In the United States, the likelihood of substantial disparities in access to timely and appropriate care under infl uenza pandemic conditions is high, given long-standing and persistent disparities in access to medical care. For example, persons with low income are ≈2× as likely as those with higher incomes to lack a usual source of healthcare (24) . Similarly, non-Hispanic black and Hispanic persons are signifi cantly less likely than non-Hispanic white persons to report having a usual primary care provider (10). Among persons who do report having a usual source of care, those who are poor or near poor and those who are non-Hispanic black or Hispanic are 2.5-4× as likely as their relatively higher income and white counterparts to rely on a hospitalbased source of primary care (24) . These same groups are also more likely to report having diffi culty obtaining timely appointments for illness or injury, which suggests problems with access to care even among those with a usual source of healthcare (10) . Language and cultural barriers to seeking and receiving medical care also may contribute to disparities. In emergency departments, for example, interpreters are frequently unavailable or underused, which has potentially adverse implications for patients' understanding of their disease or treatment and for clinical decision making Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 14, No. 5, May 2008 711 Table. Factors that could contribute to health disparities among socioeconomic and racial/ethnic groups during an influenza pandemic Differences in exposure to influenza virus Crowding in households, medical facilities, public transportation Occupational factors such as inability to work from home, dependence on childcare outside of the home Differences in susceptibility to influenza disease, once exposed to the virus Host factors, including preexisting immunity, age, other underlying diseases or conditions, smoking, nutritional status, stress Vaccination status, reflecting differences in vaccine seeking and acceptance and in vaccine availability Differences in timely effective treatment, once influenza disease has developed Access to outpatient and inpatient medical care Care-seeking attitudes and behavior Financial obstacles, including lack of adequate insurance coverage Logistic obstacles, including transportation, language Quality of care Availability of antiviral treatments Appropriate inpatient treatment and quality of care (25) . In addition, the large numbers of persons who lack health insurance, as well as those who lack documentation of US citizenship, often delay seeking care because they are concerned about paying for the care or encountering legal diffi culties. Evidence from previous outbreaks suggests that antiviral drugs may be effective for treatment (26) and prevention (27) of pandemic infl uenza, and current antiviral drugs seem to be biologically effective against 1918 and 1918like viruses (28) . Because vaccine may not be available when a pandemic begins, experts have suggested that the antiviral drug oseltamivir should be stockpiled for use during a pandemic infl uenza outbreak. Recent models suggest that early use of oseltamivir may contain outbreaks if certain criteria regarding transmissibility and compliance are met (29) . However, experience with nonpandemic infl uenza indicates that oseltamivir must be given early during symptom development for it to have any substantial biological effect (30) ; modest delays may vitiate the treatment effectiveness (31) . Although plans for release and distribution of antiviral drugs are still being fi nalized, overcoming long-standing disparities in access to timely treatment by socioeconomic status, race/ethnicity, ability to speak English, and legal status will present numerous challenges to ensuring equal access to such drugs during a pandemic.