What is patient zero

The search for 'patient zero' and why tracing disease outbreaks is so complicated. It helps us to answer questions about how and when people first become sick, and to slow the spread of infection, both now and in future outbreaks.

But recent revelations about Victoria's coronavirus hotel quarantine program at the centre of the state's devastating COVID wave are a reminder that outbreaks are often more complicated than they seem. So what's the value in trying to find "patient zero"? And what else needs to be considered when tracing a disease outbreak? Patient zero is generally taken to mean the first case in a disease outbreak — but the term is often applied in different ways.

When it comes to zoonotic diseases ones that jump from animals to humans, like SARS-CoV-2 , patient zero might refer to the first-ever human case — the point at which the virus spills over from an animal to a human. In popular culture, patient zero is often used to refer to the first case in a particular region, or the first case that's come to the attention of health authorities. Similarly, just because someone is identified as the first case doesn't mean they spread the disease to anyone else, or behaved irresponsibly — with something like coronavirus, they may not even know they're sick.

This is part of the reason why patient zero is not a term epidemiologists or public health experts tend to use — it's not specific enough. They prefer the term index case to refer to the first person authorities became aware of in an outbreak which gives them a clue something's going on , and primary case to refer to the person who introduces a disease into a new population — a community, country or the world.

Sometimes, the primary case and the index case will be the same person, but not always. While the use of the term patient zero can be fraught, tracing outbreaks back to their beginnings remains important in public health. In the early days of an outbreak, it's still possible to catch embers of disease before they become full-blown fires, says Raina Macintyre, head of biosecurity at UNSW's Kirby Institute.

But even after those critical first days or weeks, tracing cases back to patient zero can still give us useful insights into how disease spreads. In the aftermath of the cholera outbreak in Haiti, which killed more than 9, people, epidemiologists traced the chain of disease transmission back to some of the very first cases. Second, according to the US NIH website, research has shown evidence of infection in five states appeared back in December Third, US government officials sealed blood samples collected before January 2, from further testing on national security grounds.

Fourth, Florida had published data of early cases occurred in January and February , only for the related data to be later removed. Fifth, there were around netizens from the US or countries connected to the US claiming that they or others suspected that they were infected with COVID as early as November The Ebola outbreak that swept across West Africa has been traced to a young boy from Guinea who is thought to have caught the virus from bats Credit: Getty Images.

Scientists concluded this outbreak of a new strain of Ebola started with just one person — a two-year-old boy from Guinea — who may have been infected by playing in a hollow tree housing a colony of bats. They made the connection on an expedition to the boy's village, Meliandou, taking samples and chatting to locals to find out more about the Ebola outbreak's source before publishing their findings.

Originally from Ireland, Mallon emigrated to the US, where she began working for rich families as a cook. After clusters of typhoid cases among wealthy families in New York, doctors traced the outbreak to Mallon. Anywhere she worked, members of the household started to develop typhoid fever.

Doctors called her a healthy carrier — someone infected by a disease but who display little or no symptoms of the disease, which means they often go on to infect many other people.

There is now growing evidence that some people are more "efficient" than others at spreading viruses and Mallon is one of the earliest recorded cases of a person having this "ability" known as a "super-spreader".

Many health experts are against identifying the first documented case of an outbreak, for fear that it might lead to disinformation about the disease or even victimisation of the person. Gaetan Dugas, a Canadian homosexual flight attendant, is one of the most demonised patients in history, being blamed for spreading HIV to the US in the s.

But three decades later, scientists revealed he couldn't be the first case — a study showed the virus had moved from the Caribbean to America at the beginning of the s. Style: MLA. Get Word of the Day daily email! Test Your Vocabulary. Can you spell these 10 commonly misspelled words? Love words? Need even more definitions? Homophones, Homographs, and Homonyms The same, but different.