LONDON, UK (GlobalData), 12 September 2012 - The Centers for Disease Control and Prevention (CDC) have announced that the United States is experiencing its worst epidemic of West Nile Virus (WNV) since the first US outbreak in 1999. The CDC reported that there have been almost 2,000 infections and nearly 90 deaths so far in 2012. However, to provide perspective, the National Weather Service reports that an average of 55 people are killed by lightning each year in the United States. In light of these statistics, it is worthwhile to ask - does this disease outbreak have the makings of a true epidemic, or is WNV caught up in a media whirlwind?
WNV is a mosquito-borne zoonotic virus that is transmitted from infected birds, the virus’ natural reservoir, to humans via mosquitos. Human-to-human transmission rarely occurs due to the inability of WNV to propagate effectively within humans. WNV should not be taken lightly, as the disease is capable of causing life-threatening infections, especially in the elderly, immunosuppressed, and very young children. But serious infections make up less than 1% of WNV cases, while approximately 80% of WNV infections are asymptomatic, and roughly 20% of WNV cases are associated only with a rash and flu-like symptoms (such as fever, vomiting, and aches). Treatment of WNV infections is currently limited to supportive care, such as the administration of intravenous fluids and respiratory support. This creates an opportunity for WNV therapies, but the low incidence and mortality associated with the disease makes the market unattractive for companies to undertake the significant funding needed to develop novel therapies. Companies with numerous antivirals, such as Gilead, could screen their compound libraries for molecules with anti-WNV activity, but the likely meager return on investment due to the low number of WNV-induced hospitalizations does not offer much of an incentive.
Large numbers of individuals are at an elevated risk of developing WNV-associated complications, including the 30 million Americans over the age of 65. This could make a WNV vaccine an attractive prospect, but unfortunately this age group does not respond well to most immunizations due to their weakened immune systems. Vaccines, especially for niche indications such as WNV, are not guaranteed to be successful commercial ventures.
GlaxoSmithKline’s experience with its Lyme disease vaccine, Lymerix, provides a cautionary tale for firms developing a WNV vaccine. Lyme disease, which is caused by the bacteria Borrelia burgdorferi, is transmitted via tick bites and has an incidence of approximately 20,000 infected per year within the United States (CDC). When Lymerix was approved by the FDA in 1998, it had $40m in revenue, but it was eventually withdrawn from the market in 2002 after demand decreased due to safety concerns. While side effects confound comparisons between Lymerix and any WNV vaccine, Lymerix’s failure still underscores the risks associated with developing therapies against low-incidence infections.
Insurance companies were unwilling to reimburse patients for Lymerix, and they are also unlikely to pay top dollar for a WNV vaccine, especially for patients less than 65 years old, thereby making this market even less enticing for Big Pharma. Small biotech firms, such as Hawaii Biotech, and academic researchers are trying to fill the void left by Big Pharma’s absence, but despite their efforts, a vaccine for WNV is still years away. In the meantime, precautionary measures, such as wearing long-sleeved shirts or using insect repellent, and increasing awareness will help limit the incidence of this disease. With smaller biotechnology firms taking the lead and risk, Big Pharma will likely lay low and in-license their way into this market once an attractive WNV therapy or vaccine emerges.
*Is West Nile Virus Truly Buzzworthy?
This expert insight was written by GlobalData infectious disease analyst, Dr Brad Tebbets. If you would like an analyst comment or to arrange an interview, please contact us on the details below.
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