Infectious Disease Screening

The core role of infectious disease screening is to identify the infection state before the infected person shows typical symptoms or is in the incubation period. This not only helps individuals intervene as early as possible to avoid severe illness and reduce the risk of sequelae, but also cuts off the chain of transmission at the source and avoids the outbreak of public health events.

Last year, when I was rotating in the infection department of a community health service center, I met a 62-year-old Uncle Zhang. He was found positive after adding a hepatitis C screening item to the routine physical examination at the workplace. He didn't feel any discomfort at all. After asking about the medical history, he remembered that he had a tooth extracted at a small clinic 20 years ago. It was most likely that he was infected at that time. The doctor who treated the patient said that fortunately it was discovered early. If it takes another two or three years to progress to liver cirrhosis, the difficulty and cost of treatment would be several times higher.

Nowadays, most of the infectious disease screenings that everyone is exposed to routinely include hepatitis B, hepatitis C, AIDS, and syphilis in the physical examination package. Some industries with a risk of tuberculosis exposure will also conduct tuberculin tests. Regarding the necessity of this part of screening, there have always been two voices in the industry: One group believes that there is no need for non-high-risk groups to routinely undergo this type of screening. After all, the transmission paths of most pathogens are clear. People who have no experience in blood transfusions, high-risk sexual behaviors, or unclean and invasive operations have a very low probability of infection. If it is rolled out on a large scale, it will waste already tight medical resources. ； The other school of thought is more radical and believes that the transmission paths of many infections are quite hidden. Eyebrow tattoos, ear piercings, and pedicures in informal shops may all be infected with hepatitis B and hepatitis C. Improving the coverage of routine screening can minimize the missed diagnosis rate. Nearly one-third of the people infected with hepatitis C that I have come into contact with cannot tell a clear history of high-risk exposure. From this perspective, the latter statement is not unreasonable.

If the controversy over daily screening still focuses on "whether to do it or not," the debate about screening during public health emergencies is about "how extensive it should be." During the COVID-19 epidemic in the past two years, we sometimes received notices at 2 a.m. to conduct nucleic acid tests on the entire street. We also encountered residents complaining, "We don't even have a confirmed case in our community, so why do we do a full screening?" This is true from an individual point of view, but from the perspective of disease control, in the early stages of an unknown pathogen outbreak, large-scale screening is the fastest way to find out the chain of transmission and identify hidden infected people. At least until now, there is no more efficient alternative. In the past two years of high influenza season, many primary and secondary schools have organized influenza antigen screenings. Some parents thought, "It's just a cold, so why go all out to investigate?" However, the actual situation is that last year, a primary school did a whole-grade screening just after three fever cases occurred, and directly identified 12 asymptomatic infections. After home isolation, the entire school did not have a large-scale suspension of classes. If everyone had to wait until everyone had a fever before dealing with it, the consequences would be completely different.

Many people still have two common misunderstandings about screening. They either think that everything will be fine if they test negative, or they think the sky is falling if they test positive. A few months ago, a young man came for an AIDS test on the third day after engaging in high-risk behavior. He happily left after the result was negative. I chased him three times and shouted to him to retest in six weeks, but he didn't take it seriously. But on the seventh week, he showed up crying, and sure enough, he was positive - this is the pitfall of the "window period". After the pathogen enters the human body, it must replicate to a certain amount before it can be detected. No matter how many times during this period, the test was negative, it doesn't count at all. There was also a girl in her early twenties who tested positive for syphilis during her pre-marriage test. She sat at the triage table and cried for almost an hour, saying that she had never engaged in high-risk behaviors. However, further examination revealed that it was a false positive. During that time, she had an attack of lupus erythematosus, and her autoantibodies interfered with the test results, which was a false alarm.

I have been working in infection prevention and control for almost 8 years. People often ask me, "Do you think I should do screening for infectious diseases?" I never give a one-size-fits-all answer. If you have a regular physical examination every year, it won’t be a burden to add the four infectious diseases for more than 100 yuan. It is of course good to buy it and feel at ease. ； If you have recently had cosmetic surgery, dental repair, or engaged in high-risk behaviors, it is much better to take the initiative to get a corresponding screening than to think about it at home. ； As for the screening required during public health incidents, just cooperate and it will be done. After all, the logic of public health is never to take care of the convenience of one person, but to protect the safety of everyone.

To put it bluntly, infectious disease screening has never been a "scourge" or an "IQ tax". It is more like a small accident insurance we buy for our health. It costs a small amount to nip invisible risks in the bud.