed and/or at high risk of complications and will be administered according to a prioritization schedule. Recommendations for prioritization of both vaccine and antivirals will come from ACIP/NVAC and the Secretary of the Department of Health and Human Services. The recommendations will be implemented by the CDC and state and local health departments, but may change as the pandemic evolves, depending on the number of people and age groups infected and the rates of morbidity and mortality.
Complicating factors. A common influenza strain could circulate at the same time as a pandemic strain, complicating the diagnostic and epidemiological picture. Office-based, rapid diagnostic tests cannot distinguish between influenza A strains. Finally, if pandemic flu exhibits the expected high rates of proliferation and mortality seen in past pandemics, our current hospital capacity will be strained and likely exceeded.
TABLE 1
WHO global pandemic phases
| INTERPANDEMIC PERIOD |
| Phase 1 No new influenza virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may exist in animals but the risk of human infection or disease is considered low. |
| Phase 2 No new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease. |
| PANDEMIC ALERT PERIOD |
| Phase 3 Human infection with a new sub-type has occurred but no human-to-human spread has occurred, or at most there have been rare instances of spread to a close contact. |
| Phase 4 Small clusters with limited human-to-human transmission are detected, but spread is highly localized, suggesting that the virus is not well adapted to humans. |
| Phase 5 Larger clusters but human-to-human spread is still localized, suggesting the virus is becoming increasingly better adapted to humans but may not yet be fully transmissible. |
| PANDEMIC PERIOD |
| Phase 6 Transmission increases and is sustained in the general population. |
| POSTPANDEMIC PERIOD |
| Return to Phase 1 |
TABLE 2
Family physician responsibilities
| INTERPANDEMIC AND PANDEMIC ALERT PERIODS |
| Become familiar with case definitions |
| Know procedures for screening, infection control, and laboratory testing |
| Know antiviral regimens for Avian and other novel influenza viruses |
| Notify local public health authorities about suspected and confirmed novel influenza cases |
| Collect recommended specimens for diagnosis of novel influenza strains and have them forwarded to designated public health laboratories |
| PANDEMIC PERIOD |
| Regularly review updates on case definitions and recommendations for screening, laboratory testing and treatment |
| Report pandemic influenza cases as requested by the public health department |
| Collect specimens as requested by the public health department for ongoing surveillance and have them forwarded to designated public health laboratories |
| Report atypical cases, prophylaxis failures, and other abnormal cases to the public health department |
Back to basics
Even with a limited supply of vaccine and antiviral medication, useful advice can still be given to individuals and the public to help them protect them and others from infection should a pandemic occur. People should be advised to: