By looking back at 2013, can we learn anything about what to expect going forward in the realm of infectious diseases? There’s some bad and good news.
I tell my graduate students at UC Berkeley that I believe one of the greatest threats to our way of life is an outbreak of one or more pandemic infectious diseases. Think about the influenza pandemic of 1918–1919, when between 50 and 80 million people died within a one-year period of time. Even Hitler and Stalin combined could not match that rate of killing.
Two infectious diseases that emerged during the last year continue to keep me up at night worrying: MERS and Influenza H7N9.
- MERS stands for Middle Eastern Respiratory Syndrome and is caused by a virus related to the one that in 2003 launched the SARS epidemic. So far there have been less than 200 cases but almost half of those patients have died. The illness has remained confined primarily to Saudi Arabia and nearby countries. But, we have yet to learn how it spreads and what animal host represents its primary home (in medical parlance, its reservoir). There’s no vaccine or treatment; patients either recover, or they don’t.
- Influenza H7N9 is a new strain of avian flu that was only identified in humans early in 2013. Unlike other strains of avian flu, the current outbreak has been detected more often in humans than birds. Like MERS, it has caused only a few human cases, about 150. And, also like MERS, it leads to an unusually high mortality rate—about 40 percent. There’s no vaccine, although it is possible that one of our existing anti-influenza drugs may help.
It’s likely that neither of these viruses will wreak international havoc, but we have no way to know that for sure—or to predict with any degree of certainty what will happen. We also don’t know what other previously unrecognized pathogens might suddenly break into human populations.
On the brighter side, the quadrivalent HPV vaccine—to prevent cervical cancer—is a real success story. (Two HPV vaccines are available: the quadrivalent contains four types of HPV antigens, the two most often associated with cancer and the two most often associated with genital warts. The bivalent vaccine only focuses on cancer-causing types of HPV.) In countries that have widely accepted it (such as Australia) there are fewer cases of pre-cancerous cervical changes, as well as genital warts.
At the same time, the quadrivalent HPV vaccine also helps to prevent infection among the un-vaccinated because of what epidemiologists call “herd immunity”—the idea that when enough people in a group are vaccinated, it confers immunity on the entire population, or herd. I hope we’ll see big increases in the use of this vaccine in the US. To date, the numbers have been disappointing.
And, I think the award for the most hopeful news of 2013 is shared by the expectation that polio eradication will occur within the decade and that a cure is in sight for patients with chronic infection with chronic hepatitis C.
- There is a real and realistic plan to eliminate polio. In spite of the recent setbacks, including the harassment and sometimes murder of vaccine workers, we are starting to glimpse what a world free of polio will look like. India is the poster child: even with its poverty and limited infrastructure, there have been no cases of polio in over two years.
- There is now hope for a “cure” from chronic hepatitis C. This is a huge problem and a terrible disease. About 1 to 3 percent of the worldwide population is infected (approximately 175 million people, with 3 to 4 million people newly infected each year). Of those infected, 20 to 30 percent will develop cirrhosis and liver failure, and 2 to 5 percent will advance to liver cancer. This last year saw the rollout of several very effective and much less toxic therapies. These new drugs show real promise for curing infection—a real first.
Early in my medical training, we entertained the naïve belief that the world was on the verge of eliminating infectious diseases. That’s not going to happen any time soon—or ever. But we have made real progress. In spite of newly emerging diseases like MERS and influenza H7N9, we continue to make progress with our vaccines and therapies. I cannot let go of my fears about emerging infectious diseases but I’m cautiously optimistic about next year and beyond.