Wednesday, 26 December 2018

All infectious diseases are seasonal


Most of us are aware of the seasonal cycle of influenza outbreaks, which for Americans peak in the winter. In a new paper, Micaela Martinez, PhD, a scientist at the Columbia Mailman School of Public Health, makes a case that all infectious diseases have a seasonal element. The "Pearl" article appears in the journal PLOS Pathogens.

Martinez collected information from the World Health Organization, the U.S. Centers for Disease Control and Prevention, and peer-reviewed publications to create a calendar of epidemics for 69 infectious diseases, from commonplace infections to rare tropical diseases. A given year will see outbreaks of flu in the winter, chickenpox in the spring, and gonorrhea and polio in the summer -- to name a few of the best described seasonal outbreaks.

She found seasonality occurs not just in acute infectious diseases like flu but also chronic infectious diseases like Hepatitis B, which depending on geography, flares up with greater regularity certain times of the year. Preliminary work has shown that even HIV-AIDS has a seasonal element, thought to be driven by seasonal changes in malnutrition in agricultural settings.


The paper describes four main drivers of seasonality in infectious diseases. Environmental factors like temperature and humidity regulate seasonal flu; in vector-borne diseases like Zika too, the environment plays a role in the proliferation of mosquitos. Host behaviors such as children coming into close proximity with each other during the school year are a factor in measles. Ecological factors such as algae play a role the outbreak of cholera. Seasonal biological rhythms, similar to those that govern migration and hibernation in animals, may also be a factor in diseases like polio, although more research is needed.

See:

Micaela Elvira Martinez. The calendar of epidemics: Seasonal cycles of infectious diseases. PLOS Pathogens, 2018; 14 (11): e1007327 DOI: 10.1371/journal.ppat.1007327

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology

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