CLINICAL MATTERS
A couple of weeks ago, a good friend from my infectious diseases fellowship days in the United States sent me a link to a post about an “undiagnosed pneumonia outbreak” in China. She was quite distraught and said she couldn’t handle another pandemic. I looked over the link and true enough, the poster was a well-known epidemiologist with a penchant for hyperbole. I reassured my friend that more likely than not, this was the usual alarmist news and that there was nothing unusual about respiratory illness spikes at this time of year. In fact, the United States had a severe “tridemic” of influenza, RSV (respiratory syncytial virus) and Covid-19 at around the same time last year and no one suggested anything about a “new mysterious illness” that might jeopardize our world anew at that time.
This kind of Sinophobic bias has reared its ugly head multiple times during the pandemic and I expect it will continue to do so.
Nevertheless, I decided to do due diligence to find out what was going on. A little bit of digging showed that the World Health Organization had requested and received information from China on their new outbreak. The verdict was that the cause of the spike in illness was from known pathogens—influenza, RSV, Covid-19, and Mycoplasma. Not content with this mundane explanation, the usual fear mongers played up the unfamiliarity of the general public with Mycoplasma and went overtime producing posts and graphics showing the spread of a “nightmare pathogen” which was widely shared.
For medical doctors, Mycoplasma is a familiar organism that we learn about in medical school. It is certainly not a nightmare pathogen and is generally associated with mild disease. Mycoplasma, along with Chlamydophila and Legionella are the most common causes of what is known as “atypical pneumonias.” These are responsible for up to one third of bacterial pneumonias and may need antibiotic treatment to help with recovery.
Pneumonia is a generic term that refers to an infection of the lower respiratory tract. The lower respiratory tract includes the lungs and the bronchi. Many different pathogens can cause pneumonia, including viruses, bacteria, and fungi. Patients with pneumonia typically develop fever, cough, and sometimes chest pain especially when coughing. A chest x-ray usually shows some abnormality in the lungs, typically an “infiltrate” which is a hazy area where there is infection, inflammation and secretions.
Until recently, with the increasing availability of PCR, most viral pneumonias were difficult to diagnose. Most resolved on their own without treatment, although some people could develop severe pneumonia—as seen with SARS, MERS, and Covid-19.
Most viral pneumonias are also accompanied by an upper respiratory tract infection (URTI) where the virus invades the throat and sinuses and then sometimes make their way into deeper lung tissue. Most viral URTIs do not progress to pneumonia and get better on their own.
Bacterial pneumonias in general tend to be more serious than viral pneumonias. Since they are caused by bacteria, these pneumonias can be treated with antibiotics. Bacterial pneumonias are divided into community-acquired and hospital-acquired pneumonias. Community-acquired pneumonias (CAP) are commonly caused by bacteria living in our throat and nostrils. The most common bacterial cause of CAP is Streptococcus pneumoniae. Streptococcus pneumoniae used to be called Pneumococcus and so doctors tend to refer to pneumonias caused by this bacteria as pneumococcal pneumonia. CAP, depending on its severity, is divided into low risk, moderate risk and high risk. Low risk CAP can be treated with oral antibiotics at home, while someone with moderate risk CAP needs to be admitted to the hospital for IV antibiotics. High risk CAP which sometimes requires mechanical ventilation is usually treated in the ICU.
Pneumococcal pneumonia, along with two other common bacterial pathogens Moraxella catarrhalis and Haemophilus influenzae causes what is known as “typical pneumonia” where the severity of the infiltrates on x-ray usually correlates to the severity of illness. In contrast, atypical pneumonias including those from Mycoplasma can show very scary, extensive infiltrates even if someone has mild symptoms. This phenomenon gave rise to the term “walking pneumonia” which is another name for atypical pneumonias since people with pretty bad xrays can still be walking around, unlike in those with the typical pathogens who would be pretty sick if that much lung was infected and involved. So in a way, Mycoplasma is really a less severe form of pneumonia compared to the other typical pathogens and is far from a “nightmare.” Having said that, an atypical pneumonia can still cause severe disease especially in the elderly and vulnerable populations.
Treatment of Mycoplasma is typically included in the treatment for CAP. For instance, using a macrolide like azithromycin for low-risk CAP will cover both Streptococcus pneumoniae and atypical pathogens. For a more serious moderate risk CAP, we use an IV antibiotic like ceftriaxone which works very well against Streptococcus pneumonia, but we still add the azithromycin just in case there is also Mycoplasma or the other atypical pneumonia organisms. None of the penicillins and their related beta-lactam antibiotics like the cephalosporins or carbapenems have any activity against Mycoplasma because, unlike most bacteria, Mycoplasma has no cell wall. Penicillin and other beta-lactams target the cell wall and so they don’t work against Mycoplasma. There are other antibiotic classes that can be used to treat Mycoplasma, including tetracyclines and fluoroquinolones. Don’t take antibiotics without talking to your doctor, because it may not be appropriate for what you have.
It is nearly impossible to tell what the causative agent of a cold or a cough is based on symptoms. This is why it is very important to see your doctor if you feel sick. Some cough and colds are just URTIs while some can be full-blown pneumonias. Your doctor knows what tests to do to figure this out. Potential danger signs include shortness of breath, low oxygen levels, prolonged high fever, chest pain, and coughing up bloody phlegm. If you have any of these signs, you should go to the emergency room.
There are many things one can do to decrease the chances of getting sick with a respiratory illness. Covid-19 vaccines, flu vaccines, and pneumonia vaccines are available. Ask your doctor if you need one. RSV vaccines will soon be available for the general population as well. Good ventilation and avoiding indoor crowds is always a good idea. But one of the most effective and simplest thing one can do is still to wearing a mask. If you are sick, wear a mask. If you are in the vulnerable population, wear a mask. If you live with someone in the vulnerable population, wear a mask. Even if you are none of the above, wear a mask. No one wants to cough and sneeze and feel sick especially this holiday season. And the last thing you want to give someone for Christmas is the flu.