Why should you care about bird flu?

Dr Samira Mubareka wearing a lab coat in a lab.
Dr. Samira Mubareka is a clinician scientist whose work focuses on emerging viruses. (Photo credit: Kevin van Paassen/Sunnybrook Health Sciences Centre)

Last week, the city of Brampton confirmed that two dead waterfowl found in the city had tested positive for highly pathogenic avian influenza (HPAI) virus, or bird flu. This follows earlier reports of cases detected in nearby Halton and Niagara Regions, adding the Greater Toronto Area to the growing list of places affected by the virus.

As its name implies, HPAI typically infects birds but since early 2022, there have been growing reports of mammals getting infected and dying of influenza infection across a large geographic area. These mammals range from small land animals like raccoons and skunks to large carnivores like bears and mountain lions, as well as marine mammals like sea lions and dolphins. The illnesses are caused by the H5N1 strain of bird flu that is currently circulating across multiple continents.

To learn more about the bird flu outbreak and what we can do to prepare, I spoke to Dr. Samira Mubareka, an infectious diseases physician, medical microbiologist and scientist at Sunnybrook Research Institute. She is also an associate professor in the department of laboratory medicine and pathobiology in the Temerty Faculty of Medicine at the University of Toronto. Her research uses a collaborative One Health approach to conduct surveillance in wildlife and look at the biology of emerging viruses and transmission between species, including humans.

BZ: How widespread is bird flu right now?

SM: The level of avian influenza activity we’re seeing at the moment is unprecedented. To step back a bit, the first cases in North America were reported in late 2021 in birds in Newfoundland, and from there, it spread along the eastern seaboard into the United States along Atlantic flyways. Subsequently there were cases reported in the west of Canada and the United States, followed by cases in Central and South America. Beyond affecting wild and farmed birds, we are seeing spillover of HPAI into mammals, many of whom die of severe neurological complications. There has also been renewed focus on HPAI because a reported outbreak among farmed mink in Spain, with mammal-to-mammal transmission, and large die-offs of marine mammals, including sea lions. The virus also appears to be reassorting, or exchanging genetic material among H5N1 lineages. All of these represent red flags that reflect an amount of viral activity that we really haven’t seen before. We’ve also never seen this level of bird depopulation, both from die-offs and as a control measure. This has potential to impact biodiversity, wildlife health and conservation, as well as food costs and security. There have been a significant number of outbreaks, including here in Ontario, and some of them have been fairly close to densely populated areas. Having said all this, it is important to underscore that the risk remains low for humans, and that we have not had any human cases in Canada. Regardless, we need to prepare for that possibility.

Continue reading

Asymptomatic dengue-infected humans can transmit the virus to mosquitoes

A drawing of a female Aedes aegypti mosquito (Credit: E.A. Goeldi)

An estimated 3.9 billion people in 128 countries are at risk of dengue virus infection. Of the estimated 390 million dengue infections that occur each year, 96 million will manifest clinically with flu-like symptoms including fever, headache, nausea and muscle and joint pain. Unlike the flu virus, dengue virus cannot be transmitted directly from person to person. It instead relies on an insect vector, the mosquito Aedes aegypti. Female mosquitoes contract the virus when they bite and feed on an infected human. After a period of four to ten days, the virus disseminates to various tissues in the mosquito, where it remains for the rest of the mosquito’s life. At this point, the mosquito is infectious and can transmit the virus through its saliva and bite.

Earlier studies showed that the time during which dengue virus-infected humans can transmit the virus to mosquitoes coincides with the onset of clinical symptoms and an increase in viral load in their blood. These observations led to the assumption that infected, asymptomatic humans are so-called “dead-end hosts” for the virus because their viral levels are so low as to make them noninfectious to mosquitoes, essentially breaking the transmission chain.

In a new paper published last week in the Proceedings of the National Academy of Sciences, an international group of researchers challenged a long-held assumption that asymptomatic patients infected with the dengue virus are not infectious. The team sought to experimentally test the assumption that asymptomatic people are noninfectious and to determine how human-to-mosquito transmission varied with timing of symptom onset. Continue reading

Integrating self-collecting HPV DNA testing with community health worker programs increases cervical screening coverage

This past weekend, I attended a conference on health and high politics examining the role of politics, global partnerships, and innovation in health equity and security. Two talks at the end of the day stood out for me. The first was by Dr. Leslie Davidson, a professor of epidemiology and pediatrics at Columbia University, and the second was by Dr. Ophira Ginsburg, a medical oncologist at Women’s College Research Institute in Toronto who specializes in women’s health equity and global cancer control.

A common thread in both talks was the increasingly important role of community health workers in meeting the challenges of delivering health services to underserved populations. During Dr. Davidson’s talk, she mentioned a recently published study from Argentina demonstrating the effectiveness of using community health workers as part of an integrative program to promote cervical cancer screening. Ever intrigued, I decided to read the original paper and share it here.

In the study published in Lancet Global Health, researchers found that when community health workers offered self-collecting HPV tests to women, participation rates increased four-fold. Human papillomavirus, or HPV, DNA testing is emerging as a viable alternative to Pap smears in low-resource settings. Earlier studies have shown that HPV DNA testing is as sensitive as conventional Pap smears in detecting cervical disease. An additional benefit of HPV DNA testing is the potential for self-sampling, which allows women to collect their own vaginal swabs in the comfort of their own homes. Continue reading