Why the “zero patient” quest and tracking disease outbreaks are so complex

It is important to track the source of the disease.

It answers questions about when and how people first get sick, and helps delay the spread of infections both in current and future outbreaks.

But Recent exposure to Victoria’s Coronavirus Hotel Quarantine Program The heart of the devastating COVID-19 wave in the state reminds us that outbreaks often occur. More complex than it looks..

So what is the value of trying to find a “zero patient”? What else should I consider when tracking an outbreak?

“Patient Zero” has a different meaning

Patient zero is commonly understood to mean the first case of disease outbreak, but the term is often applied in a variety of ways.

In the case of zoonosis (a disease that jumps from animal to human like SARS-CoV-2), patient 0 may refer to the first human case, the point where the virus spills from animal to human. There is.

In popular culture, zero patient is often used to refer to the first case in a particular area, or to the attention of a health authority.

These are not always the same.

“The first case informed us may not be the first case of an outbreak,” said Brett Sutton, chief health officer of Victoria last month.

Similarly, just because someone is identified as the first case does not mean that the disease has infected or irresponsibly acted on others. It’s like a coronavirus, and you might not even know you’re sick.

This is part of why Zero Patient is not a term that epidemiologists and public health professionals tend to use — not specific enough.

They like words Index case Authorities mention the first person to notice in the outbreak, which gives them a clue as to what is going on, and Primary incident A person who introduces a disease into a new group: a community, a country, or the world.

In some cases, the primary case and the index case can be the same person, but not necessarily. In many outbreaks such as HIV/AIDS, and in some cases COVID-19, the main case cannot be known.

Understand how the disease spreads

Although the use of the term zero patient can be confusing, tracing outbreaks back to their beginning is still important in public health.

Raina Macintyre, Head of Biosecurity at UNSW’s Kirby Research Institute, said that in the early stages of the outbreak, it is still possible to catch the sick embers before the embers have burned out.

“We can counteract them by actually identifying all cases, tracking all contacts, isolating them and making sure they don’t grow any further,” says Macintyre.

But even after the first few days or weeks of significance, tracking cases to zero patients can provide useful insight into how the disease is spreading.

After the cholera outbreak in Haiti in 2010 and the death of more than 9,000 people, epidemiologists traced a series of disease transmissions to the first few cases.

Louise Ivers, a research-led infectious disease doctor, helps researchers understand how the disease has spread, and that medical services and appropriate hygiene systems help reduce the spread of cholera. He said he reaffirmed his role.

“It is very important to understand the structures, systems, and problems that cause the outbreak,” said Dr. Ivers, an associate professor of international health at Harvard University. ..

“It’s usually the purpose of trying to understand the index case or the first case… I’d like to establish an opportunity to learn from this and try to prevent it from happening again.”

Blame game danger

The term zero patient first appeared in the United States in the 1980s when researchers were trying to understand how HIV / AIDS was prevalent in the community.

In a study examining sexual contact in gay men infected with AIDS, researchers classified one of the sexual networks as patient “O”. This represents outside California. They were placed in the center of the figure and linked to some other cases.

The letter O was later mistaken for the number 0.

It was later revealed that this zero patient was Gaetandugas, a French Canadian flight attendant. He was then and falsely accused of causing the epidemic of National AIDS.

Researchers never suggested that dugas was the cause of the outbreak, and studies confirmed that the virus had spread long before it entered the United States, but the idea of ​​zero patients persisted.

In the case of Douga, the label has perpetuated the idea of ​​stigma and shame, creating opportunities for scapegoating and criticism.

And today we see that the same problem is occurring with coronaviruses.

February, World Health Organization Give a warning About the risk of social stigma related to COVID-19 diagnosis. They say that stigma and blame encourage people to hide their illness and avoid testing, making it even more difficult to spot the outbreak.

See the big picture

Disease outbreaks, irrespective of how fascinating the story may seem, are rarely simplified to a single index case.

Rather, outbreaks are a “combination of infectious agents and the social circumstances they are in,” Dr. Ivers says.

This is a story that has been repeated many times throughout history, from the 1918 flu to HIV/AIDS and now to the coronavirus. Treatment of outbreaks varies by country. In other words, the introduction of the same disease can have very different results.

When thinking about Patient Zero in the context of COVID-19, focusing on who is not so important—but how and why?

Scientists have warned for decades that a pandemic like ours will happen, Thanks to the continued expansion of human animals into their natural habitats.

It takes only one jump from animal to human to start a new deadly disease.

It starts from one person. But how that happens-if it happens at all-depends on more.