The baffling spread of the novel coronavirus has given many scientists and policymakers pause. There may be some important clues in the patterns the disease is leaving that tell us quite a bit about what conditions can hasten its spread and even worsen its lethality. So far, the areas of the world where most people are dying of the disease – called the case-fatality rate – are densely populated cities in China and Iran.

Recent studies also confirm that air pollution has been blindingly severe in that region of northern Italy, where the coronavirus has been most virulent. The Lombardy region and the Po Valley in northern Italy rank among the most air polluted areas of Europe. Similarly, South Korean cities also suffer from levels of air pollution comparable to smoking cigarettes, and men there have one of the highest rates of tobacco smoking in the world.

In addition to China and Iran having some of the highest concentrations of human beings on the planet, there are a number of other important environmental factors in both regions that could explain why the disease seems more deadly in those locales. First, people living in Tehran or China’s Hebei province sometimes inhale the equivalent of a pack or more of cigarettes every day.

But while China has instituted national standards for air pollutants and taken the modern step of banning fireworks – one of the most severe forms of air pollution ever measured – monitoring is limited to cities. In fact, air pollution in major Chinese cities is declining. In Iran, conditions are worsening. The United Nations Environment Program ranks Iran 117 out of 133 countries with respect to overall environmental quality.

Especially in the wintertime, the air in these areas regularly can contain levels of ultrafine particulate air pollution from coal-burning and diesel engine products of incomplete combustion that would be illegal in most modern cities. The high levels of diesel pollutants around the world today are due to the millions of trucks and cars on the roads that rely on diesel engines that were fraudulently manufactured to pass emissions tests. These diesel vehicles came with their own defeater devices on all of the diesel engines produced in the 1980s. Whenever hooked up to a computer test, the engine would lower its emissions.

All this dirty air does not just clog vistas; it also clogs the lungs and the respiratory system. Basically, tiny pollutants 50 times smaller than a human hair can enter the lung and sometimes get into the bloodstream, compromising the immune system. Without normal healthy mucosa, the nose and lung lose the ability to slough off bacteria and viruses typically inhaled.

Lungs normally clear pollutants through the removal of viruses and bacteria by coughing. Healthy nose hairs also block the inhalation of pollutants. But chronic air pollution compromises the ability of the lungs to do their job. The natural mucociliary escalator dries up and cannot do its job of keeping us healthy.

Adding to this is the fact that basic sanitation in both Iran and China is dreadful. Specifically, public toilets often consist of squatting plumbing where you are not permitted to put toilet tissue down into the system. This means that bathrooms are surrounded with pieces of fecally contaminated toilet paper that may slosh around when water overflows.

Without question, in these regions, there are also massive general problems of sanitation and sewage, particularly around live-animal and slaughter markets such as the one where the coronavirus is believed to have originated in Wuhan that can also be found in Iran. These areas are also compromised by their very high population density and residential overcrowding. It is not unusual for adults that may not even be related to share beds. Many people sleep in their kitchens and dining rooms. In some factories where workers also live, there can be 8 to 10 in a single room.

Further compounding these situations, there’s a low level of vitamin D that comes about from the lack of sunlight. It is well known that those who live in the Northern Hemisphere tend to have lower levels of this essential nutrient. Those living in densely polluted regions will not have the opportunity for sunlight that causes the liver to produce this important disease-fighting vitamin. All of which suggests that the coronavirus may be much less of a problem in areas that are not as crowded, have better sanitation, and lower air pollution than in other zones.

This does not mean the United States shouldn’t be vigilant, but it does suggest that America may have less of a problem than have Italy, China, and Iran thus far. Because the virus appears to be more deadly for the elderly and because there is a two-week period when those carrying the virus can have no symptoms, there will be a need for quarantines wherever a case occurs. The most important thing people need to understand is that they should self-quarantine and not go to the doctors or clinics if they suspect they might have the new coronavirus or the flu.

Vigilance is required on all fronts. Prevention is always cheaper in the long run. We have to ask, do we want to pay later with an enormous loss of life and livelihoods, or should we invest now to maintain a healthier general environment so that we will have less to pay in the future?

Devra Davis is an epidemiologist and president, Environmental Health Trust.

Image credit: Shutterstock.com