Big Game Virus Hunting with Covid-19

Africa, the Mother Continent, Cradle of Mankind, is home to more large mammal species than anywhere on earth.

It is critical to protect and preserve these amazing creatures for their biodiversity and the benefit of future generations, not to mention their importance to tourism. No one should want to hurt such impressive animals, but everyone wants to protect themselves from viruses. Wild animals no longer threaten most humans. Novel viruses do.

As a viral disease researcher, trained to fight invisibly small viruses, I imagine how waging war against deadly microbes might compare to hunting nature’s biggest, most dangerous animals. Could one imagine shooting a virus with a tranquilizerdart to stop them in their tracks?

If viruses were big game, the worst viruses would be potentially the most dangerous animals. Ebola would be the elephant. Ebola’s closest viral relative Marburg virus, the only other member of the filovirus family, would be the Rhinoceros. As dangerous as elephants and rhinos can be, untreated, both Ebola and Marburg kill 90% of those they infect. Another virus just as deadly is Hantan virus, named after Hantan province in China. Ebola, Marburg, and Hantan viruses are all haemorrhagic fever viruses that kill approximately 90% of those they infect. Compare Hantan to a hippopotamus. The hippo, the deadliest animal in Africa, annually kills more than any other.

Next to rabies that kills 100% of those it infects, HIV is the deadliest virus. Untreated, HIV eventually kills 98% to 100% of those infected. The primary difference is that HIV is a lentivirus - a “slow” virus. While most deadly viruses kill within two to four weeks after infection, HIV takes between six and sixteen years to kill in most cases, mostly depending on the clade or species of HIV a person is infected with. Slow yes; but just as deadly in the end. HIV is comparable to the African buffalo, the second most deadly wild animal in Africa.

Lassa fever and yellow fever are caused by two haemorrhagic fever viruses endemic in West Africa. Compared to the above-mentioned viruses, Lassa and yellow fever are not nearly as deadly. Lassa kills only 1% and yellow fever kills 3-7% of those it infects, so Lassa and yellow fever might be the zebra and wildebeest of viruses. Those are dangerous in large herds but not so much as lone animals.

And influenza? That would be a warthog. Influenza normally kills .25 to .35% of those infected annually. Influenza kills tens of thousands each year in America alone. It would kill many more if people did not get their annual flu shots.

What animal would SARS-CoV-2 that causes Covid-19 be? How about a Kudu, an imposingly large deerlike animal with long curved horns? A kudu is unpredictable and could kill you, but more likely will walk away calmy into the bush. As scientists and doctors have gained greater insights into how to treat Covid-19 and the average age of those infected has fallen, the case fatality rate also has fallen from as high as 7% in Italy early in the pandemic to the range of 0.65% to 2.5% now prevailing in many countries. That makes Covid-19 two to ten times as deadly as influenza.

So how can one slow down a charging wild animal, or a viral infection raging out of control? Most doctors and governments are still baffled about how best to tackle SARSCoV- 2, the most recent assailant emerging from the viral world. Most hunters or game wardens know how to stop a dangerous wild animal in its tracks – a gun. Since no one should want to harm one of nature’s most magnificent creatures, a tranquiller gun is preferable. Shooting a tranquilizer dart into a big game animal slows it down and harmlessly puts it to sleep. If only we could do the same to viral invaders. Fortunately, there is a way to do that although it may not work as well or as perfectly as a tranquilizer dart. What could that be?

Every doctor and most mothers know about inflammation. Most infections cause inflammation in the tissues they affect. Inflammation is a sign the most primitive part of the immune system is fighting against a germ or virus. It is the first, non-specific response of the immune system, before the more sophisticated cellular response has time to kick in. Inflammation causes pain and swelling.

Viral infections cause an inflammatory response. Too much inflammation severely damages tissues and organs, so controlling inflammation is important.

The immune system regulates the immune response by releasing chemical messenger signals in the body. Some messenger signals increase inflammation. Others reduce it. While viral infection causes inflammation, inflammation also increases viral replication. This is the trick viruses use to stimulate their own replication, resulting in a vicious circle. The challenge for doctors is to know how to cut this cycle, what scientists call a positive feedback loop. There is a simple way to do this – anti-inflammatories. Not all anti-inflammatories do this, but certain ones reduce both inflammation and viral replication. Which ones?

Continues next week….

Howard Armistead is the Director of the Selenium Education and Research Centre in Johannesburg, South Africa