China. Initial case definition anddiagnosis required a combination of symptoms (fever, dry cough and pneumonia) and positive chest CT (computerized tomography) results. The pneumonia associated with this disease resulted in what are described as "ground glass opacities" in chest CT scans. The disease, later named CoVid-19, by the WHO was determined to be viral in origin and likely infectious by person to person contact.As concerns increased about the disease spreading screening programs at airports looked for increased temperatures and coughing in travelers. It was thought at the time only symptomatic cases were contagious.

Once the causative virus (SARS CoV-2) was identified and genotyped ,positive results on a RT-PCR test detecting viral RNA was added to case definition - although in some places (such as China) cases were only counted as "confirmed" if also symptomatic (generally cough, fever, shortness of breath). The PCR tests amplifies any of the virus's RNA, so even if there is a small amount present or even if it is fragmented it can still, in theory, be detected. In practice the test required some skill to collect the sample and generally would not be positive until at least 4-5 days after exposure. In addition, the test us very uncomfortable(although very low risk) procedure as a swab must be inserted deep into the nasopharyngeal cavity.

Once available in the US, the RT-PCR test was used as the gold standard for diagnosis as opposed to chest CTs. In order to "qualify" for testing patients had to be symptomatic and have epidemiologic evidence of contact with someone known to have been in Wuhan.Tests were only performed by the CDC and every sample was tested twice. The test was considered to be both highly sensitive and highly specific. Initially, using these criteria the testing only identified as positive about 5% of those tested Nevertheless, by February the first case was identified in a person who had no contact with anyone from Wuhan and as testing was broadened to by based only on symptoms it was clear that community spread had been taking place for some time in the US. It also became apparent that some cases had developed with no known symptomatic contacts. Some studies suggested suggestions that chest CT scans were more sensitive, and they could detect CoVid 19 earlier than the RT-PCR. The argument against using CT scans was that results were very dependent on the training of the readers; the ground glass opacities were not completely specific to CoVid-19 and using them exposed the patients to radiation and the healthcare providers with more patient contact. Where and when RT-PCR tests were widely available they could be used for screening. South Korea screened several 100,000 people following an initial outbreak there and the age distribution of the infection were described. In NYC, at the height on the pandemic there in April 2020 all pregnant women were tested before being admitted for delivery. Almost 15%of these women at 2 major NYC hospitals were positive.

1.Referring to the principles given in the Appendix 1 below discuss whether or not The US should have instituted a mass screening program using the RT-PCR tests as soon as there was evidence of community spread in Washington state. (4pts)

Appendix 1

The following 10 principles of successful mass screening programs were proposed by Wilson and Jungner of the World Health Organization in 1968:

1.The condition being sought is an important health problem for the individual and the community.

2.There is an acceptable form of treatment for patients with recognizable disease.

3.The natural history of the condition, including its development from latent to declared disease, is adequately understood;

4.There is a recognizable latent or early symptomatic stage.

5.There is a suitable screening test or examination for detecting the disease at the latent or early symptomatic stage, and this test is acceptable to the population.

6.The facilities required for diagnosis and treatment of patients revealed by the screening program are available.

7.There is an agreed policy on whom to treat as patients.

8.Treatment at the pre-symptomatic, borderline stage of a disease favorably influences its course and prognosis.

9.The cost of the screening program (which would include the cost of diagnosis and treatment) is economically balanced in relation to possible expenditure on medical care as a whole.

10.Case-finding is a continuing process, not a "once and for all" project.

1b.Does this mean that only 15% of pregnancies were potentially impacted by CoVid infections? (assume the testing was accurate at this point) (2pts)