A pandemic can start when three conditions have been met– (1) a new influenza virus subtype emerges, (2) it infects humans, causing serious illness, and (3) it spreads easily and sustainably among humans. For example, the H5N1 avian flu virus meets the first two conditions: it is a new virus for humans, and it has infected more than 100 humans, killing over half of them. No one will have immunity if and when an H5N1-like virus emerges.
The risk that the H5N1 virus will acquire the ability for efficient and sustained human-to-human transmission (i.e., the final condition for a pandemic) will continue as long as opportunities for human infection occur (this could be years). If this final condition occurs, an H5N1 avian flu pandemic (world-wide epidemic) will be the most devastating natural disaster of our lifetimes. [ How bad might this be? Assume 20% of the population gets the flu. Further assume that the fatality rate ranges from 2.5% to 20%. Then, world fatalities would range from 30 million to 240 million (normally, an estimated 250,000 to 500,000 annual deaths from flu occur worldwide); U.S. fatalities, 1.5 million to 12 million (usually, 36,000 per year die of flu in the U.S.). Research has shown that the Spanish flu virus that killed 50 million people in 1918-19 was probably a strain that originated in birds. Scientists have found that the 1918 virus shares genetic mutations with H5N1. See http://www.nature.com/news/2005/051003/full/437794a.html.]

What can be done by local public entities?

Report Communicable Diseases
Practice Basic Infection Control
Use Personal Protective Equipment
Ensure Vaccination with Seasonal Flu Vaccine
If Needed, Ensure Administration of Antiviral Drugs for Prophylaxis
Engage in Surveillance and Monitoring of Workers
Ensure Evaluation of Ill Workers
Reporting of Communicable Diseases

For example, the California Code of Regulations, Title 17, Section 2500, requires the report of communicable diseases and conditions to the local health department. http://www.longbeach.gov/civica/filebank/blobdload.asp?BlobID=9178

On a national scope, the CDC summarizes it recommendations with respect to H5N1 at http://www.cdc.gov/flu/avian/ . Briefly, the CDC interim recommendations are based on optimal precautions for protecting individuals involved in the response to an outbreak of avian influenza. It is considered prudent to take precautions to the extent feasible when individuals have contact with avian influenza virus as part of control and eradication activities (the following recommendations are copied from http://www.cdc.gov/flu/avian/professional/protect-guid.htm . Although these recommendations are tailored to poultry handlers dealing with infected birds, in the event the disease mutates to human-to-human transmission, analogous recommendations would be prudent.).

Basic Infection Control

Educate workers about the importance of strict adherence to and proper use of hand hygiene after contact with infected or exposed [people or] poultry, contact with contaminated surfaces, or after removing gloves. Hand hygiene should consist of washing with soap and water for 15-20 seconds or the use of other standard hand-disinfection procedures as specified by state government, industry, or USDA outbreak-response guidelines.
Ensure that personnel have access to appropriate personal protective equipment (PPE), instructions and training in PPE use, and respirator fit-testing.

Personal Protective Equipment

Disposable gloves made of lightweight nitrile or vinyl or heavy duty rubber work gloves that can be disinfected should be worn. To protect against dermatitis, which can occur from prolonged exposure of the skin to moisture in gloves caused by perspiration, a thin cotton glove can be worn inside the external glove. Gloves should be changed if torn or otherwise damaged. Remove gloves promptly after use, before touching non-contaminated items and environmental surfaces.
Protective clothing, preferably disposable outer garments or coveralls, an impermeable apron or surgical gowns with long cuffed sleeves, plus an impermeable apron should be worn.
Disposable protective shoe covers or rubber or polyurethane boots that can be cleaned and disinfected should be worn.
Safety goggles should be worn to protect the mucous membranes of eyes.
Disposable particulate respirators (e.g., N-95, N-99, or N-100) are the minimum level of respiratory protection that should be worn. This level or higher respiratory protection may already be in use in poultry operations due to other hazards that exist in the environment (e.g., other vapors and dusts). Workers must be fit-tested to the respirator model that they will wear and also know how to check the face-piece to face seal. Workers who cannot wear a disposable particulate respirator because of facial hair or other fit limitations should wear a loose-fitting (i.e., helmeted or hooded) powered air purifying respirator equipped with high-efficiency filters.
Disposable PPE should be properly discarded, and non-disposable PPE should be cleaned and disinfected as specified in state government, industry, or USDA outbreak-response guidelines. Hand hygiene measures should be performed after removal of PPE.

