As coronavirus continues to spread and scientists project how many people are likely to be infected, there has been much talk of contagion. It is easy to imagine red streaks that trace the path of illness extending across the globe like in a Hollywood movie.

Predictably, conspiracy theories about coronavirus have spread alongside the virus itself. Thousands of social media accounts linked to Russia claim the US created the coronavirus to “wage economic war on China”, and a US senator repeated a rumour that it began in a Chinese bio-weapons lab and not an outdoor market.

Governments have resorted to conspiracy theories to distract from their own failures or to pre-empt criticism

When explaining why conspiracy theories spread, people often reach for metaphors of viral contagion. And in certain respects, these can indeed be helpful. Long before Twitter existed, people would share information of uncertain veracity – otherwise known as rumours – as a survival mechanism. In the presence of an urgent threat, it was rational to collect all available information and pass it on. Through chains of transmission, masses of people distant from the initial event could be “infected” with misinformation – sometimes with devastating consequences. Now, with the rise of social media, false rumours can spread even more rapidly.

But the analogy between the spread of disease and the “virality” of conspiracy theories is misleading in two critical ways. First, ideas can spread without direct contact. Whereas information once travelled from person to person, as diseases still do, since the advent of print capitalism people have been able to propagate dodgy ideas through the written word. Today, the mass media enable certain individuals to spread conspiracy theories far and wide. Anyone who is lucky enough to have a newspaper column, radio show or Twitter account with a large following can reach extraordinary numbers of people.

Second, people who spread conspiracy theories are not passive conduits. Unlike the carriers of an illness, they actively seek to spread them. Whereas viruses can kill, conspiracy theories, when deliberately spread by powerful actors, can cause a different type of harm: they erode political accountability. In this way, conspiracy theories can be weaponised to weaken the body politic, as if a group of people had the ability to take the common cold and turn it into Ebola.

Facebook Twitter Pinterest ‘A fictional narrative’ … President Trump and Ukrainian president Volodymyr Zelensky. Photograph: Saul Loeb/AFP via Getty Images

Take the recent impeachment hearings in the US. Witness testimony and the memo of the US president’s “perfect call” established that Donald Trump wanted the Ukrainian president, Volodymyr Zelensky, to investigate Ukraine’s supposed interference in the 2016 election. This “fictional narrative” that Ukraine, not Russia, meddled in the election was initially pushed by the Kremlin and found favour among a small fringe of Trump supporters on social media.

But when Trump’s defenders needed a counter-narrative to explain why he summarily suspended military aid to Ukraine, the conspiracy theory blaming Ukraine fit the bill. Despite the consensus of the US intelligence community that Russia alone had meddled, prominent Trump allies with large public platforms, including Senator Ted Cruz, Fox News pundits and other Trump administration surrogates, voiced some version of the conspiracy theory.

After the Ukraine canard was promoted by these public figures, it spread horizontally among Trump’s supporters (and some automated bots) on Twitter in ways that resemble conventional contagion. But its rapid ascendancy owed more to the concerted efforts of influential people intent on promoting lies for the sake of political expediency, rather than to passive transmission.

Coronavirus has many elements that make it prime material for conspiracy theories. Invisible to the naked eye, viruses have long caused fear and panic. Now add geopolitics to the mix: China’s growing economic and political influence is already a source of anxiety among its neighbours and rival countries. The classic conspiracy theorist’s question is, who benefits from this? And in the case of coronavirus, there are plenty who could gain from China’s plight (although those benefits will weaken as more and more countries become affected). Finally, as the virus spreads, some governments will be tempted to cover up bad news, providing the kernel of truth that conspiracy theories thrive on.

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But the reach of any conspiracy theory will depend in part on who sees political advantage in spreading it – and how much influence those people have. As the coronavirus spreads to new countries, governments have resorted to conspiracy theories to distract from their own failures or to pre-empt criticism. They may target existing foes, as with Trump blaming the media for deliberately “panicking markets”. Other governments might find them attractive as a way to deflect blame. President Rouhani of Iran, for example, called reports of the country’s struggles to contain the virus “one of the enemy’s plots to bring our country into closure by spreading panic”. China, meanwhile, has resorted to inflaming nationalist grievances to change the subject and has previously shown itself willing to use conspiracy theories for cynical purposes, such as in relation to the Hong Kong protests.

In an age of extreme connectivity, we are exposed to more new ideas than ever but we are also vulnerable to manipulation. Conspiracy theories promoted for political gain do not kill like viruses do, but by infecting the public discourse with false or harmful ideas, they make it harder for citizens to ascertain the truth and hold politicians accountable. And unlike biological organisms that cause illness only as a byproduct of their need to survive, the people who knowingly promote conspiracy theories do so with the very purpose of weakening the host.

• Scott Radnitz is an associate professor at the Jackson School of International Studies and director of the Ellison Center at the University of Washington. He is writing a book on post-Soviet conspiracy theories