COVID-19 What the Government Knew Post #10

Planning Assumptions*

Given the difficulty associated with estimating timing or impact, pandemic planning is based on the following assumptions about viral epidemiology and human susceptibility:

 

• Delays in availability of vaccines and shortages of antiviral drugs are likely, particularly early in the pandemic.

 

• The seasonality of a pandemic cannot be predicted with certainty. With seasonal influenza, peak disease usually occurs during December through March in the United States. During the 2009 A(H1N1) pandemic, the first cases were identified in April, and widespread US community outbreaks first began in August, with illness peaking in October 2009, months earlier than is routinely seen with seasonal influenza.

 

• The novel virus will have the ability to spread rapidly worldwide.

 

• If the pandemic is characterized by severe disease, it will have the potential to disrupt national and community infrastructures (including healthcare, transportation, commerce,utilities, and public safety) due to widespread illness, absenteeism, and death among workers and their families, as well as concern about ongoing exposure to the virus.

 

• Not all jurisdictions will experience clusters of disease simultaneously; however, near-simultaneous clusters likely will occur in many communities across the United States, thereby limiting the ability of any jurisdiction to support and assist other jurisdictions.

 

• During a pandemic, infection in a localized area can last about six to eight weeks. At least two pandemic disease waves will occur. Following the pandemic, the newly circulating virus is likely to become a regularly occurring seasonal influenza.

 

• Immunity to the novel pandemic influenza subtype will vary based on the strain of the virus, but most people will likely be susceptible, depending on whether a similar strain has circulated in previous seasons.

 

• The clinical disease attack rate could range from 20% to 30% of the overall population. Illness rates will likely vary by age group (and other epidemiologic characteristics) and could create selective pressures on segments of the community, such as nursing homes or schools.

 

• The typical incubation period (the time between acquiring the infection and becoming ill) for influenza averages two days (range is one to four days).

•Of those who become ill with influenza, up to 50% will seek outpatient medical care.

 

•The number of hospitalizations and deaths will depend on the severity of the disease and the success of steps to mitigate its transmission. Nonetheless, estimates could differ by as much as a factor of 10 between more and less severe scenarios .

 

•Risk groups for severe and fatal infections cannot be predicted with certainty. During annual fall and winter influenza seasons, infants and the elderly, people with certain chronic illnesses, people with morbid obesity, and pregnant women are usually at higher risk of complications from influenza infections than other groups. In contrast, in the 1918 pandemic, deaths were notably evident among young, previously healthy adults; in 2009, el erly people were disproportionately spared severe illness and death.

 

•People who become infected will shed the virus and transmit infection  for up to one day before the onset of illness.

 

• Viral shedding and the risk for transmission will be greatest during the first two days of illness and may persist or five to seven days.

 

• Children will shed the greatest amount of virus and, therefore, are likely to pose the greatest risk for transmission.

 

•The most severely ill people with influenza will shed the most virus for the longest period of time.

 

•One or two secondary infections will occur as a result of transmission from someone who is ill. In contrast, some estimates from past pandemics have been higher, with up to three secondary infections per primary case.

 

*From pp43-44 Pandemic Influenza Plan 2017 Update

 

 

 

circulating virus is likely to become a regularly occurri ng seasonal influenza. • Immunity to the novel pandemic influenza subtype w ill vary based on the strain of thevirus, but mos t people will likely be susceptibl e, depending on w hether a similar strain has c irculated in previous seasons.• The clini c al dis eas e attac k rate could range from 20% to 30% of the overall population. Illness r ates will likely vary by age group (and other epidemiologic characteristics) a nd could create se lective pressures on se gments of the community, such as nursing homes or schools. • The typical incubation period (the time between acquiri ng the infection and becoming ill) for influenza averages two days (range is one to f our days). •Of thos e w ho b ecome ill with influenza, up to 50% will seek outpatient medical c are. •The number o f hospitaliz ations and deaths will depend on the se verity of t he diseaseand the succe ss of steps to mitigate i ts transmission. N onetheless, es timates could differ by as much as a f actor of 10 between more and l ess severe sc enarios .•Risk gr oups for severe and fatal in f ections ca nnot be predicted with ce rtainty. Duringannual fall and winter influenza s easons, in fants and the elderly, people with certain chronic illnesses, people with morbid obesity , and pregnant women are usually at higherrisk of complications from influenza infections than other groups. In contras t, in the 1918 pandemic, deaths were notably evident among y oung, previously healthy adults; in 2009, el derly people were disproportionately spared severe illness and death. •People who become inf ected will shed v irus and transmit in f ection f or up to one day before the ons et of illness.• Viral shedding and the risk for transmission will be greatest during the first two days of illness and may persi st f or five to se ven days. • Childr en will shed the greatest amount of virus and, therefore, are likely to pos e the gr eatest risk f or transmi ssion.•The most severely ill people with influenza will shed the most virus f or the l onges t period of time. •One or two secondary inf ectio ns will occur as a r esult of transmi ssion from someone who i s ill. In c ontrast, some estimat es from past pandemi cs have been hig her, wi th up to three sec ondary inf ectio ns per p rimary c as e.Bec ause the precise impact of a future pandemi

circulating virus is likely to become a regularly occurri ng seasonal influenza. • Immunity to the novel pandemic influenza subtype w ill vary based on the strain of thevirus, but mos t people will likely be susceptibl e, depending on w hether a similar strain has c irculated in previous seasons.• The clini c al dis eas e attac k rate could range from 20% to 30% of the overall population. Illness r ates will likely vary by age group (and other epidemiologic characteristics) a nd could create se lective pressures on se gments of the community, such as nursing homes or schools. • The typical incubation period (the time between acquiri ng the infection and becoming ill) for influenza averages two days (range is one to f our days). •Of thos e w ho b ecome ill with influenza, up to 50% will seek outpatient medical c are. •The number o f hospitaliz ations and deaths will depend on the se verity of t he diseaseand the succe ss of steps to mitigate i ts transmission. N onetheless, es timates could differ by as much as a f actor of 10 between more and l ess severe sc enarios .•Risk gr oups for severe and fatal in f ections ca nnot be predicted with ce rtainty. Duringannual fall and winter influenza s easons, in fants and the elderly, people with certain chronic illnesses, people with morbid obesity , and pregnant women are usually at higherrisk of complications from influenza infections than other groups. In contras t, in the 1918 pandemic, deaths were notably evident among y oung, previously healthy adults; in 2009, el derly people were disproportionately spared severe illness and death. •People who become inf ected will shed v irus and transmit in f ection f or up to one day before the ons et of illness.• Viral shedding and the risk for transmission will be greatest during the first two days of illness and may persi st f or five to se ven days. • Childr en will shed the greatest amount of virus and, therefore, are likely to pos e the gr eatest risk f or transmi ssion.•The most severely ill people with influenza will shed the most virus f or the l onges t period of time. •One or two secondary inf ectio ns will occur as a r esult of transmi ssion from someone who i s ill. In c ontrast, some estimat es from past pandemi cs have been hig her, wi th up to three sec ondary inf ectio ns per p rimary c as e.Bec ause the precise impact of a future pandemi