Vaccination with Seasonal Influenza Vaccine

Unvaccinated workers should receive the current season’s influenza vaccine to reduce the possibility of dual infection with avian and human influenza viruses. There is a small possibility that dual infection could occur and result in reassortment. The resultant hybrid virus could be highly transmissible among people and lead to widespread infections. Vaccination of all residents of affected areas is not supported by current epidemiologic data.

Administration of Antiviral Drugs for Prophylaxis

Workers should receive an influenza antiviral drug daily for the duration of time during which direct contact with infected [people or] poultry or contaminated surfaces occurs. The choice of antiviral drug should be based on sensitivity testing when possible. In the absence of sensitivity testing, a neuraminidase inhibitor (oseltamavir) is the first choice since the likelihood is smaller that the virus will be resistant to this class of antiviral drugs than to amantadine or rimantadine. For further information about the use of antiviral drugs for influenza, see “Prevention and Control of Influenza”. Recommendations of the Advisory Committee on Immunization Practices (ACIP).” MMWR 2003; 52(RR08): 1-36. Available at www.cdc.gov/mmwr/preview/mmwrhtml/rr5208a1.htm.
[Two drugs (in the neuraminidase inhibitors class), oseltamivir (commercially known as Tamiflu) and zanamivir (commercially known as Relenza) can reduce the severity and duration of illness caused by seasonal influenza. The efficacy of the neuraminidase inhibitors depends on their administration within 48 hours after symptom onset. For cases of human infection with H5N1, the drugs may improve prospects of survival, if administered early, but clinical data are limited. The H5N1 virus is expected to be susceptible to the neuraminidase inhibitors.]

Surveillance and Monitoring of Workers

Instruct workers to be vigilant for the development of fever, respiratory symptoms, and/or conjunctivitis (i.e., eye infections) for 1 week after last exposure to avian influenza-infected or exposed birds or to potentially avian influenza-contaminated environmental surfaces.
Individuals who become ill should seek medical care and, prior to arrival, notify their health care provider that they may have been exposed to avian influenza. In addition, employees should notify their health and safety representative.
With the exception of visiting a health care provider, individuals who become ill should be advised to stay home until 24 hours after resolution of fever, unless an alternative diagnosis is established or diagnostic test results indicate the patient is not infected with influenza A virus.
While at home, ill persons should practice good respiratory and hand hygiene to lower the risk of transmission of virus to others. For more information, visit CDC’s “Cover Your Cough” website.

Ensure Evaluation of Ill Workers

Workers who develop a febrile respiratory illness should have a respiratory sample (e.g., nasopharyngeal swab or aspirate) collected.
The respiratory sample should be tested by RT-PCR for influenza A, and if possible for H1 and H3. If such capacity is not available in the state, or if the result of local testing is positive, then CDC should be contacted and the specimen should be sent to CDC for testing.
Virus isolation should not be attempted unless a biosafety level 3+ facility is available to receive and culture specimens.
Optimally, an acute- (within 1 week of illness onset) and convalescent-phase (after 3 weeks of illness onset) serum sample should be collected and stored locally in case testing for antibody to the avian influenza virus should be needed.
In addition, the USDA summarizes it recommendations at http://www.aphis.usda.gov/lpa/pubs/fsheet_faq_notice/fs_ahhpaiplan.html , and a summarization of the World Health Organization’s (WHO’s) views can be read at http://www.who.int/csr/resources/publications/influenza/WHO_CDS_CSR_GIP_05_8-EN.pdf .